A properly painted concrete block wall will be virtually maintenance free for many years, but the same wall not properly painted can be a maintenance nightmare. There are just a few critical differences between a good and a bad paint job.
The main considerations you need to think about are new and unpainted, condition of existing finish and type of concrete block. All of these will require similar approaches when preparing the block for the protective finish coat.
You will encounter two types of block, smooth and split-face. The difference of texture will drastically alter the amount of primer and finish paint needed. Count on split-face block needing twice as muck primer and paint when compared to smooth block. Exterior block surfaces can be either, but interior block surfaces are always smooth.
Preparing the Concrete Block For Painting
Painting concrete block walls always starts with the removal of dust and dirt, efflorescence, and all loose or peeling paint. Both interior and exterior block surfaces require the same attention to details.
Efflorescence Deposits
Plain water will remove loose paint and dirt but efflorescence will need chemicals to be neutralized. Efflorescence is a white powder that can form on the concrete block and is caused by water infiltration inside the block.
Can be caused by failing exterior paint, a leaking roof or metal cap flashing. Use acidic masonry cleaner to remove this unsightly mess. On interior surfaces use a scrub brush to fully remove stubborn deposits. While pressure washing the exterior inject the masonry cleaner into the washer and use a scrub broom on persistent areas.
After removing the efflorescence deposits find out were the water leak(s) came from and make any repairs necessary.
Interior Preparation
New unpainted concrete block walls need to have all dirt and loose mortar removed prior to priming. Painted walls will need all loose and peeling paint removed. Lift off the peeling paint with a stiff putty knife or paint scraper. Then scrub the area with a wire brush.
Also, any greasy or oily deposits will need to be cleaned with TSP, trisodium phosphate, and primed with a stain blocking primer.
Exterior Preparation
The first step when preparing concrete block walls is pressure washing. Use a commercial style pressure washer and at least 2500 psi. A suitable spray pattern is the 15° degree tip held 12 inches from the surface. Any remaining loose paint will need to be removed manually.
During the preparation pay attention to any loose mortar and large cracks. All repairs need to be done after the pressure washing.
Pressure Washing
A good washing will save a lot of time later. Don’t rush, it’s easier to pressure wash than manually scrape the loose paint.
- New and Unpainted – All your after is removing any dust, dirt and loose chunks of mortar. Mild pressure, 1500—2000 psi, is all that is needed. Work in a horizontal, back and forth, pattern. Start washing at the top and work your way down the concrete block wall.
- Previously Painted – Most of the prep-work involves removing all loose or peeling paint and fully evaluating the condition of the block. The pressure washer can remove most, if not all, of the loose paint. To remove the majority of peeling paint with a pressure washer use 2500-psi and 15° degree spray tip, typically white. Hold the tip 12 inches from the surface and work in a horizontal, back and forth, pattern.If any paint peels during the washing continue following the edge of the loose paint. Try to inject the water underneath to lift as much as possible. The spray tip can be within 6—8 inches of the surface to concentrate the water pressure. Follow this procedure with a vertical washing pattern.
In order to provide the most adhesion and best performance, all caulking needs to take place after the application of primer. You have many choices, as which to use.
The best types of caulk are elastomeric and polyurethane. Use non-sagging polyurethane for expansion joints and elastomeric around windows and doors.
Materials needed for caulking expansion joints are foam backer-rod and non-sagging polyurethane caulk. The backer-rod needs to be slightly thicker than the expansion joint, example- a 3/4 inch joint needs 1 inch foam backer-rod.
Insert the backer-rod 1/2—3/4 of an inch below the surface. Polyurethane sealants are very sticky and reduced with mineral spirits. Use a plastic spoon and mineral spirits to tool and smooth the sealant.
Caulking windows and doors is the same on a concrete block building as with caulking any interior or exterior surface.
Choosing the Primer and Paint
Primer
Unpainted concrete block needs to be primed before the application of the finish paint. The main function of the primer is to fill the pores and neutralize the high P.H. The best primer designed for this purpose is Acrylic Block Fill.
Typical coverage for Block Fill is 200 square feet per gallon on smooth block and 100 square feet on split-face block.
Acrylic Block Fill primer can be applied over acrylic or latex painted concrete block when properly cleaned and prepared. Many manufactures also produce an oil base formula for use over oil base finishes. This can resolve prior defects in paint jobs that were never properly primed and have open pores.
Paint
Any high quality paint can be applied over Block Fill primer, but certain types perform better over time. The absolute best for exterior use is Elastomeric paint. This finish can outlast normal paint 2—1. The next best choice is 100% Acrylic semi-gloss or satin sheen paint. Interior surfaces can receive any sheen to match your decor.
Acrylic paints will out last standard oil base finishes when use on the exterior. With interiors your paint choice depends on the use of the wall, room or area. Finishes with a higher sheen, semi-gloss or satin, will be easier to clean and maintain.
Applying the Primer and Paint
In most cases the primer and paint should be applied to concrete block with an airless sprayer and back rolled. This is a two-person operation.
Block Fill primer is thick and will require a powerful airless sprayer. A 3/4 gallon per minute sprayer and a 517 spray tip is the minimum required. Large professional units can be rented. Use a gas powdered sprayer on the exterior for added power and convenience.
The roller cover needs to be a thick nap and of the highest quality. Cheap synthetic roller covers become compressed easily and will be frustrating to work with. 100% lambs wool covers work best. Use 3/4—1 inch for smooth block and 1-1/2 inch on split-face block.
Apply a thick even coat and immediately use the roller to push the primer and finish paint into the pores of the concrete block. The goal is to produce a surface that is completely filled and sealed against moisture. This procedure works equally well on interior block surfaces. Back rolling is a great way to produce a better looking result even without the need for primer.
Spraying isn’t always necessary, standard brush and rolling techniques can be used. Dipping and rolling will be slower and more labor intensive, but when painting the interior of occupied block buildings and homes rolling can be the best application method.
191 Responses
If you are going to put concrete sealer on it, do you suggest pressure washing beforehand? Or is there a different prep method for that? I assumed that it would be similar to the process of preparing to paint, but now I’m not sure.
//www.enduracoat.net/Concrete-Sealers/b/2476102011
A good washing and etching is a good way to prep a concrete floor. Vertical walls need just a good washing. Consult with the sealer manufacture for specific recommendations.
It’s been a year since your last comment, so I hope you’re still around.
I’m trying to paint an interior bathroom of an old house. The walls are Ocala block. They have a thin layer of white paint which was done at least 15 years ago. I don’t know what kind of paint was used. It could have been latex or oil. What paint should I use on top of it?
When in doubt use a primer. Since you don’t know the type of paint last use the first thing to do is prime the block. A good oil base primer, like Zinsser Cover Stain, or a good acrylic primer like 123 or Gripper will allow you to use any paint you want. In this cane a good interior acrylic satin or semi-gloss will work well.
When painting a newly built exterior cinder block wall, how long do you have to wait to paint?
You can prime and paint immediately. Concrete block is “pre-cured” before install and using a masonry primer will neutralize the mortar.
What is best to use on cinder block classroom walls? I’ll be painting over existing “Diver Wgote” paint. Would I be able to use a paint with a primer in it?
*Dover White is the color…
Any good quality paint will work without major priming or prep work, assuming the walls and existing paint is in good shape. Maybe something with a good sheen to help with cleaning.
Getting ready to repaint interior cinderblock walls that currently have a semi gloss finish. How is the best way to prep for a new color coat? Do I need to prime before putting on a new color? Sanding the block walls seems like it wouldn’t work.
Any good quality acrylic paint will work just fine without sanding. The sheen isn’t a problem. Make sure the walls are clean before starting the painting.
My interior fireplace is made of split face concrete block and it’s never been painted. Is it necessary to use a primer? I was hoping to whitewash it with diluted paint for a more textured finish. (As opposed to the glossy finish that paint has.)
Thanks!
In this case priming isn’t needed. You can use either a traditional lime wash or a thinned masonry stain. The masonry stain will be a longer lasting product. Make sure to clean the surface well, no dust or soot.
I have a CBS home the home has settle and theres a few cracks is there a paint that can cover the settleing cracks without noticeing it.
If the cracks are small (tight) an elstomeric coating could fill and cover these cracks. But, large stress cracks will need repair before any paint can be applied.
For an existing block wall with peeling chipped paint, should I be concerned about trapping moisture in the block wall if I prime with acrylic block filler and elastomeric paint (seal)? I have read on other websites block walls should breathe.
The block walls will still breath with the block-fill and elastomeric applied. Both of these allow water vapor out but block new water from entering. Block and other masonry surfaces is exactly what it is designed for.
New concrete block, filled with grout. How long to wait before painting ?
wait a couple weeks before applying acrylic blockfill primer, recommended before any paint is applied.
Do I use semi gloss on cinder block walls? What’s best to use especially with having to hang posters with tape on the wall in a few weeks?
Semi-gloss will be fine, but the sheen could also be satin. The most important consideration is the quality of the paint. A semi-gloss will be more resistant to cleaning chemicals and higher humidity compared to other sheens.
