Concrete Block sealing and painting


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Old 08-31-20, 01:04 PM
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Concrete Block sealing and painting

Hey Everyone,

New homeowner, first post on the forum!

I'm fixing up a ~50y old garage made with cinderblocks.

South wall is in bad shape with lots of big gaps. The exterior has been sealed over and over with different types of acryilic caulk, so i basically did the same, except i chipped out as much of the loose mortar as i could. I used Quikrete mortar repair, which worked out quite well, although i went through 4 tubes due to the size of some of the gaps. This wall faced the neighbors garage and no one sees it:

Question 1: Whats the quickest, easiest way to seal/paint this exterior block wall? I dont need it to look pretty, but I intend to do a nice job on the interior and dont want to let moisture in from the exterior side.


exterior wall with sealant

Moving on to the same wall, but the interior. This wall also had multiple holes from anchors. I repointed this wall using traditional mortar. Sloppy work (first timer) but the wall is going to be painted anyway. The plan is to roll on block filler on the concrete blocks, then spray on the final coat of paint.


interior wall in progress

Question 2: Exactly how clean must the wall be before applying block filler? Is it adequate to simply vacuum the walls with a shop vac? Do i really need to pressure wash (especially the inside of the garage?)

Question 3: small cracks, like in the picture, that were too narrow for acrylic sealer, what do I do with those?




interior small cracks

exterior small cracks

 
  #2  
Old 08-31-20, 01:21 PM
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I usually just take a broom and sweep the block - that is generally good enough. While it's best to chip out and remortar as needed it's ok to seal minor cracks with latex caulk.

I'd roll both the block fill and the finish paint using a 1' -1.5" roller cover.


almost forgot welcome to the forums!
 
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Old 08-31-20, 03:25 PM
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I can't remember the name of it but 20 years ago I used a product just for coating CMU walls. It came in a 5 gallon bucket like paint but was sanded and very thick. I troweled it on the block walls and it filled in the mortar joints and I ended up with a relatively smooth, with a sanded finish, wall that looked almost like stucco.
 
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Old 09-01-20, 05:50 AM
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Thanks guys.

@Mark, so the small cracks in pics 3 & 4:

pic 3 is interior, will the block filler take care of this?
pic 4 is exterior, you're saying i should put latex on these small exterior cracks, even if they're ~1/16"


And the outside wall, I'd really like to avoid going to the same amount of trouble as I'm going to on the inside since it's not visible. I just need the exterior wall sealed.

Is there a quick/easy, one-coat solution for this outer wall?

@Dane, sounds nice, but lots of work. I was even trying to cut out labor by spraying the top coat but consensus seems to be to use rollers.


I'll post some updates soon
 
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Old 09-01-20, 08:19 AM
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Blockfill is formulated to fill the pores of the block. It can sometimes seal minor cracks. IMO it's a safer bet to caulk any cracks that aren't re mortared. You could use an elastomeric paint on the exterior side. It both water proofs and seals minor cracks.
 
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Old 09-10-20, 12:24 PM
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Update and some plans:

Some updates:

I decided to give the bricks a quick gentle pressure wash before starting. So far I've cleaned and applied acrylic latex caulk (this) to the outer walls.


I tried to focus the caulk on the cracks, then blend it into the cinderblock so it wont be so obvious when I paint over it. Here's the 2 outer walls and the door header:





Only real question for now:

Can I use the same caulk to fill this small gap between soffit/trim and the block wall? Obviously it needs some work too.



any other advice is welcome.

I'll post a link to the paints and filler I plan to use.
 
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Old 09-10-20, 01:31 PM
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Yes, you can use the same caulking.
 
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Old 09-29-20, 10:38 AM
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Outside walls are complete. Some learnings and comments for anyone who’s interested:

I used Behr Elastomeric Masonry, Stucco & Brick Paint (https://www.homedepot.ca/product/beh...3-l/1000477461)

- Cleaning the wall: After ripping off trim and brushing away the old vine spores and bug nests with a wire brush, I pressure washed 2x. Decided I was done when I could run a bare hand across the brick & it feels clean vs sandy/dusty.

- Buy a lot of paint: 400 Sq Ft wall. Bought 5 gallons (expecting about 80-100 sqft/gal). Ended up doing 2 thick coats on both sides and a third light coat on the wall that's visible.

- 2 coats is mandatory: after 1 coat, there were a lot of little holes in the paint where I could still see block.

- 1.5” nap rollers were very helpful. Applying a bit of pressure to the roller (especially on the first coat) helped to get into mortar grooves, the texture of the cinderblocks & cracks.

- It’s much easier to fill cracks with a bit of caulk (even the 1-2mm ones) before painting. Getting paint to fill these cracks was a pain and after painting the caulk is invisible.

- I hindsight, I would have removed the tape (that protected the bricks) after each coat. I used a knife and carefully removed the tape after coat 2&3. Amateur painter mistake(?)

- I moved patio stones and raked the gravel away from the base of the wall so I could paint as low as possible. Ended up about 2 inched below the patio stone level. Seemed like a smart thing to do.

More to come RE the inside walls


 
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Old 09-29-20, 11:15 AM
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Looks good! I bet that wall along the fence was fun to paint
 
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Old 09-30-20, 06:15 AM
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Ya it's quite a workout just navigating the wet roller in that small space. Not to mention all the squats.

One last question on this thread then on to the next project (also concrete and masonry related!)

Seeing how this turned out, the plan inside the garage is to do the same.

Question:

If I want to pressure wash the inside of these block walls (the non-painted side) is is still safe to do so? Is it a bad idea to dampen this painted wall from the opposite side? If i do wash the inside of the wall should I go out of my way to dry it? dehumidifier? Should I let the paint cure for X days before spraying the inside? etc.

Thanks for all the guidance Mark, huge help & I hope it helps other people

 
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Old 09-30-20, 06:39 AM
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You can go ahead and pressure wash. It would be best to do on a warm day with low humidity so the wall can dry as quickly as possible. Then I would wait at least a week before painting to allow the block to thoroughly dry so you don't trap moisture within the wall and between the inner and outer paint.
 
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Old 09-30-20, 11:14 AM
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If you pressure wash make sure you let it dry good. Elastomeric paints are good at repelling moisture from the outside but don't like moisture that comes thru from the back side. I very seldom use a pressure washer inside.
 
 

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