28 Nov 2020

Masonry Paint & Damp Wall Problems

Masonry Paint & Damp Wall Problems

Several customers have asked recently if they can apply our Extreme Climate Water Seal over masonry paint or even underneath it to stop rain driving through their walls.    Usually this question arises because re-painting hasn’t worked and the problem has come back.

However there are some key points to bear in mind before trying “mix and match” solutions….

1.  Quality Masonry Paint works!

If you are using a good quality masonry paint like Kingfisher Weatherflex the polymers in the paint should provide a fully waterproof (and breathable) shell.   Avoid cheap “white bucket” and “trade special” masonry paints as they are usually cut with fillers and water to save on the expensive polymer component.    It should not be necessary to “over-treat” masonry paint with Extreme Climate or any other water repellent

2.  Use “Stabilising Solution” NOT “Water Seal”!

When preparing the surface remove any loose paint and prime the surface with Stabilising Solution to ensure that the new paint can “key” into the substrate.  This improves the quality of the paint finish and the water resistance.  DO NOT prime with “water seal / repellent” as these are formulated to shrug off water droplets.   Masonry paints are water based and will simply not stick to a surface treated with “Water Seal”.

3.  Check for cracks and defects.

It is surprising how far water will travel through a wall.  A crack in one place can show up us a damp patch several feet away inside the building.  Re-point any decayed mortar joints to make good before painting.  Also check for leaky gutters and decayed downpipe fixings as other pathways for water.

There is detailed guidance in our “How To Re-Coat Your Home” guide at https://static.kingfisheruk.com/specs/howto/weatherflex.pdf

If you have any questions about how to diagnose damp walls, feel free to call us for guidance.