We have to reseal basement cinderblock. Currently the sealer/paint is peeling in spots due to past water infiltration. First off, should I be concerned about lead paint; and second, do I need to prime the wall after I chip off the remaining paint before I put on the block sealer?
Lead paint was used in older homes before the mid-1970’s or so. If your home is older than this testing the existing paint is a good idea. Test kits are cheap and available at your local paint store.
Priming depends on the sealer used and the condition of the block. If there is persistent moisture you should use a water blocking sealer that can take hydrostatic pressure before painting. This is done where it is needed only. All raw unpainted areas should be primer, spot primed, with an acrylic universal primer such as Zinsser 123 or Gripper.
I’m working on exterior cinder block wall with smooth surface, paint is peeling. I get confused about when to do my caulking, before or after I apply Drilock sealant / primer??? Main reason I’m needing input, is because the paint around my fairly new vinyl windows, has completely peeled off to the window caulking, leaving gaps for water leaks. Don’t know how to address it? Shouldn’t window caulking have been done differently, not attached to loose paint?
Normally prime first then caulk, but it can be done before the caulking. Paint peeling off caulking is a compatibility issue. Paint won’t stick to silicone caulk and most polyurethane caulkings. Silicone isn’t paintable and there is no primer that will stick to it. Polyurethane caulkings must be primed before painting, oil base primer. No caulking should be applied to loose paint, all loose must be removed before caulking.
At this point remove all loose paint and caulking, recaulk were needed then prime. If you have silicone caulking around the windows then you need to remove as much as possible, if possible, then apply new paintable caulking over it.
The caulking around the window, rather the caulking on the side of the window, looks good & is stuck well, it’s a very good 50 year caulking. It’s the other side of the caulking, where it is supposed to be attached to the paint on my block wall, that I’m concerned about. Are you saying I still should remove all the caulking, and prime it & seal it, and then recaulk my window? I never expected to do all this, of course it is only 2 windows.
Now I’m getting a little worried, b/c after I finish my block wall, I had plans to paint the rest of my house, and I hadn’t thought /or planned on having to recaulk the rest of my windows. I have a total of 23 windows. If fact, I was waiting for my window installer to call me in regards to capping my facia boards & installing a vinyl soffit for me. Since his company installed my windows, I might just ask him to redo all the window caulking properly. It just ticks me off when people take shortcuts b/c they don’t want to do quality work.
I had a stroke a few years back, just before my windows were installed. I have problems with my memory, thought process, words, thinking, etc. I get easily confused about anything, my understanding of what I hear or read is often inaccurate, but I persevere, don’t want no potty, but do like others to be patient & I guess tolerable of me.
I really do appreciate your help and support, but still s/w unsure of how to approach my task. When I’m given too much info, I often get overwhelmed and just lost. Let me think some more about your reply & maybe I’ll understand more about what I need to do.
Again, Thanks,
Lee
Only need to remove caulking if there is a problem, such as dealing with non-paintable caulking or it is loose. If the caulking is paintable and fully adhered then nothing needs to be done.
If the window installers used silicone caulking then I would have them fix it, if possible. This isn’t easy as cutting silicone caulking is all around hard, time consuming work.
An alternative is to apply a very good paintable caulking over the silicone.
Thank you so much for your help. Regarding my 2 windows in my block wall, are you saying if it’s a good acrylic caulking & is stuck good to my window, which it is, to leave it & just apply more of the same caulking? Sorry, I just get things twisted in my mind often. And if I do the above, do I caulk it before I prime & seal the block, or after. My mind tells me to do it before b/c it’s better for it to be adhered to the cement around the window instead of having it stuck again to paint, b/c paint is not as tough a surface as cement. I can send a pic if it would help.
I’ve already pressure washed w/just water, scraped with wire brush & scraper. Was going to caulk some hairline cracks, but I just remembered you said to do that after putting on my Drylock (primer & sealer). I guess I may have just answered my question above. I hope I’m not too annoying & thanks again for your assistance.
Lee
Correct, if the caulking is in good shape and paintable then only apply new caulking were needed. Go ahead an caulk everything in before the primer, this is fine.
The only difference with what I outlined is I prefer to caulk in everything after the primer, often I’m dealing with a degraded substrate and need to stabilize it before caulking. With that said, sounds like you are have a good understanding your needs and doing everything correctly and in proper order.
Thanks so much for your help, it makes me feel much better about what I’m doing. I was planning on caulking tomorrow, but it’s calling for rain the next few days, so I’ll probably wait. I think I need to rinse off my wall too, b/c of all the scraping, then allow for it to dry.
If you have time, I do have another quick question. I have a wooden deck attached the block wall . Do I need to take down the decks post, so I can paint the wall behind them, or just paint as much as I can with them in place? I think there are only 2 bolts holding each post in place. I’m sure the deck itself has bolts holding it in place, but figured that would be too much of a job, plus it’s not necessary to detach them & paint. I did notice that the block wall beneath the deck is painted, so I guess I’ll have to crawl under the deck & paint that part of the wall too. I had a hot tub removed from center of the deck, so it shouldn’t be too hard to crawl under it.
Thanks again for your help.
Lee
No need to remove the deck posts, just paint whatever you can reach. Same goes for under the deck, a pain but if it is visible then it should be painted.
Thanks so much. This is my very last question, I promise, with my fingers somewhat crossed. Should I even attempt to spray a sealant or something underneath the deck, or just not worry about it? I guess you’ve already figured out that I’m a little detailed oriented, but it my be seen as obsessive compulsive. I really am thankful for all your help, this is a great resource site, and I appreciate you willing to assist & share your knowledge & expertise.
Thanks,
Lee
The exposed concrete block under the deck – if it is visible then is should be painted the esthetically match the rest of the house. If it is hard to reach and not all that visible then I wouldn’t do it. Your call.
The exposed deck frame – no, this should never be sealed. Sealing the deck frame will accelerate rot by trapping moisture in the wood. No paint or even deck stain.
Help, Help, Help!!! We have a block house built 1978. When we bought it the white paint was chalky and we painted over it. When it started peeling, pressure washed off just those couple areas and painted again. Now, you guessed it, happening again in more areas. This is a huge house and it’s breaking u$ ! My husband started pressure washing with the intent of taking ALL paint off down to chalky white, but wow! After hours he’s hardly touched on the total job. Is there a paint that would ‘glue’ the peeling down where it’s easily pressure washed off and hold the paint where it’s not? Maybe oil-based Zinsser? If so, could we tint it and not top coat it for a while? This house was once a commercial building and takes about 27 gallons. ;/
At this point I would powerwash, remove only what will come off easily, spot prime then paint (either paint everything or paint only the spots where it is primed. If you think this will come back elsewhere in the near future then spot priming and spot painting is a better bet.
There isn’t a primer that can penetrate through paint and glue it down, wish there was. The only primer that can glue down edges is Peel Stop, used on old homes that have old cracked paint. I don’t think this would be useful in your situation. A good primer to use for chalky surfaces is Zinsser 123. The acrylic primers do a better job binding with any remaining ‘chalkyness’, do make sure to wash well and try to remove as much chalk as possible from the surface before priming.
Zinsser 123 is tintable to a point but should be painted over within a month, can get really hard after a while and might have problems with paint sticking, producing even more peeling. Best to paint over all primers with in a week or so.
Thank you for your reply. Are you referring to Acrylic Zinsser? Not oil based?
Correct, Zinsser 123 is acrylic.
Thanks. I did have a painter come out, finally and recommended Holzer primer. I am thinking Zinsser bc of the availability/price. Let me know if you think Holzer is far superior.
I never heard of it, might something more regional. There’s always better primers, STIX by Insl-X is really good but expensive. The Zinsser 123 is a good primer that adheres well to difficult surfaces, is readily available and reasonably priced.
Do you need to wait to paint a cinder block wall that has been core filled every 4 feet. The mortar still looks wet where the wall has been core filled. We repaired an outside wall and are anxious to put the house back together before school starts as it is a bedroom. Thanks
I would wait for a few days, maybe 5-7 days, for excess moisture to leave then prime and paint as usual. Summer heat and lower humidity can speed up this time. One way to check if excess moisture exists is to take some plastic sheeting and tape, seal it to the wall. If a lot of water droplets form under the plastic then wait a bit. Some moisture isn’t a problem but a lot can cause bubbling and peeling.
Thank you!!!!!!
I have painted my basement with 3 coats of Sherwin Williams Luxon Concrete block primer and sealer and a finish coat. I just realized that the concrete block which is sealed from the outside as well, now has no way to breathe due to being sealed on both sides…
Would you recommend removing the paint somehow so I don’t cause any damage to the concrete block? Are there any visual cues to show if the block is now retaining moisture (pulling from the ground i’m assuming)?
The Loxon does allow water vapor to pass through, so the wall will breath a little. The number 1 thing to do mow is make sure the dirt around your home slopes away and there is good drainage. Signs of excessive water will be staining and bubbling of the finish coat. Mold along the edge, especially with carpet, is also an indication of problems.
No need to do anything with the block wall but do double check the landscaping.
I used Zinsser block filler on my bare basement blocks. Can I put a sealer over it? Such as Watertite?
