Damp Proofing

What is the best product for sealing a stone lintel to prevent damp penetrating into the house?

Anonymous user 28/02/2024 - 2.51 PM

I have a house dating to 1894 with natural stone window sills which bridge the cavity. I believe the stone is millstone grit, common in the Blackburn (Lancs) area, a bit like sandstone. The lintels are horizontal so rain does not run off. I have removed the plaster from the internal walls and found that the lintels are damp. The sealant between the uPVC window frame and the lintel has lifted, so I will re-seal that, but I want to address the porosity problem at the same time. Which system will give me the best long term solution for stopping water being absorbed by the stone sill and making it's way through to the inside of the house? The worst sill is south facing. I guess options could be to remove the old paint and repair any cracks (what with?... just 3:1 sand/cement mortar with 50/50 PVA??), then: 1. Repaint with some brand of masonry paint, or 2. Seal with 50/50 PVA/water mix then repaint , or 3. Do either 1 or 2 then apply some sort of water repellent surface coating or 4. Apply a product (like Dryseal from Platinum Chemicals) which penetrates deep into the stone, or 5. Do option 4 followed by either 1, 2 or 3. 6. Other?? Please advise the best method and brands, as I rather get it right first time than learn by trial and error!