Doing some painting in an office building addition which is about nine years old.
Slab on grade
Steel frame, brick exterior
Forced air heat, vents in ceiling
The addition is about 60’x40′
We usually get about 18 inches of precip per yr., but we have been in a five year drought.
The carpet,(I think it is called Berber and is over pad) is bunching and wrinkling over the entire addition. In some places where they put down those clear plastic protectors under the rolling chairs, the carpet becomes wet and moldy. This is in the middle of the building away from walls and bathrooms etc. There are some conduits in the floor which have electrical, phone etc.
I really don’t have anything to do with the carpet problem, I am just curious as to where the water is coming from.
Replies
Concrete is not waterproof. Moisture can pass through it. Depending on how the subgrade was prepped under the slab, the concrete can wick ground moisture up into the living space. If nothing is covering the concrete, this very small amount of moisture will evaporate as fast as it comes through and you would never notice it. Cover it with carpet and the moisture cannot evaporate as rapidly and is held in place by the carpet a little like a sponge. Cover that carpet with plastic runners and the moisture has no chance to escape. This sounds to me like what you are witnessing.
Thanks for your reply. What baffles me is that there is carpet over slabs all around town without any problems. I'll bet most of them don't have any sort of waterproofing underneath. In our climate, I don't think anyone ever worried about it.
Could have something to do with soil conditions under slab. Site not prepared correctly for proper drainage and any water wicks into slab. Is slab below ground level?
It is above grade and doesn't have any apparent low spots. I don't know what soil is underneath.
As others have said, it could depend on the site conditions at that particular spot. Is it a low spot or is the soil particularly damp or are there other moisture conditions unique to that area, etc?
Not anything apparent. I can't remember what was there before. Maybe they poured over the old sprinkler system :)
It's probably because a plastic vapor barrier was not placed under the slab. Standard practice and required for any slab that is to be in a conditioned space - or at least it is required in every place I've built. Maybe the addition was not inspected when it was built?
There is no code enforcement here. Thats why I appreciate your input. I didn't have anything to do with this floor, but I'll sure VB anything I do.
It sounds like the moisture is coming up through the slab. Is there any way to seal the slab on the top?
There could be a leaking pipe under that slab that is contributing to the whole situation.
They're going to take the carpet up in about a week. It will be interesting to see if there is an obvious spot.
Did you smell the chair seats? Maybe someone has a bladder problem.
happy?
If it wrinkled the carpet on the whole place, I don't want to sniff :-)