Yes, you can put any top coat desired over the block filler. The Watertite will work well.
Thank you very much.
Hi,
I was about to paint my garage wall (which is below ground) but upon miving everything away from the wall there was some mold in certain areas. I used white vinegar to remove the mold and then did a full wipe down with water. The wall was previously painted and spot patched for cracks by previous owner.
Upon inspection, I had some efforescence that I removed with a wire brush and spot patched cracks with UGL Drylok Fast Plug Hydraulic cement.
I think I am now ready to paint and wanted to know if using an elastomeric paint would be a good choice? I don’t know if what is on the wall is a block sealant or plain old paint? Or would a product like Sherwin Williams Loxon be a good choice?
What would you recommend?
Thanks in advance!
LC
Use Drylok Masonry Waterproofer as a base for your final paint. Will work much better than an elastomeric coating or Loxon, both are best used outside and above ground.
Thanks for the quick reply. It is very much appreciated. This is a great site with excellent information!
Hi, I have a couple of follow-up questions.
Should I or can I do 2 coats of the Dry-Lok Masonry Waterproofer? And
Do I have to apply the product using a thick roller and back brush it? Is the best approach?
Thanks again,
LC
You can do 2 coats instead of one very thick one. Personally, I would use a 1/2 or maybe 3/4 inch roller. Work the material well but don’t over work it, you will know when that happens. Also finish each roller stroke in the down motion, this will lay down the roller stipple in the same direction across the wall making a better look.
Oh, you don’t have to back brush but you want to fill in the open pores of the block. A roller will do this just fine.
Great, I had purchased a 3/4 inch roller for the job. Thank you! LC
Hello! My project is preparing new 16” concrete blocks which will sit outside in a wet climate and perform the function of providing weight and support for the legs of an outdoor canopy at the entrance of our residence. These will not be subject to foot traffic, but they may get stood upon occasionally. They will also be subject to sun exposure when it is not raining
Above all, I want to be able to clean the blocks periodically with light pressure-watching (to remove the inevitable mold, moss, and algae). Originally I was planning to paint the blocks a color, but now I am not sure that would be a good choice – whether paint would be permanent enough or easily renewable with good appearance.
I thought this would be an easy project, but I am running into a limitation of several of the usual materials which are not permitted for sale here in Hawaii (due to regulation?). I wanted to use a satin, self-priming masonry paint, but here it is only available in the flat, and I can not get the satin shipped here, either. The flat version is not good from a cleaning standpoint. Block-fill primer is apparently also taboo … and other products.
A few questions …
Does a new (porous) concrete block need etching?
Since there is no mortar, do I need to use a masonry primer?
Would priming and top-coating with a good-quality acrylic paint work well with concrete block? Would a concrete “conditioner” prior to painting be effective?
If I forget about color and just go with sealer … which one?
One vendor suggested using a colored stain and top-coating with a sealer which would finish-out glossy (and hence be cleanable). I’m wondering whether the sealer will hold up to cleaning, whether it will yellow from exposure, and how renewing it (if necessary) will look. I also would prefer a satin or semi-gloss finish.
I’m not concerned with an uneven concrete surface in terms of appearance, but it may foster mold growth if it is not thoroughly sealed.
Help!
#1 Etching isn’t needed. The block if fully cured and has a stable PH and open pores.
#2 If you apply a paint you really should prime. A general purpose exterior acrylic primer will work well. Every paint store will have an exterior acrylic primer.
#3 Paint will work reasonably well but will require periodic maintenance, remove loose paint and primer before painting. If primed, no conditioner is needed.
#4 A straight clear sealer will work well and easy to maintain. Wash, dry and reapply, in most cases. I recommend Seal Krete concrete sealer or something like it. 100% acrylic.
#5 I would apply a masonry stain (semi-transparent) and top coat or seal it with Seal Krete or something similar. Overall this is the easiest to apply, easiest to maintain and cheapest way to go and have some color.
Staining and sealing should do well with cleaning (low psi) and weather. Some maintenance every 2-3 years. Paint could go 5-6 years but could become a nightmare with heavy prep before repainting. Paint will peel since the block isn’t fully sealed with mortar. Without mortar the top and bottom edges are exposed to water.
Staining and sealing can be done with a garden sprayer, if it has a good spray fan. Sealing each block before assembly would be preferred.
Thank you for taking the time to answer questions. It’s a great help and have learned a lot. We replaced windows and we now have fresh, unpainted stucco around the windows. I bought Seal Krete to waterproof the stucco but the label says do not use if the temp drops below 50 degrees in 24 hours. Its been getting down in the mid 40’s at night so I decided to use Zinsser 123 since it doesn’t have the 24-hour requirement. Can I later paint over the 123 with Seal Krete when the temp gets warmer? Also, I was going to repaint the house in spring but u suggested the 123 will harden. Should I just paint over it now with an acrylic or latex paint and then repaint it when we paint the whole house?
You can apply Seal Krete right over the primer but it would be easier to just apply a coat or 2 of paint instead. Plus paint will do a better overall job.
Hi there!
I travel for festivals and use deck blocks to weigh my canopy down at windy events or when I can’t use tent stakes.
These blocks are very crumbly and leave concrete dust all over the interior of my vehicle.
Is there a way to seal these blocks so that I can carry them around without getting chips and dust absolutely everywhere? They don’t need to be ultra beautiful – just functional. I am a face painter, so whatever I use needs to be latex-free since I touch strangers’ faces all day.
Thanks!
Any clear concrete sealer will do the trick. These sealer, like Seal-Krete, are acrylic not latex so that won’t be a problem. Apply to all surfaces, inside and out several coats, until saturated with sealer.
An alternative is house paint. Any descent paint will do but priming will still be needed. With paint the “sealer” is tougher than a clear coat and easier to maintain.
I have the cinder block basement walls sealed professionally three years ago. I’m not sure what product was used but understand that it was from a professional – commercial line. I’d now like to paint them.
Do I need to prime the walls first? What primer would you recommend? And what finish coat paint would you recommend? I’m looking for a semi gloss finish.
Do I understand that I should NOT use elastomeric paint on the interior walls? My main concern is painting without damaging or weakening the prior sealing process. Thank you in advance.
P.S. I can’t imagine any builder using cinder block for basement walls. House was built in 1966. 🙁
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Using a primer is a good idea, better safe than sorry. A standard acrylic bonding primer should work well; Zinsser 123 or Insl-X Stix will work well. The finish paint can be any color sheen you desire. Do not use an Elastomeric coating.
Hi i am about to paint the exterior of my block home I have pressure washed I’m just wondering how long I need to wait until I can paint after pressure washing?
Overnight will work. The block needs a little time to dry out before painting.
Thank you for the great article! We are building a privacy fence using cinder blocks for the posts. The homeowner wants a stucco finish but stucco is unavailable in our area. Can we add sand to the primer or paint to achieve the desired effect?
Sand added to the primer won’t look like stucco. A sanded elastomeric paint might work if available. Another option is a basic stucco patch, powder available at hardware stores. Or use your mortar mix, add extra portland cement and lime. You will need to play with the mix to get something that will stick and look good without cracking.
Another question, there is only 1/8 of extra space for paint. Will we have to take down the columns and start over or is there a way to fit the primer and paint in that space?
I don’t understand. What is this space?
I asked a paint supplier do i need a primer before i paint my exterior wall which is a large area he said no just 2 coats on and it be ok dont know what to primer or not thanks
Depends on what the original paint is and the shape or condition of the original paint. General rule is a primer is needed when changing types of paint (oil to latex), seal a porous surface or seal stains.
Great article! I am preparing to repaint my 1955 block house. It has been repainted a number of times and layers are peeling off. With a pressure wash and assuming not all of the existing paint has come off, when I paint a new coat will the texture of the on-and-off original paint show through?
It will show. One way to lessen the look is to sand back or feather the edges of the peeling areas. This will help.
I’m painting exterior smooth concrete block barriers to my yard. When I water my yard water leaks into my driveway through the cracks in the walls. What should I fill these cracks with before painting? The cracks are bigger than a hair line crack and are vertically as long as the 2 to 3 ft wall.
A good caulking will work well. The biggest problem you will have is paint bubbling from water coming through the walls. Could try priming with Drylok masonry primer then painting.
I have a cinder block basement built in 1991, and to avoid drywall wanted to paint and seal for moisture. It’s never been painted, and there is some efflorescence. My concern is prep, as the basement’s pretty full and will need to do in stages. Can I just dry brush and vacuum all loose debris, or do I need some other chemical and let dry? What are your thoughts on Loxon primer, maybe even the combined primer and topcoat version. Or, should I use some other brand for best adherence longevity?
Yes, vacuuming is fine. The efflorescence will need some washing, white vinegar, no-rinse TSP and warm water will work for most deposits.
A really good foundation primer, below grade, is Drylok. It can be painted over with any paint you choose. Drylok can stop moisture from coming through the wall and bubbling your paint.
I’m looking to paint the cinder block walls in the basement of our 1959 house. The basement has never been painted before. There was previously an issue with water seeping up from the floors… It’s been taken care of with an interior french drain and sump pump system –there’s been no water since that was installed over a year ago. Other than cleaning, what should I do to prep for painting? Primer? Sealer? Something else?
