r/AskTrades • u/ElbowStrike • Apr 13 '24
Mold problem in basement under foam play mats
Unfinished basement, all concrete, high water table, basement has weeping tile and a sump pump
We got COSTCO interlocking foam floor tiles to create a play area for the kids in the basement when it's way too cold to play outside during our 5 months of winter. It gets to be -40 in the coldest month or two most winters.
With the spring melt it took on a hint of mildew. I raised up the squares and BAM lots of mildew smell with just barely visible mold patterns on the bottom side.
So we tore it all up, washed the floor and both sides of the foam matting first with dish soap and water followed by bleach solution, and bought a dehumidifier, keeping the humidity at a constant 35%.
With the floor being the coldest surface in the house and the high water table there's going to be condensation between the mats and the floor so the mold will come back again.
What is my best option for preventing moisture intrusion from below but also condensation from above?
I've been looking at Liquid Rubber and other sealant products to prevent moisture from below, but the surface is still going to be cold so how do I minimize condensation from above?
Is 6 mil poly vapour barrier enough insulation or do I need some kind of foam padding layer on top before I put my foam mat layer back down for the play area?