# Best Practices for Recoating Peeling Concrete Block



## BhamPainter

Hey guys,

I recently got a bid to repaint a private school's gym with some serious concrete issues. The interior paint is getting blown off the walls by moisture, and the exterior is peeling in a number of areas. I've already told them that I think they need to have the roof checked (I suspect the moisture is coming in from the top), but beyond that, I'm looking to pick people's brains about the best way to approach recoating the exterior.

Most of the masonry painting that I've done in the past has been on residential structures where the underlying paint seems pretty sound. I've primed bare areas with standard acrylic primer and coated with standard exterior latex. My results have been great.

This is different mainly because there is clearly an extensive problem with moisture entering from outside. I'm sure that the previous painters were a blow 'n' go operation, and probably just used contractor-grade latex, and it's failing in a lot of places.

The options I'm currently considering are:

a) Pressure-washing/scraping, then spot-priming bare concrete block with block filler and top-coating with Regal Select or Aura.

b) Same prep, then spot-priming with block filler and top-coating with elastomeric.

c) Same prep, then full-prime with block filler and top-coat with Regal Select or Aura.

Obviously, the cheapest option would be a, but I'm worried about whether or not it will be waterproof enough to prevent moisture getting inside. Thoughts about the best course of action?

Also, on the interior, will a vapor barrier primer help in any way?


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## IPCSpecialists

I would suggest blasting the old coating off, applying an epoxy primer then an acrylic or polyurethane top coat depending on the protection they want. If you apply an acrylic directly to the block, it will only peel again.


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## journeymanPainter

For the exterior I would pressure wash with a turbo nozzle, then prime with block filler, then finish with an elastomeric. 

Sent from my SGH-T989D using Tapatalk


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## IPCSpecialists

Any decent block fillers I am familiar with like Tnemec Series 130 ENVIROFILL require an ICRI CSP 2-4, and must go directly to block. Why would you put that on top of a failing coating?


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## journeymanPainter

IPCSpecialists said:


> Any decent block fillers I am familiar with like Tnemec Series 130 ENVIROFILL require an ICRI CSP 2-4, and must go directly to block. Why would you put that on top of a failing coating?


Are you a rep for tnemec? I wouldn't trust there block filler to fill a hole in the ground....also the rep he had didn't even know the spread rate, or know how to mix the epoxy we were using 

Heavy spray and a good back roll didn't work for us when we did an animal testing facility, but the normal latex block filler (just rolling) worked great everytime I've used it

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## IPCSpecialists

journeymanPainter said:


> Are you a rep for tnemec? I wouldn't trust there block filler to fill a hole in the ground....also the rep he had didn't even know the spread rate, or know how to mix the epoxy we were using
> 
> Heavy spray and a good back roll didn't work for us when we did an animal testing facility, but the normal latex block filler (just rolling) worked great
> everytime I've used it
> 
> Sent from my SGH-T989D using Tapatalk


No I am not a rep for Tnemec...It's just a sold product. I've seen it used many times in animal shelters, exterior block at WWTP's and sports facilities without a hitch with proper surface preparation. I, personally, wouldn't consider a latex block filler commercial nor industrial, but that's my opinion..

It is cementitious so I could see why it wouldn't work if say, the surface was only pressure washed and had an old coating on it. Which may have not been the case.

Still curious why you'd suggest applying block filler to a failing system.


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## Jmayspaint

Seal Krete


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## Oden

You can't see it but
Knock off the loose and paint it. I've never seen block filler peel but if it somehow did refill the bare block.
A-100 grade is gonna hold up as good as anything that costs more as finish
If the roof is leaking down into the block cavity anything you put on it will fail at about the same rate
A lot of times them kinds of failures are limited to certain areas and are usually caused by the gutters, downspouts, or scuppers having leaks and like waterfalls running down onto them certain areas


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## journeymanPainter

IPCSpecialists said:


> No I am not a rep for Tnemec...It's just a sold product. I've seen it used many times in animal shelters, exterior block at WWTP's and sports facilities without a hitch with proper surface preparation. I, personally, wouldn't consider a latex block filler commercial nor industrial, but that's my opinion..
> 
> It is cementitious so I could see why it wouldn't work if say, the surface was only pressure washed and had an old coating on it. Which may have not been the case.
> 
> Still curious why you'd suggest applying block filler to a failing system.


Unless the previous painter did a really crappy job prep wise, and used an interior paint I think that the OP is right, its a roof issue. I would actually put that in writing for the warranty staying that the roof needs to be inspected before any painting is to be done

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## BhamPainter

journeymanPainter said:


> Unless the previous painter did a really crappy job prep wise, and used an interior paint I think that the OP is right, its a roof issue. I would actually put that in writing for the warranty staying that the roof needs to be inspected before any painting is to be done
> 
> Sent from my SGH-T989D using Tapatalk


When I mentioned the roof leak to them, they said they spent "a couple hundred bucks" to fix a previous roof leak. They said they know it's fixed because water no longer runs down the interior wall. 

Also, I would say yes . . . they did a pretty crappy job prep wise. The areas where the exterior coating is failing peel down to bare concrete block, as do the interior areas. It was last painted roughly three years ago.


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## Paradigmzz

Fix roof leak. Prep. Block filler is great for filling pick holes in CMU.

Dont see the point of block filler unless the block truly is bare. 

My biggest and only point here is this: using an elastomeric with a top down leak or pinholes more than 10 a square foot is going to make your paint swell up like a balloon.A100 is all youneed for a top coat.


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