After cleaning and repairs, if needed, a good primer must be applied. You have several choices but if water seeping isn’t an issue then a good universal acrylic primer will work. Zinsser 123 or equivalent. For a better seal use Drylok as a primer.
I am preparing to repaint exterior of my 1945 block house. It has been repainted a number of times and layers are not peeling, its in good shape. I just don’t know what paint to by at Lowes. My husband said latex would be ok, but I am afraid that it will peel as it did on the interior bedroom wall. Trying to do it as cheaply as possible as I have many other projects going.
100% acrylic paints are the standard now days and most likely all that is available at Lowe’s. A high quality acrylic exterior paint will stick well to a clean surface. I don’t know their products but buy the best you can afford.
I am painting over previously painted block foundation in the basement. The bottom two feet of the block have efflorescence and the paint is bubbled but there are also areas where the block is actually crumbling. I added a washer/dryer in there 4 years ago and I moved it today to prep for repainting and found same thing on the ground, bubbled paint and crumbled concrete. I have removed all loose paint and scraped with wire brush. I have etched all exposed concrete with Muriatic acid. I was planning on spot priming with zinsser 123 and then painting entire basement walls and floors. Is there something else I should be doing? Should I be using drylock instead of primer? What should i do about the crumbling concrete?
Drylok is a great primer that can help stabilize masonry surfaces. At this point it would be a good idea to spend a little extra and apply Dryloc. Also, look to the cause of water infiltration of your basement walls. Landscaping, such as inadequate drainage, or a leaking gutter can cause big problems.
First I’d like to say this page has been a fantastic resource, thank you! I’m attempting to repaint the bathrooms at the shop where I work. I have no idea how old they are, but the paint is thick & has crackled/chipped in various places. As I scraped it off there is a chalky green residue between the block & old paint. I tried scrubbing it off with a wire brush but that didn’t seem to do much, also the mortar is very crumbly so brushing that is pretty sketchy…
My boss doesn’t want me to spend a ton of time or money on it but I’m sure he doesn’t want it peeling & chipping either. They are above ground interior walls but it’s very humid & sometimes rain blows through the roll-up door into one of them, so moisture can be a problem.
What would you recommend in this scenario?
First carefully scrape any loose paint, wash if needed (no-rinse TSP works good). Now apply a primer, Zinsser 123 or Kilz acrylic. The primer will help with the loose mortar, gluing it together. At this point you can do some patching or go ahead and paint. Use a semi-gloss paint to help with the moisture.
Wonderful site, Thank you! I am about to paint my cinder block 2 story garage exterior. It’s been painted before. Every paint store tells me something different! I’ll pressure wash, let dry. One side is shaded all the time and built into a hill, seems damp inside. Problem for another day!
Was told a latex without primer would work. You seem to recommend Acrylic? Hope to use a regular paint due to cost, as opposed to a specialty type. Thoughts?
Thank you!
Acrylic and latex are the same thing now days. I don’t think a real latex paint is manufactured anymore.
You can use a regular paint. The biggest thing with cinder blocks is their pores, lots of them. Make sure to use enough paint and work it well to fill these pores.
Does the cement block exterior wall need to be dry to paint? We have pressure washed it and it has rained every day since. Thanks.
Depends on the type of paint being used. For block fill primer and an elastomeric coating, damp block is OK. For a regular house paint the block needs to be dry.
Is there an optimal temperature to paint blocks or do high temps affect painting?
High temperatures do affect painting, including concrete blocks. The primer (block fill) and paint dry too fast, not penetrating or sealing well plus all around looking bad. Typically lower temps are best, around mid-70s-80, but misting with water can help at high temps. Misting works best with acrylic block fill primer and elastomeric coatings, test with other materials for bubbling during drying.
I have a recently constructed cmu shop and just finished aggressively pressure washing the interior walls for paint. I plan to use an epoxy primer, 50% solids that claims can be applied 8 mils thick. I don’t think normal calculations for paint coverage apply due to the porosity in the block. How do I estimate paint consumption? Block is density is 105 pounds per cubic foot (very porous) and is very common here in Florida.
Pre-fill the pores with a block-fill primer, standard acrylic will work for most circumstances. This will give you more predictable coverage for the epoxy. Use the manufactures recommended coverage, on the can or msds. Add 20% to the materials total for spraying and surface texture.
Hi, first of all I am impressed with the site content and you taking time and answering questions! I have hopefully a quick question – I have removed old stucco or alike (looked awful so I could not resist) and I am down to some of old paint and original cinder block from 1950s. Will power wash and I would like to paint it. However in a year or so I would like to add some texture (textured concrete or alike) or culture stone or stone. I would like to make sure that paint will not cause that nothing will stick to the wall later? Is it safe to seal and paint if planning to add something on the top of this in a 1-2 years? Thank you!
I think adding the stone will be fine. You can always attached some expanded metal lath with concrete screws to help with adhesion.
But adding a texture could be problematic. It would be best to apply the texture (new stucco finish coat or ??) first then prime and paint. For the stucco repair use a efis base coat and acrylic top coat for the texture. You might need to look for a local stucco supplier for the materials or use Rapid Set Motor Mix or Cement All for the base repair and possibly the texture coat as well depending on the look your after. Be warned these materials set up very fast, you might need to use Set Control to give you some extra working time. All of these materials are available at Home Depot.
Hope this helps.
Hi – have a couple of homes in sunny hot Arizona needing painted
Want to know best process to get this one home repainted. I’m getting older and just want it to last ‘forever’ and not have any issues. Home is cement block painted with latex, the wood trim, sides and patio – repainted years back with oil base paint with extra linseed oil added and it soaked up a couple of coats then painted over with latex (HD Behr high gloss white lasted about 15+ years – now it’s peeling and looks really bad on the south and west sides of home, maybe have some wood rot, the block has a chalky feel when you run your fingers along it. Original wood was all that super dark brown color from the 70’s. The super white really helped lower electric bills in summer so thinking lighter color, not necessarily white again, just haven’t decided on paint brand, would like semi-gloss on exterior and high-gloss on doors/garage door. Advice appreciated
The process is straight forward;
At this point paint proceeds as normal. Choosing a good quality paint and applying 2 coats on everything will help. I like brushing and rolling whenever possible to push the primer and paint into surface pores.
Lighter colors with a good sheen is a good idea. You can always add color as an accent; shutters or front window trim or corner trim or front door and/or garage door(s) can be used as accents.
Hello! Thank you so much for providing such valuable information, and taking the time to answer questions. We installed decorative concrete block (breeze block) in our carport in Seattle a year ago. We are finally getting around to painting it. I scraped off all loose concrete and power washed it today. My understanding from your article is we should use an acrylic block primer and we will need to use your roller and brush technique because we don’t own a sprayer.
Any other tips for us? We are using a lovely dark grey masonry paint from Farrow and Ball. It was pricy so we are hoping to get it right the first time ; )
Sound like you already know what your doing. Correct, use acrylic block fill primer to seal up the block. Work the primer as well as you can into the pores, if needed apply 2 coats. If you don’t fill the pores now you would wind up using 3x more paint, an expensive prospect. And be mindful of the weather.
I am attempting to paint some concrete walls in the basement of our 1965 home. The wall has been painted by the previous 0wners, but I’m looking to apply a new color. I am using a Glidden latex interior paint for a top coat. I have attempted applying this Glidden paint directly over the previously painted wall, as well as used a Drylok waterproofer and BIN shellac based primer. Each time I put the Glidden paint on, it bubbles and will not stick to the wall or primers. Any suggestions on how to get the paint to stick?
Well, use a better paint. Glidden really isn’t that good. Sherwin Williams ProMar 200 or better. You try another primer, Zinsser 123 acrylic.
The bubbling is a bit perplexing; even cheap paint should go on without bubbling. Something is coming threw the primers, moisture maybe?? The sticking problem is the paint, need to use a better paint.
I love this site! I don’t have any questions because the answers are already here. We have repainted our 1959 Florida concrete block house with great success! We washed, we peeled, we sealed, and we painted. We had a new concrete block addition as well as stuff that had not been touched in 20 years of Florida sun. It looks new and wonderful and we saved thousands of dollars doing it ourselves. Thank you for all of your helpful information.
I’m painting a block wall house that is in good condition. No peeling , no mold and very few cracks to patch. Can I wash it with a hose and stiff pole brush or do I need to pressure wash it . If I use a quality paint will my paint job last . Please give me your advice on how to do the job
A pressure washer is faster and can do a good job but since you don’t have any major problem areas manual washing will be fine. Make sure to rinse well if soaps are used. Using a good quality paint is a must in all situations and helps provide lasting good results. Second to quality paint is quality caulking. Make sure to seal around windows, doors and all wall protrusions with the best caulking you can afford.
