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I have owned my house for 5 years. The outside wall of the laundry room in the basement is unfinished cinderblock. The cinderblock wall looks a bit unsightly, with dabs of paint, and the rough surface collects dust. The basement does not get water. In the summer, I run a dehumidifier. What are the pros and cons on painting the interior side of the cinderblock wall? If there are no real cons, what type of paint should I consider using?

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    I don't believe painting it will solve the dusty rough surface problem. The paint won't flatten the wall, and so it'll also slightly collect dust too. It'll be much easier to clean though. -- They sell paints specifically for block walls. I believe I see Dryloc mentioned often, although I've never painted one myself. – TFK Mar 6 '16 at 14:37
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pros - looks better, smoother surface that makes less dust

cons - seals the surface up well which prevents moisture from evaporating from the block. if its 100% sealed on the outside, it wont be an issue, but if you have any moisture, it will trap it in the block.

painting block is an extremely common commercial/industrial finish process. the trick is to use the right approach and material.

step 1 - fill and seal with concrete prep coat. this material is usually sprayed or put on with a texture gun, but if you want you could probably do it by roller (i wouldnt bother, just spray it)

https://www.dulux.ca/pro/products/masonry-coatings/perma-crete-ltc-concrete-block-and-masonry-surface

step 2 - paint over with whatever you want

omit the sealer and you can count on 10 coats minimum to seal it up properly.

  • This describes how to do it (thank you). Any thoughts on pros and cons? – Yehuda_NYC Mar 6 '16 at 16:25
  • I have no idea if the cinder block is completely sealed on the outside. It sounds like you are cautioning against sealing the inside unless the outside is sealed. Is it better for any moisture in the block to evaporate into the basement than into the ground? – Yehuda_NYC Mar 6 '16 at 18:23
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You need to paint the block first with block-filler paint then your finish coat.

However, if you regularly have moisture coming through the the basement wall the only way for it to dry is to the inside. By painting the wall you will trap the moisture behind the wall which will eventually cause the paint to fail.

One coat of a latex primer/paint may improve your appearance and still allow the wall to breathe.

Good luck!

  • I have not noticed any moisture coming through the cinder block wall. It does not change color when it rains. That is not to say that it might not happen in the future. So, am I safer just not painting the inside? – Yehuda_NYC Mar 6 '16 at 18:28
  • There are some products that are supposed to allow water vapor to pass through them. Basements are difficult places to create a warm dry environment. Latex paint will allow some vapor passage, more than oil based paint anyway. The big thing is if you trap the moisture mold and mildew will grow there. – ArchonOSX Mar 6 '16 at 18:32
  • Can you be clearer? Will sealing the inside of an outside wall cause more moisture to remain in the cinder blocks? If so, am I safer just not painting the inside? – Yehuda_NYC Mar 6 '16 at 20:13
  • It all depends on if your wall has moisture passing through it in to the basement in a large enough amount. Since you are only painting the part of the wall that is in the laundry room, I would try painting it. If it begins to fail in a few years at least it may still look better than what you have now. – ArchonOSX Mar 6 '16 at 20:59
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I have been waterproofing basement for over 10 years and this is 100% from my experience... not a sales pitch...

Basements should never be painted and I'm strongly against it for the following Reasons:

  1. Painting a wall will cause a damming effect in the wall which will stop the natural exhaust of water into the home... You will see this by the white substance known as efflorescence. Lyme and calcium, crystallization which occurs when water evaporates on concrete... anyone who has a block basement has seen this...
  2. the "Damming Effect" will allow the water that naturally plows into the porous block from the exterior side of the house enter in and fill up the voids in the block causing the water to hold and move further upward... everyone knows water flows down hill and trust me... Water will find a way into your home... So Painting will cause the following:
    • Mold
    • Pealing Paint
    • Water building in the wall
    • Breaking don of the mortar joints
    • and Water on your Floor...
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The only real cons are taking it off if you ever want to & putting it on in the first place. The pit holes or pock marks will need to be dabbed with a brush after your primer or sealer gets rolled-on & then again after your first & 2nd finish coats.

But, you're right & those are the pros of painting it. Keeping it maintained is nothing really, if you get some peeling or flaking in the future, you just scrape it off with a putty knife or scraper & paint over it with the rest of the wall.

An Exterior Masonry Sealer or Primer goes on first & then an Interior 100% Acrylic paint. You'll want at least 3 finish coats in order to flatten it out reasonably. Wait a day or even 2 between coats, including after the primer or sealer goes on. The wall will take a full month to cure.

  • Your last paragraph indicates you are talking about painting the exterior side of the wall. I was asking about painting the interior side of the wall. (I clarified the question.) – Yehuda_NYC Mar 6 '16 at 15:46
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    Sorry about that & thank you. I changed the finish coat paint, which would be the only difference. – Iggy Mar 6 '16 at 16:43
  • Please clarify more, are you talking about sealing (a) the side of the wall facing the outside, or (b) the side of the wall facing the laundry room interior? My question is about (b). – Yehuda_NYC Mar 6 '16 at 18:25
  • Actually, it just has to do with the cinder block or all cement-based surfaces. So, all Interior walls & all outdoor walls, regardless of exposed to weather or not. Cement-based products will continue to dust unless they're sealed & painting them without a sealer will just be temporary...the paint just falls off, peels & bubbles. – Iggy Mar 6 '16 at 21:37

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