How to fix wet subfloor?

lisyloo725

Hi troop

I recently bought a house that has a fairly stinky ground floor bedroom front right of my house.
Being English I’m not 100% sure of the Aussie lingo, so I’ll define here:

*carpet level floor - I’ll call that the floor

*about 50cm below that is muddy sandstone - I’ll call that the subfloor.

I have cleaned all the mud off the subfloor - so it’s bare sandstone now.

Despite running megaflo Agi drains across the front and down the right side of the house, the sandstone subfloor gets puddles forming. I dry these up and the next day they’re back. About an inch deep.

what can I use to prevent the rock from ‘crying’?? This would be on the inside of the house (in that subfloor space).

When fitting the Agi drain, I waterproofed the outside of the brick walls with Cromellin before putting corrugated plastic sheet up against the waterproofing (to protect it), followed by blue metal gravel, a bit of topsoil, then decorative gravel.

we also fitted a super powered sub floor ventilation system - whic doesn’t seem capable of drying out the inch-deep puddles 🙈

your thoughts are appreciated!!

MitchellMc

Welcome to the Bunnings Workshop community @lisyloo725. It's fantastic to have you join us, and many thanks for your question about subfloor moisture.

Would it be possible to post some images of the area so our members have a better idea of what you're working with? Let me know if you need a hand uploading images.

It sounds like you have an elevated floor and a house built on a sandstone slab. Despite waterproofing, moisture might be travelling through the rock and then breaching its surface, creating puddles. You could potentially try waterproofing the entire rock surface with Dunlop 4L Damp-Proof Waterproofing, although it's not specifically designed for a natural stone. You'll need to ensure the sandstone is very clean before applying the waterproof to ensure it has the best chance of binding to the surface.

Please let me know if you have any questions.

Mitchell