I want to paint a newer block wall that separates my neighbor and I. It’s about 50 ft long and has not been painted or treated before. On their side they have a low planter about 2′ deep with bamboo that they water regularly. I live in a dry climate in southern california. I was hoping to skip the priming/sealer step and do 1 coat of paint. It seems most comments and directions here are for basements or walls that are part of a home where I can see needing to be sealed from moisture. This is a fence and I don’t know if the primer is necessary or not. What do you recommend? Thanks!
Moisture transferring through the block could be a problem with using paint. A masonry stain will be a better choice, solid color acrylic masonry stain.
I have a mural painted on an exterior cinder block wall and want to protect it. It was primed and then painted with acrylic paint. What can I put on it to help preserve it and not dull the colors?
Seal-Krete masonry sealer would work well or any exterior grade acrylic clear-coat will work, could even use a varnish or poly.
I recently bought a 1980’s cabin basement that has rough cinderblock surface, never painted. The cabin has had a mouse problem and we have been eliminating them, but do to the infestation, there are actually trails along the block at the top of the walls where these dirty little things travelled over the years. We have been cleaning them with bleach water with some success, but some areas are very stubborn. What would you recommend for cleaning?
Also, would you recommend painting/sealing these areas? We have also had a moisture problem in the basement, so is there a sealer that could help with both issues?
Thanks!
TSP, hot water and a scrub will be your best cleaning option. Make sure to rinse well. For the primer use Drylok, or similar, on the moisture problem areas. For other areas a standard acrylic primer, like Zinsser 123, will work well. If you have stains coming through the primer spot prime or seal the stains with either Zinsser Cover Stain or a shellac primer.
Thank you for all your incredible guidance! I have 3 questions:
1) Our community has slub block walls just like on the below website and we’d like to know if we can have them painted in a durable and low maintenance way?
https://www.paclandinc.com/portfolio/culver-city-90232-cmu-slump-block-wall/
2) We had some sidewalks repaved and there is concrete overspray all over the surrounding natural brick raised planters. Is there a way to remove this ugly grey residue from the red brick? Powerwashing doesn’t seem to do the trick
3) We have a ton of red curbs that needn’t be red! We’d like to bring them back to natural grey. Can you advise on how best to remove the red paint? Or are we stuck with trying to paint over the chipping red areas in grey?
Thank you!
1) Yes, the block walls can be painted. This would be the same as any masonry surface. You have a choice as to the finish; Use a primer then paint (regular paint or elastomeric coating) or use a masonry stain. There will be periodic maintenance as all stains or coatings will need to be refreshed time from time. But, with proper prep and choice of a high quality materials maintaining the walls shouldn’t be a problem.
2) Not sure. You might have to use a mild acid and wire brush to remove the residue. Who ever put it there should clean it up.
3) The paint could be removed with abrasive blasting. Soda blasting might be a good option. Contact a contractor that has this equipment. The only other option is to scrape and paint.
Hello, I have a a 50×40 block building with 16 foot tall walls. It is older, probably dates to the fifties. We have had an ongoing water problem when it rains seems to be always on the west facing part of the building. We have cauled, painted redid a great product on the roof (flat) but it is still having a water issue. We considered stuccoing it but our smart guy has suggested we do an Elastomeric coating. We thought we would do that on the west side 50×16 face and paint the north and south sides with regular paint. The paint is not peeling noticeably anywhere. The paint contractor is going to power wash scrape and then caulk and do 2 coats of the Elastomeric coating in the way we have read to do it, spray back roll cure between coats. My concern is that if the paint does not come off with the power wash will we be able to get good mechanical adhesion on the clean painted block? I have the equipment to go out and sandblast the block but my partner feels the sandblasting will be to aggressive and wear out the old blocks and create a worse problem. And he could be right. . The goal is to get a seal on the long term blocks so moisture does not make its way through and disturb the tenants offices with leaking. Please advise with your experience and wisdom. Thank you.
The elastomeric should stick well over the old paint but the old paint can be primer to make sure there is good adhesion. Sandblasting is an option as long as no damage occurs. Priming is an easier alternative that will provide the increased bond you desire.
I have 67 feet of an exterior 40 year old cinder block wall on my property. It has concrete stain, oil-based paint, then acrylic paint (in that order.) I am assuming the last paint was acrylic because that is most of what is peeling away from the white oil-based underneath. However, some of the white oil-based has peeled off also to reveal the old dark green concrete stain. I am assuming this is because the concrete was never sealed or primed. I scraped all that would come off, had any loose mortar repaired and cracks filled, and now I must paint. It looks awful, it is the first week of September in Michigan, I work and I am not a young gal anymore. I would like to try and paint it myself with the very best products available so that I wont have to do it again for a long time. What kind of block filler should I use to cover this mess, and what kind of elastomeric paint would take a neutral color and last the longest? Thank you so much
Prime the wall first with a good universal primer, like Zinsser 123 or equivalent. This will help get the new paint to stick and fill some pores. If needed use an acrylic block filler over the primer but you could just apply 1 or 2 heavy coats of elastomeric, Sherwin Williams Sherlastic is good and inexpensive as well. If you roll it on you should be able to fill most pores. A lot of work for sure but it will last.
Very helpful website. Thanks.
I have a 1950s CMU garage. I’m not sure if it has been painted since it was built. I assume it has lead paint, but it seems very intact. I assume there’s no problem painting over it.
I just had waterproofing done with some sort of rubber membrane. It goes up about 15 inches on the walls (interior) and my contractor says it can be painted over with no problems.
I’ve already pressure washed the walls with just water. That removed a lot of dirt. Do I also need to wash them with TSP or anything else?
Before calling the waterproofer, I painted an by 8’ x 14’ back room with dry lock after grinding out and filling seam between floor and block with hydraulic cement. When it still leaked I called the waterproofer.
I still need to paint the main 14 x 22 garage section. There are a few sections of unpainted CMU where some shelving units had been installed. I plan to use the remaining dry lock as a block filler for those sections.
Now the questions: Should I prime the whole thing? Should I prime it with block filler? Should I put a finish coat over the dry lock in the back room or will that work fine as a finish coat? (One of your posts suggested using a satin or semi gloss finish for easier cleaning.) The waterproofing contractor filled some cracks and holes in the block with polyurethane caulk. One of your posts said polyurethane caulk needs to be primed. What do I prime it with?
Thank you very much for your assistance.
Cleaning with TSP isn’t needed if the surfaces are clean. Prime the whole thing with an oil based primer, like Zinsser Cover Stain. This will produce a good foundation for the new paint. The poly caulk needs priming with the same oil based primer prior to painting. The dry lock can be painted over if wanted. Shinier paints are easier to clean but flat is fine if this is your preference.
I have new foundation split face block walls that I am going to paint. We are along a creek and in a flood zone and it will flood at some point. I’m not trying to keep “flood water” out, I’m just trying to keep moisture out. Do I seal the interior or do I seal the exterior? Or both? I was planning to buy SW Loxon Concrete Masonry Primer & Sealer and topcot with SW Resilience Exterior Acrylic Laytex paint. Also, I don’t want to lose the look of the split face block. I am also not opposed to other brands. I would love to use an airless paint sprayer too if I can find one that the primer will work with. Thanks for in advance for your advice!
You want to seal the foundation from the outside if possible. Damage to the cement foundation could happen if moisture is trapped in the walls. Possible french drain with sump pump could also help, if applicable. Paint and primer, such as Loxon and Resilience, are above ground only.
Do I really need an oil based primer? Also, if I’m using a block filler, do I need to prime first, then block filler, then topcoat? I thought black filler was a primer. Thank you.
Block fill doesn’t stick well to previous coatings, like old oil based paint. Since the current paint, modern acrylic or latex, peeled a better primer is needed to make sure the new paint sticks and not peel in the future. You probably won’t need the block filler after priming with the oil based primer as this will fill a lot of pores. Choosing a thicker paint, like an elastomeric coating will also help fill the pores.
I am in the process of finishing my garage walls and inside garage foundation blocks. I am preparing to install a resistance pool in the 3rd garage space and want the area to be as waterproof as possible. My house is 3yrs old and I recently added moisture proof drywall over the lower 6’ of the original drywall. The foundation blocks inside the garage are approximately 10” high and have never been painted. I realize that I will need to clean off any drywall patching mud and paint that has landed on the blocks but it will not be possible for me to wash the area as I have heavy equipment that will be difficult to move at this time. I want to make sure I understand the process for what steps I should take with regard to painting and sealing these indoor/garage foundation blocks
1. Clean any debri off of blocks and vacuum and sweep off before going to the next step
2. Since the blocks in some areas are not smooth, I was going to apply 2 coats of acrylic block fill primer
3. Next, paint 2 coats of satin Sherwin Williams acrylic paint
4. Since the pool will cause moisture and possible water splashing on to the foundation blocks, I was going to add caulk to the area where the painted drywall meets the foundation block and where the foundation block meets the finished epoxy floor. I want it to be sealed as best that it can. What type of caulk would you recommend?
Can you let me know if this sounds like a good plan or is there something I am missing or that you would change? Can you recommend any specific products for the block fill primer?
Sound like a good plan. 1 thing to add is maybe use an epoxy paint on the foundation block, contact your local paint store for availability and pricing. The best caulk is a good urethane, Sherwin Williams Shermax will work well. Any good acrylic block fill primer will work, the most important part is what is put over it.
nice thread. Wish I had a place where I could add pictures.
