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Should I be concerned about flaking paint on house foundation?

Hi all,

We moved into our new home October 2024 and had concreting completed post handover. It was all going great and we were happy with how it turned out, but with the onset of Winter we have noticed some flaking paint on the foundation.

For context, the foundation was "waterproofed" prior to concrete pour with this black paint. Our house faces North and takes on most of the wind and rain in Winter. The rest of the house is fine and peeling is only at the front.

I am assuming water is getting in (from any of the imperfections) and behind the paint and causing it to do this? I also assume painting it again would have the same issue, so should we just leave it alone as moisture is getting out? It doesn't look very nice and is an eyesore when I pull in the driveway.

Thanks,

Harry

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JacobZ

Hi @haitchb,

The perspective of the photo threw me off a bit, but I am fairly confident I understand what is going on.

You can see there is plascourse coming out of the wall where the solid red arrows are. I believe this is your dampcourse (DPC), meaning water should not be allowed to touch anything above this line.

This waterproofing paint appears to be applied to the side of the concrete foundation, which is known as slab edge waterproofing, and is important because the slab is particularly vulnerable to moisture penetration due to the proximity to the ground.

Now that the pathways have been poured, it is impossible to recoat the entire side of the slab, which would be an ideal fix, but I think the best course of action is to recoat what you can with Crommelin Exterior Grade Brushable Waterproofer, ensuring one continuous coating with no gaps is applied to the whole area.

You should start by removing as much flaky paint as possible, then applying Crommelin Waterproofing Membrane Surface Primer, before overcoating with the waterproofing paint.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

haitchb

https://www.workshop.bunnings.com.au/discussion/comment/53906#Comment_53906

Hi @JacobZ,

Thank you for your informative answer. You are correct in that the red arrows point to the DPC sticking out between the render and house slab. Prior to the pathways being poured, the slab edge was painted in this waterproofing paint down to the vapour barrier (?) under the house.

Appreciate you sharing those products. A shame (for the perfectionist in me!) that the end result colour is grey, but I suspect we would need to do the whole house anyway where the slab edge is exposed. Given the scale of the job and the importance like you mentioned, I think I will reach out to a local waterproofing company to discuss. Also a job much better suited to the warmer seasons so any moisture can dry out!

Thank you for your help and have a good weekend,

Harry.

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