Understand why condensation forms on the concrete slab under your home, and how you can prevent moisture from forming under your carpet. Learn how steps like keeping your gutter system clean and sloping soil away from your home can help redirect moisture away from your concrete foundation.
LESLIE: Tyson in New Mexico is having issues with a wet carpet . Tell us what’s going on.
TYSON: Well, I got a warm spot in my concrete slab that the house is on and after I laid down a – one of those plastic things for a rolling chair – desk chair …
TOM: (overlapping voices) OK.
LESLIE: (overlapping voices) Mm-hmm.
TYSON: A couple weeks after I laid that down there, there was moisture underneath it. The carpet was wet.
LESLIE: Because the …
TOM: Yeah, you got some condensation .
LESLIE: Yeah, the moisture can’t escape anymore.
TYSON: Yeah. And I was wondering if – I’m hoping it’s not a leak under there that’s causing that but I’m not sure what else it could be.
TOM: Well, if it’s only in that one spot, it’s probably condensation and what typically happens is the slab – which is made of concrete – is very hydroscopic, so it holds a lot of water. It was probably …
TOM: … evaporating some of that moisture up into the room space from below. Once you put the plastic chair protector on top of it, you basically stopped it from being able to breathe and as a result, you got condensation underneath.
The thing that you could try to do …
LESLIE: It’s like when you blow warm air onto a piece of cold glass and you see the …
LESLIE: … the condensation .
TOM: Yeah. The thing you could try to do is take some steps to reduce the amount of moisture  at the foundation perimeter; see if we can get that slap to dry out a little bit. Take a look at the gutter system, make sure it’s clean and free-flowing, all the downspouts extended out away from the foundation perimeter, make sure the soil slopes away; those are the things that …
TOM: … typically cause a lot of water to collect.
LESLIE: And use a dehumidifier .
TYSON: Alright. Well, thank you.
TOM: You’re welcome. Thanks so much for calling us at 888-MONEY-PIT.