Older basement 50s, cinder block, Was painted white, with with some areas of Efflorescence. Was scraping the efflor.. and behind that is the bare cmu. However, It’s apparent the block was painted with some drylock overtop a green paint as I can put my 4″ knife behind some of the paint and pull off up 6″ pieces. Some places the paint is adhered well to the block.
So what I’m left with is some bare cmu, some paint, and some concrete patch areas. A little bit of a hodgepodge.
Was thinking, after scraping, washing with stiff brush a Vinegar/ TSP (combo) Not sure of the mixture, just going to improvise, Unless you have a ratio you recommend). Then paint with some primer (just not sure if Oil Based or Water Based would be best). Then painting, but I’ve heard that flat is better for basement walls. Is that true? If I go with the Oil Based Primer, would I need an oil based paint?
As a lot of people commented, thank you for you time. Most excellent thread.
Sorry for the late reply. A couple cups of vinegar per gallon of warm water with a 1/4 cup TSP will do a good job, rinsing will be needed. Could use no-rinse TSP, easier to use and still does a good job. Your local hardware store should have some.
Use an acrylic bonding primer, Zinsser 123. Regular wall paint can be used and any sheen, whatever you prefer. No need to go with flat unless that is your preferred sheen.
My house was built in 1985 and the basement is unfinished with cinder block. The cinder block was painted white by the previous owner (no idea what he used) and could use a touch up after all of these years. The paint is not peeling. It’s just a bit drab, so I’d like to lighten it up. The walls are dry. One small isolated area of the basement floor occasionally gets wet (perhaps 2-3x per year) when the rains are especially heavy, but it doesn’t intrude on the rest of the space. It also doesn’t affect the wall. What type of paint would you recommend and what should I do to prepare the surface before doing so? Do I need to re-prime the surface given the age?
Appreciate any guidance that someone can give.
Most likely regular latex or acrylic house paint was used. Go a head and use a good quality interior paint, sheen your choice. Stains will need priming with a stain blocking primer, shellac or oil based work best. The rest shouldn’t need priming but you can test the original paint by rubbing the paint some alcohol, rubbing or denatured. If it softens then it is a latex (regular) type of paint and no priming is needed.
Hello! We have a 1972 home and I’m going to paint the interior basement cement block walls. Whoever owned the home prior painted them incorrectly and they are chipping and flaking and water has gotten in at some point. No water has been in the home for 20 years. (Sump pump installed with drain tile) The walls are crumbly in some spots and there looks like there may be mold. I have some Kilz Mold and Mildew Primer and the Restoration Primer. Which do I use? Do I use TSP after scraping? What kind of sealer/paint should I use? I would like to seal it for moisture and also paint it. Thank you so much!
First wash everything and kill the mold. Bleach and TSP is the best solution but you can also use bleach with no-rinse TSP substitute or a mild dish soap. Scrape away any loose material then prime. Either primer is fine, depends of the overall condition of your walls. If you have a lot of stains then the restoration primer would be better.
Thanks for responding! Wondering about the paint. Should I use a drylock or regular paint? We have 2 dehumidifiers and a sump pump. No actual water just damp feeling. I bought “Behr Dry Plus- Masonry Waterproofer”. Will that work? Thanks again!
The Behr paint is fine as long as there isn’t water vapor in the block. You can check this by taping a 12×12 inch (or larger) piece of plastic to the block wall and waiting for 24 hours to see if any water droplets develop under the plastic, use duct tape or similar.
If you think there is excessive water vapor in the block wall then use the Dryloc, better product all around.
Note: Best to prevent water from entering the basement walls by sealing the outside foundation and/or installing ‘French’ drains. Trapping water in concrete, block or otherwise, will degrade the walls over time causing all kinds of future damage.
Hi, Thanks for this page. I started prepping a concrete block wall that is part of a semi-finished stairwell outside my house that leads to an unfinished basement (the blocks are below ground). The house is old and the concrete blocks are painted (likely in the past 25 years). I’ve scraped the paint and wire brushed the blocks. Some of the blocks appear to have a light green ?plaster? coating about 1/8″ thick. Some of the plaster chipped out in chunks as I was scraping, and it’s almost sandy underneath. Otherwise, the wall seems to be fairly solid.
My question — I am not sure how much more prepping to do, i.e., sand those chunks down smoother or find some cement-like material to patch the chunks or just leave them as is? It’s not a high visible part of the house, so it doesn’t need to look great, but I do want to do a proper, if amateur, job. I also don’t know what the material is and am hesitant to keep messing with it.
My plan after prepping is to wash the walls with non-rinse TSP, paint with Loxon and then finish with the exterior paint recently used to paint the rest of the house. I live in a fairly wet area — water does sometimes get into the stairwell, though mostly on the stairs, not through the walls.
You’re doing a good job with the prep. Right now just fixed the damaged areas, Cement All from Home Depot works well. No need to sand just patch as best as you can. You can prime with the Loxon the next day then paint after that.
Getting ready to paint basement concrete block walls and looking for some advise on best products/process to use. It has been previously painted and also had water entering through the bottom 2 feet of the walls when we moved in. I have changed the outside grade and landscaping to get water away from the house and I haven’t had water come in for the last 2 years except for heavy rains i will get a wet wall. Also, the previous water penetration has left some mildew stains and efflorescence. In addition, I just finished chiseling away any loose mortar and repointing these joints with new mortar so will have fresh mortar joints to paint as well. I plan to scrape away all loose paint and then will do a wash with TSP. Will Zissner 123 primer and then a good acrylic paint cover the mildew stains and new mortar joints? Or should I go with the drylok masonary waterproffer for this job.
The mildew stains might need an additional treatment with a shellac or oil based stain blocking primer, BIN or Kilz. Go ahead and prime with the dryloc for the walls that occasionally get damp or wet and use 123 everywhere else. This will help stabilize the wall and keep the moisture from becoming a problem in the future. Then wait overnight to see if the stains bleed through. Spot prime the stains then paint.
Hi, I’ve no particular question to ask at the moment, but I’m interested in using block in future, so I’ve been reading many of the questions and answers here. It’s fascinating stuff. This is such a valuable resource, and you deserve a lot of credit for giving your time and expertise in answering. Thank you very much!
We have just built a bessor block fence out front and back. We put bondcrete on it first than we painted it with water based paint. But now when It gets wet the white streaks are coming out of the bricks how can we stop this
I’m not familiar with Bondcrete but from what I read it should have sealed the pores and act like a block fill primer, neutralize the surface ph and ready it for the paint. Water is getting in to the block from somewhere. When you applied the Bondcrete; Did you apply thickly and work well with a thick roller? Getting the pores sealed it very important with block walls. At this point wash off the streaks, garden hose and maybe a little scrubbing with a broom, and apply another coat of paint. Apply a heavy coat of paint with a thick roller and really try to make sure the pores are filled, especially the to of the fence wall. Check for cracks that are not fully sealed and use caulking to seal them up prior to painting.
I cannot find this addressed here or anywhere else.
I want to waterproof inside and outside of a new/never painted concrete block wall in a manner such that afterward, I can paint one side and apply stucco or a stone veneer of some sort on the other side.
How would I go about this?
Do the stucco side first, I assume this is a building of some sort. If you use a synthetic stucco (EFIS) system then the exterior will be sealed from moisture. I have used LaHabra Stucco with good results. The base coat, I have used Insul-Bond Dry Base, can be applied directly to the block and is used to level the surface. Perma-Flex is used as the top coat and is tinted. This system is troweled on and dries really fast, hard to work with when by your self, but doable. If you know any stucco people you might want to ask for tips.
You can also apply a traditional portland stucco to the block. I don’t know if a bonding primer is needed, I would think not. A traditional stucco can be sealed with paint or clear sealer once fully cured, 30 day minimum. You could purchase all needed supplied from Home Depot for this type of stucco. The stone veneer is the same. The mortar (glue) used sticks directly to the block.
DOUBLE CHECK ALL OF THIS INFO!! I’m a painter not a stucco contractor nor stone veneer installer.
That takes care of the exterior. The interior is easy. Use a acrylic block filler primer to fill the pores then paint. Basically that easy.
Hi,
First and foremost, let me thank you for your time and the wealth of knowledge you provide on this site. I have spent the last hour reading through these posts and have learned a lot from everyone’s posts and your comments. Thank you!
That said, I want to ask a quick question and make sure I’m on the right track… I just purchased a cinder block building that the exterior has the split face blocks that were previously painted. Moisture has entered the walls leaving stains as evidence, so I will redo the roof, and then move to walls. My plan based on what I’ve read above and researched is to pressure wash the exterior walls and then apply the acrylic block filler as a primer and then come back over with DryLoc waterproof paint. Is that a good plan or is that overkill? Thanks again for your time and any advice you give.
Using the Dryloc isn’t overkill but might not be necessary. With the pores well sealed, blockfill primer, and good paint applied the block will be well sealed from the outside. The big thing is making sure the tops of the walls are sealed, roof or metal caps depending on the building construction. Windows, doors, roof flashings and roof penetrations also need to be in good shape with any sealants replaced were needed.
