I have a large farm shed which is built with concrete blocks, probably 45 years ago, however when the rain is driven by the wind it comes through the wall, l am looking for a exterior paint that will stop this problem in a grey colour. Regards Calum Mcpherson.
Assuming the wall is clean, dry and sound we can recommend Rust-Oleum Mathys Murfill Waterproofing Coating.
This is available in many Ral and BS colours.
New or unpainted substrates must be treated first with Rust-Oleum Mathys Primer 44 HS.