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A section of the wall in our house developed flakiness due to dampness, prompting us to undertake repairs. Specifically, the affected area was located behind an air conditioner. It appeared that poor initial plastering, combined with water leakage from the old AC indoor unit, caused the concrete to become flaky. Consequently, the old plaster was removed, exposing the brickwork, and a new layer of plaster was applied by a professional mason. Once this was completed, I proceeded to apply a layer of waterproof putty, specifically, this product.

After allowing the putty to dry, I noticed certain areas that appeared thin, so I decided to apply an additional layer without sanding the surface. My intention was to maintain the layer's thickness. Although the resulting surface was not perfectly smooth, it wasn't of great concern since it was a wall hidden behind an air conditioner. The main objective was to protect it from dampness for as long as possible.

Once the second layer of putty dried, I proceeded to apply a waterproof primer. I used this particular primer, which, according to the technical data sheet, could be thinned with water. However, it did not explicitly state whether dilution was necessary. To clarify, I consulted with the shop owner from whom I purchased the primer, and he confirmed that thinning the primer was not strictly required.

Consequently, I applied the primer as is, without diluting it. As it began to dry, the wall started to exhibit flakiness:

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Before long, the entire wall peeled off. I believe the primer removed a layer of putty as well. All labour lost.

In order to rectify the situation, I will need to apply another layer of primer. However, before proceeding, I need to understand why the primer peeled off. Do you have any insights into the possible reasons behind this issue? I believe I have to thin the primer, right?

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  • How long between putting on the plaster and putting on the primer did you wait? Plaster takes time to dry/cure.
    – crip659
    Jun 4, 2023 at 11:58
  • @crip659 You mean between the second layer of putty and primer? 12 hours. The putty technical sheet said curing time is 6 hours. Jun 4, 2023 at 12:00

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The curing time is the time for it to be dry to touch and to not fall off.

You need to wait at least two days for it to dry. Even the tech sheet on the product you have used, says this

Drying Time - Surface Dry: 4-6 hours. Hard Dry: Overnight

This site says 24 hours (but its a general comment, not specific to your product)

Most will take about 12 hours, but leaving it for 24 hours will ensure it is completely dry throughout. Next, you can sand it with a sander and then paint.

Drying Time

I am not associated with this site or the products therein.


You can use a heater to speed up the process. I would recommend that you put a heater in the room with the door closed for 8-12 hours.

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