An alternative to using Dryloc as the finish paint is use a good elastomeric coating over the blockfill primer.
Hello, and thanks for sharing this helpful info! Is it possible to do a faux wood painting technique on a cinder block exterior? I’d like to make one wall look like each block is a piece of wood.
This wouldn’t be easy and might not last long. Each block would need to be smooth in order to use a graining tool, unless you can free-hand paint wood grain. Drywall mud might work to smooth the block, then prime and paint with the back-ground color. Graining will be a problem, normally this is done on a piece that is horizontal. With a vertical wall the paint/glaze mix or gel stain might want to sag. A thick gel stain would be your best bet then sealed with an exterior rated clear coat.
If this isn’t a well protected wall then your hard work will most likely crack, peel, flake or fade sooner than later.
Good Luck!!
This website is so helpful…thank you. I have a 15 year old basement with cinderblock walls and I’m looking to spruce it up a bit by painting the walls. The basement cinderblock is in good shape and it stays dry…but does have a little efflorescence that I’ll take care of during prep. I have a couple questions as I read through the different posts:
1) in my scenario, is it better to use a block filler primer or a typical masonry primer before painting?
2) in my scenario, do you recommend avoiding the use of any waterproofing sealants?
Thanks!
1) Depends, if the block was previously painted and most pores filled then block fill primer isn’t needed. A primer might still be needed if the old paint isn’t in good shape or there are many open pores. If the block is unpainted (never been painted) then a block fill primer is needed to fill the pores. Either a block fill primer or no primer depending on your situation.
2) No water proofing is needed.
The block has never been painted so I’ll go with the block fill primer. Thank you very much!
We live in South Louisiana what is the safe relative humidity for prime/painting cinder block walls,
Real world recommendation for safe max humidity is anything over 80% will be a major problem. Levels over 80% could stop the drying of the paint film altogether. High humidity levels will slow down the drying and curing of all primers and paints which could be a real problem if there is rain or other adverse weather on the way.
Optimum levels are 40-50% but 70% or under is fine as long as the temps are good, 75-80 or more. Paint will dry better in direct sunlight even when humidity levels are very high.
Some paints work better for high humidity areas. Sherwin Williams Resilience drys fast even when humidity levels are elevated. Talk to your local Sherwin Williams store rep about good paint choices for your area.
I live in Colorado and we have the opposite problem, way to low humidity. We can have single digit humidity and paint that drys so fast it cracks if to thick, the surface hardens while the inside film is still a liquid.
Need advice. I recently gutted and renovated my kitchen. It had a small backsplash from the 50’s. removing them exposed some block but mostly glue. The walls are cinder block and except for a few areas have been painted many many times. I’m torn between using a vinyl wall cover and wallpaper, using portland cement to smooth out the grooves, or just throwing in the towel and tiling over it. I can not imagine that I will ever successfully remove all of the glue. Any thoughts, tips, anything you can offer? It’s so much paint where it is painted that where the bare brick has been exposed it’s a noticeable difference in depth. Aghhhhh
Easiest would be chisel off the glue, patch if needed with drywall compound then tile. Patching only needed for major damage, the glue and tile will hide a lot.
For the other mentioned options; Prime the block then apply drywall compound to smooth it out. Prime the dry compound then either paint or apply some kind of vinyl wall covering.
For the drywall compound use either 45 or 90 minute dry powdered compound, much easier and quicker For the primer use either a good acrylic, Zinsser 123 or equivalent, or a fast drying oil base primer like Zinsser Coverstain or Kilz original.
Good day. I need advise, im about to paint a hospital which was previously painted years ago. The walls were not plastered instead they were cement bagwashed then painted so the texture is rough. Some sections the cement blocks were just painted. Would you advise i prime the walls first before applying two coats final coats or can I just clean the prepare the walls then apply two quotes as per the specification. You advise is highly appreciated.
Usually just a wash is all that is needed for painting. Especially if you use a quality paint, like Sherwin Williams Interior Super Paint or better. If there is a very hard enamel like paint, epoxy maybe, then priming will be needed.
Greetings, we just purchased a house in SoCal and we would like to have my backyard exterior block wall painted. My concern is the longevity of the paint for the exterior wall.
With a good prime and paint, how long would the paint usually last before start to chip off and make the wall look ugly!
Your advise is greatly appreciated…
As long as the entire wall is painted, includes the top and all sides, you should get 8-10 years before needing maintenance. The main concern is sealing all sides and the top to prevent water or moisture from entering the wall.
The maintenance should be easy, scrape a little and repaint.
Hi there! I’m painting my cinder block garage and have already primed the whole thing and put a first coat of masonry paint on a few weeks ago. Everything I read about rain and painting seems to refer to painting over bare surfaces. It’s going to rain overnight which causes dirt to splash up on the block. I want to power wash the first few feet of cinderblock around the garage in the morning, then paint the second coat within a couple hours. I’ll power wash a day before to get the few weeks of grime off but may get additional dirt with the overnight rain which I would want to wash off.
If it’s not fully dry is that an issue? The paint would be adhering to another layer of acrylic paint which I’m assuming is water based anyway. Thank you.
You should be fine since the surface is already sealed as long as it is dry to the touch. A couple things to consider are temperature and humidity; warm temps help with drying out the surface but high humidity can be a problem, slowing down the drying or stopping it altogether. Power wash with the least amount of pressure and give maximum time for drying before painting.
Thanks! I ended up power washing the day before and it most not have rained much if at all overnight as I didn’t have to redo it the next day
Though now I have another concern. I sprayed the paint and back rolled but ended up running short on the last 8 ft x 5 ft section or so. I poured what the sprayer pick up couldn’t get to into the paint roller tray, then ended up dunking the intake tube into a bucket of water and proceeded to use the water to force the left over water in the spray hose out onto the wall. I ended up getting water on the wall in some spots as a couple minutes later, the Greige paint had brown streaks in it. Water obviously ended up on the wall but I used the last bit of paint I had in the roller tray and rolled over those spots. It was dark by the time I was done but even if it looks fine, would there be any concern about the water getting into the paint on the wall? Sometimes water based paint is thinned anyway so I don’t think it would cause early paint issues.
It will be fine. The worst that can happen is you will need to repaint that wall sooner than you expected due to thinning the paint too much. If you think this could be an issue, sheen looks off or the section looks weird, just get another gallon and roll out the section feathering into the adjacent areas.
Hi there, thanks for this valuable information. I have been looking for tutorial on how to paint interior cinder block for days, and finally got here, so lucky!
I have recently bought a house built in concrete block in 1970s. The previous owner has painted the interior wall, it’s in good condition but old, the colour looks fading. I want to repaint it. There is no obvious cracks or holes, should I just clean it with brush and paint with any interior paint? The house doesn’t have any moisture problem by condensation, guess it’s not a problem solved with paint. Thank you.
Typically a cleaning is all that is needed. Just a wiping with warm water for surface dust or a little mild dish soap for some problem areas, no-rinse TSP can also be used for grease or particularly dirty areas. Then apply a good quality paint. When in doubt use a low voc primer, Zinsser 123 or equivalent.
We want to paint the exterior cinder block foundation on our home. It has never been painted, stained or otherwise treated in any way. If we use a product like Rollerrock exterior concrete coating from Home Depot do we just apply to the cinderblock (we already powerwashed it) without needing to prime first?
Second, I doubt we will go this route, but if we choose to go with latex paint do we prime first then paint or do we need to put a water seal on, then prime, then paint?
And lastly, is there a decorative paint-on product you would recommend? We have an adorable ranch house and I would love something that looks as nice as possible, which is why I’m looking into the RollerRock, and I don’t think plain latex paint will give me that. But I’m open to all suggestions! Thanks so much for any help/insight you can offer!!
Interesting choice that will look good, as compared to regular paint. I don’t know of any other easy to apply product that will look as good as the Roller Rock. Just plain paint.
You could use 1/4 tape and add grout lines, look like pieces of rock. I did notice the manufacture recommends a sealer after application. This would be a good idea if you add grout lines.
Son has a house built in the 1960’s. Interior garage walls are unpainted cinderblock which we want to paint. I see Lowes sells Valspar “Masontry, Stucco & Brick” paint that contains a primer which allegedly works in one coat. I don’t mind doing a second coat, and normally find that I have to do so, even with a paint that contains a primer. My question is whether I should use a different primer and then do a topcoat? Also do you recommend Valspar or a different paint?
Thank you,
Ray
There.s nothing wrong with the Valspar product. I think you will still need 2 coats for a good looking wall. It will work fine as a 2 coat system as long as it is applied thick enough and worked into the pores. If spraying, backrolling will be needed.
A block fill primer, the recommended primer for block, is nice as it is typically cheaper than paint allowing more to be used for a nicely sealed surface. Plus it does this faster and easier than most paints. It’s not necessary for aged block but is nice to use.
Hello,
We are about to embark on a big painting project and would greatly appreciate your advice.
