We have a sandstone basement and would like to paint it with a waterproofing paint. Can this cause damage to the sandstone, possibly weakening.

 

I don't know that I have ever painted any sandstone but I wouldn't think that paint could harm it - should protect it. Only drawback I can see is it will be painted sandstone and maybe not as visually appealing.

 

IF you feel you MUST coat the side of the sandstone wall, I would not recommend a paint coating.

Paint coating are just films that are typically chemically based. A cement-based coating would be more compatible with sandstone (high silica content sedimentary rock). A coating like Thoroseal (cement and fine silica sand with a polymer bonding agent) would be more compatible and provide the necessary breathing similar to the porosity of a sandstone.

If the foundation is sound and does not have water problems, I would not coat it unless you wanted a cosmetic solution. Typically, sandstone will last a few million years the last time I checked. Some sandstone may be slightly fiable and dust when rubbed, but you have to do a lot off rubbing to go through a sandstone wall.

Dick