How to fix wet sandstone foundations?

dzg

hi - i posted recently about some water ingress near the windows in this area. see https://www.workshop.bunnings.com.au/t5/Whole-of-House/How-to-stop-water-coming-in-around-windows/m-p/312188#M28984

i was advised to dig up the stones a bit to see what was going on. making a new post as maybe it is a related but different question now.

it appears to my untrained eye that the sandstone foundations are having damage / erosion, i assume from wet soil. it's an area that doesnt get much sun, and the neighbour's property has poor stormwater drainage so the soil i think can stay wet for long periods.

hoping to get better trained eyes on it for thoughts. hope the photos are ok.

MitchellMc

Hi @dzg,

I don’t believe the sandstone that’s currently covered by soil is actually damaged. What you’re likely seeing is the difference between the parts of the foundation that were rendered and filled, and those that weren’t. Above the soil line, it looks like the rough-hewn sandstone blocks were coated with a render or cement-based filler to smooth out the irregularities and give a more uniform appearance when transitioning to the brick upper wall. Below the soil line, this process was never carried out, so the natural rough and uneven faces of the sandstone remain exposed. That can make it look like the stone has been eaten away or eroded, but in reality, it’s just the original unfinished surface of the blocks.

That said, long-term damp conditions can still cause issues for sandstone, particularly if water is allowed to sit against it without proper drainage. Improving the drainage in that area and ensuring water doesn’t remain in contact with the foundation for extended periods would be a wise preventative step. 

Please let me know if you have any questions.

Mitchell