# Concrete Patio bubbling



## candleman98 (Apr 10, 2019)

I did a concrete patio last week, I spent numerous days getting four layers of paint off of it and sanded some edges down with a 36 grit sandpaper with a palm sander. Ran a concrete etch, allowed to dry out. Applied two coats of primer and two top coats of Sherwin Williams porch paint and I'm getting bubbling. I before and after pics. Owner has always had issues with this patio. I asked her did she get as much of the previous paint off as possible when she tried dealing with it .... she said no. I asked if she ever used a primer 1st or etched the concrete .... she said no. So I assumed the problem with the patio has been prep problems. Has anyone else run into bubbling problems like this, and how can they be addressed?


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## Jmayspaint (Mar 26, 2013)

If the slab was poured directly on the ground with no vapor barrier underneath, then moisture is going to come up through the concrete no matter what. Not saying that’s the case here, just that it’s an option. That’s why top coats like you used recommend a moisture intrusion test before proceeding. Taping some plastic down tightly for a couple days and seeing if it gets wet underneath. If it does, there’s a moisture problem that either must be dealt with or just don’t use a coating. 

Also, I’m curious what you mean by “primer”. 
As fast as I’m aware most concrete coatings don’t call for a primer. SW Porch & Floor enamel for example is direct to substrate and doesn’t recommend a primer. 

What primer did you use and why? 


Sent from my iPhone using Tapatalk


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## MikeCalifornia (Aug 26, 2012)

Jmayspaint coming in hot!! You are correct again. What he said.


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## EveryDay (Mar 23, 2019)

MikeCalifornia said:


> Jmayspaint coming in *hot*!! You are correct again. What he said.


Yup! Sounds like he nailed it again.


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## candleman98 (Apr 10, 2019)

I used a Behr primer .... because the concrete was so bad I wanted to build the substraight up to level playing field across the entire patio, before the top coat. I see your point that after a etch, I should have gone right to a top coat so the porch paint would have bit into the etch and had a better bond. A home inspector friend of mine and the SW help line stated the same thing about a moisture barrier not being in place and being the possible cause. When you pop the bubbles they are not wet, it seems like gas is blowing out of the concrete and blowing a bubble on the paint film. Thanks for your feedback.


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## stelzerpaintinginc. (May 9, 2012)

candleman98 said:


> I used a Behr primer .... because the concrete was so bad I wanted to build the substraight up to level playing field across the entire patio, before the top coat. I see your point that after a etch, I should have gone right to a top coat so the porch paint would have bit into the etch and had a better bond. A home inspector friend of mine and the SW help line stated the same thing about a moisture barrier not being in place and being the possible cause. When you pop the bubbles they are not wet, it seems like gas is blowing out of the concrete and blowing a bubble on the paint film. Thanks for your feedback.


Did you use this?
https://images.homedepot-static.com/productImages/c22e6919-5b47-48a2-902a-75878112d0dd/svn/clear-behr-premium-concrete-sealers-88001-64_1000.jpg

Although I would tend to agree with Jmays, something else to consider would be solvent entrapment, so you might review the drying times you allowed between coats. The link above for Behr Concrete Bonding Primer states less than 15% volume solids, which means 85% of what you're applying needs to evaporate before coating again. You said you applied 2 coats of this, so hopefully you allowed at least 4 hr min dry time between coats. If primer or paint or both were applied before the previous coats had evaporated, they'll continue to try and dry/evaporate after applying coats over-top, which traps the solvents trying to escape, cue the bubbles. This might be your problem, but only if when you pop those bubbles they don't go all the way back down to bare concrete.

Pop the bubbles. If they go all the way down to bare concrete, there's an underlying moisture issue with the entire slab. If bubbles only go down to one of the coats you applied, solvent entrapment is likely the cause.

Short of tearing up the slab to redo it, the HO could possibly mitigate the excessive moisture by cutting shrubs away from patio to allow sunlight, grading the ground to ensure water isn't funneling towards the patio, and installing different sizes of gravel around the outer perimeter of patio to aid in drainage.

Before attempting to do again, definitely test for moisture first.


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## MartyB913 (Dec 5, 2021)

I deal with interior works and renovations, but several times I wanted to help customers and concrete small areas and terraces. Bubbles appeared on the surface, and several customers stared anxiously at the concrete with the bubbles, wondering if it would last. I didn't want to get into awkward situations anymore, so I decided to work with experts on such things. I contacted paving contractors, who did the job flawlessly. I advise you that if you are not sure how to do the job, hire someone who will guarantee the job as in my case, there were no more worrying customer looks.


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## CndBrn (Dec 4, 2021)

I would take an angle grinder, with an abrasive disk, get as much as you can off. Use a wire brush, then broom it off. Get some Hydrated lime or (Portland cement), Hydrated lime has low water leakage and will bond well to masonry.(concrete)

In an empty can mix 3-4 cups of lime and add water to make a slurry, about the consistency of paint. I would lightly spray the area with water and sweep it first, then paint the area with the slurry.

Do a thin 1rst coat, followed by a slightly thicker 2nd coat and, finish it with a final thin coat. Wait at least a month before painting. You really don't need to paint but it would definitely help.


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