External Paint for concrete window ledges

[Jonoss]

Hi there would appreciate a bit of help and advice please

The paint on my external concrete window ledges is flaking and peeling yet again and needs to be repainted. What paint is best to use on horizontal external concrete surfaces such as these window ledges. I have in the past been using Sandtex external masonry paint but I understand this is not recommended for horizontal surfaces.

The colour of the ledges at present are black and they are in the sun a lot, would this also be a reason as to why the paint eventually peels and flakes badly.

Any advice on best type of paint to use and any tips would be warmly received.

Many thanks in advance

Jon

 

[Zampa]

Pre formed concrete sections are notoriously bad to paint....they have a very smooth surface and although it will soak water up......it is still quite impervious when it comes to paint coatings.

They are also highly alkali...so they may cause the paint to discolour..(normally white)

If you paint anything that is very absorbant what happens is, the water in the paint soaks into the surface, leaving just the paint film sitting on the surface..it need to key to something.......same goes when you put a thick coat of paint on bare plaster.....thats why we mist coat first.

Scrape all the remaining paint off...all of it, because whas not flaking off now will certainly flake off sometime in the future.

Then give the cill a slighty thinned coat of alkali resisting primer..allow it to weather for a few days then apply your masonry paint.