We just added 5 rows of new cinder block to our existing wall. The existing wall is painted, most likely with an acrylic paint as the paint chip is a regular Valspar paint. The question is do we need to use an acrylic block fill on the new cinder blocks and a different primer, like Zinsser 123, on the previously painted blocks? In a previous post you noted the acrylic block fill doesn’t adhere as well to previously painted services.
Thank you so much for your time and expertise!
You can use a regular primer like 123 but a block-fill primer will do a better job, at filling the block pores and blending the new with the old.
The previously painted blocks shouldn’t need anything as long as they are clean and in good shape. The new paint should stick just fine. If you want to prime use the Zinsser 123.
Great info!
I am looking to paint a painted cement block townhouse. It’s mostly regular block with some rows that are split block. . Simply wash with warm water and paint with elastomeric paint? No primer needed? Is Benjamin Moore Aura exterior a good option also? And finally, spray or roll?
Thank you
Basically, yes that simple. Some things to look for;
You don’t have to use an elastomeric. Any good exterior house paint will do the job if applied thickly, 2 coats maybe, and back-rolled to help seal up the pores. Same hold true for the elstomeric. The Benjamin Moore Aura is very good paint and will hold up well, better than Sherwin Williams Emerald and most other top-of-line paints on the market today.
Hi,
Just getting ready to move into a house with a exterior fireplace box and chimney of cinderblock that has been previously been painted which has now been severely worn away. Do I need to be concerned about heat resistance when I select a paint? Also, I haven’t been on top of the roof, but does the top of the chimney need to be sealed and painted also? (I am hoping there is some sort of flashing installed that would take care of that area.)
Thank you.
The exterior cinder block can be primed and painted after prep as normal, there shouldn’t be any significant heat on the outside areas. The roof should have appropriate flashing to protect the roof sheeting and exterior wall from water damage.
Do you recommend paint or stain for unpainted exterior split faced block.
I recommend paint most of the time. Stain can provide a look that paint just can’t, like a semi-transparent masonry stain or white wash. 1 very good option is using a quality exterior flat mixed 50/50 with Seal-Krete. This can be sprayed directly on the block without the need for a primer and looks good. Can be top coated later with the same or a paint for a new look or quick maintenance.
Hello
Like so many others have said, I thank you for the great information you’ve provided and continue to provide, by answering questions 6 years since posting the article.
I’m an artist in Arizona and have a client who has requested a mural in the center 3 “panels” on her unpainted/unsealed split block wall. (aprrox 200 sq ft) One of the “panels” does have a half-hearted coat of paint, that seems like perhaps it was a project the previous owner abandoned after learning how labor intensive it is.
I have not worked with unsealed concrete block before and I have a couple questions. I typically use both acrylic and latex paint, with a retarder to prevent it drying too quickly. Would just a coat or 2 of primer sufficiently prepare the surface for my needs? Do you foresee any problems with only prepping the 3 panels I’m concerned with?
I have another question about sealing the completed work. I’ve previously sealed murals with a polycrylic matte topcoat applied with an airless sprayer, with good results, but still see fading quicker than I’d like. Do you have another suggestion for a topcoat that has better UV protection?
Again thank you for helping so many people for so many years!
God Bless!!
You’ll need to really seal the block well or it will suck up the water from your paints making them dry much faster. 2 heavy rolled or back rolled coats of primer should work. Test after the primer dries to see if it is sealed enough. You can always prime over the test area.
UV Protection: Not a whole lot of good choices. A spar varnish will be best but sticky and take a long time to dry, chasing drips will be your new pastime. The waterborne urethanes will work well but nothing lasts as long as you want. Varathane Spar Urethane, water-based exterior, works well but pricey. The Minwax Polycrylic is interior use so not a good choice for exterior use.
Hope this helps.
So far, I’ve not had any issues using polycrylic…meaning no one’s called me complaining…well not yet anyway…You are correct about the sparathane… Varathane Marine spar urethane is the only stuff that actually lives up to it’s UV protection claims,….I’ve only seen it in spray cans, and tbh I’ve never looked for gallons of it, but now I will.
As for applying the primer, it’s just me, I have no help available…. do you think I could get away without back rolling it, if I applied 2 coats, back to back, by working in very small sections with my airless sprayer?
Lastly, I also use a spray bottle of water along with retarder to better help blend the paint colors….it feels like I should give the primer a few days to cure before I start painting on top of it…What do you recommend?
Thanks again!
You’ll need to push the primer, at least 1 coat, into the block to fill the pores. Spray only, generally doesn’t work well. The material just sits on top allowing the pores to remain open.
How about this; Working small sections at a time, spray heavy coat then quickly backroll (keep a wet roller in a 5 gallon bucket with some primer, this way the roller won’t dry out). You’ll have to decide how big the section is. Temperature, wind sun exposure all change how fast the primer will dry. After this first coat dries, a couple hours in warm temps, go back over and just spray to help fill in where needed and provide a more even color.
The primer just needs to dry overnight in most cases. High humidity and cool temps can extend the drying time but acrylic primers, and paints, dry fast and are ready to top coat in just a few hours.
I have a cinder block construction barn. It was painted years ago, I have been pressure washing it. Do I need to remove all traces of paint or just peeling paint? I was hoping to paint a dark blue. What would you recommend? Primer(what kind) and what kind of paint? How long should I expect it too last? Thank you again. Oh and I have a graco sprayer with a 515 tip, will this work and should I back roll the primer and paint? Lastly, how many coats of primer and paint? It’s a old ground face block from the 50’-70’s
Hi, i have a newly built home in FL and im looking to point the garage which has cinderblocks on both sides. These concrete blocks have never been painted. Is a primer necessary?
Primer isn’t needed. Make sure to rinse of any dust or surface contamination first.
Thank you for your time and answers!
Do you know of any issues with applying an acrylic/latex system over interior CMU that was previously painted with an oil-based system and then later a water-based one? My painter is saying that applying a new latex coating on top of the existing water-based paint will lead to cracking and recommends stripping the previous coatings and applying a new oil-based finish system. I just can’t see how cracking would develop with another acrylic layer based on the discussions above. Stripping the existing CMU paint seems excessive. I am recommending a primer above the current finish followed by new acrylic paint.
A primer is needed. Stripping shouldn’t be necessary.
Hello Karl, I live in a high rise Condominium with underground parking. At the moment we are looking to paint the poured concrete walls of the entrance and exit ramps of the Garage which are obviously below ground and open to the weather. I have power washed all the loose paint and green mold from the bottom edge of the walls and am now looking for the proper application of paint to apply over the bare cement and left over paint on the walls. I have no idea what kind of paint is existing on the walls. Thx
Start with a universal acrylic primer. This will adhere to the existing paint plus seal the bare concrete walls. Application can be airless spray but make sure to finish up with a roller (back-roll) to help fill any open pores. After the primer dries a coat of good exterior acrylic paint can be applied.
I have scraped and wire brushed a concrete block that makes up three walls of my garage. There was some white powder and peeling of the approximately 15 year old acrylic paint as well as some dampness probably causing some bubbling in the past im hoping. I have addressed the water issue last year with a French drain and now the walls seem pretty dry. It is winter here in the Bay Area near San Francisco and rain has been heavy. Would you recommend i wait until weather is not so rainy and cold: mid 45-52 degrees f. And what should I prime and topcoat with please?
I would wait for warmer drier weather. Primer with a good acrylic primer, universal primer. Your local paint store will have it in stock, Kelly Moore makes a nice acrylic bonding primer. For the top coat any good acrylic paint will do, make sure it has a sheen (satin) for easier cleanup and longer lasting.
Im repainting exterior cinder block walls , theres 1- 1.5 feet underground before getting to foundation.
Is it necessary to dig down to foundation and repaint what is underground? Im in FL so it’s all sand and very difficult to dig a hole thay doesn’t fill itself back in .
No need to dig down to the foundation. For a nice finished look dig down a couple inches, paint past the normal sand or dirt line, then when dry push the dirt back.
Hello. My question is about my Cinder Block chimney (CMU). It is unpainted though we’ve had water repellent applied to it every few years to cut down on water intrusion in the fireplace. The repellent helps, but not completely and some water still soaks through.
We are now looking at painting the chimney instead and wanted to ask two questions –
1. Have you found that primering and painting provides better water protection than repellent spray alone?
2. and, if we still have active water repellent in our blocks when we go to paint, how to make sure the paint adheres?
On that last one, we’ve heard we should use an oil-based primer over water-based. Do you agree and how many coats would
you recommend of primer and paint for this?
Thank you!
Paint will be superior to any clear sealer and last way longer. Yes use primer. An oil based primer will have the best chance of sticking to the sealer. Prep; Wash to remove any dust or soot. Now apply the primer with a roller and brush making sure to work it into the block. Two coats of paint can be applied the same way. A good bonding primer should be used, Zinsser Cover Stain or equivalent will work well.
You shouldn’t have issues with the primer sticking as the block is rough and still has open pores, indicated from the water intrusion still occurring. If you think the sealer will be an issue simply wait until it burns off (oxidizes) then prep and paint. You can test the adhesion of the primer by applying some, 12×12 area, allowing it do dry then try to scrape it off with a putty knife or finger nail.