Keeping Concrete Slab Dry
LESLIE: Greg in New Hampshire needs some help with a concrete slab. What can we do for you?GREG: I live on a lake and I have a bunkhouse that is located approximately 10 feet from the edge of the water …TOM: OK.GREG: … with a retaining wall in between.TOM: Now why do they call it a bunkhouse? Is that where you bunk when you get in trouble with your wife? (Leslie chuckles)GREG: I put my son out there; that’s why. That’s always an option, I suppose.TOM: (overlapping voices) (laughs) I was close.GREG: And what happens every time we get rain is the bunkhouse floor, which is a concrete slab, gets moist; gets wet.TOM: Right.GREG: And it does have a drain in the middle of it but it never gets that wet; I never have standing water in there. And I have put – I started – I tried to put a French drain around the perimeter, so I dug out probably about a foot down all the way around it and put crushed stone in there but that doesn’t seem to help at all.TOM: OK. Well, this is a monolithic slab? In other words, the slab and the footing are all one piece?GREG: Yes.TOM: When you dug down along the side, did you sort of feel that you were up against concrete?GREG: Yes.TOM: OK, so what you want to do here is move water away from the slab, not towards the slab. See, concrete slabs are very hydroscopic. They’re very absorbent; they suck up water in a very big way. So if you, on this bunkhouse building – do you have gutters on it?GREG: No.TOM: OK, so that’s a problem. If you’re dumping a lot of water around the foundation perimeter, it’s getting against the slab; it’s going to be sucked into the slab and drawn throughout the entire surface because it’s not that big. So what I would do is I would first put gutters on the building and I would get the downspouts extended, you know, four or five feet away. I think you’ll be amazed at what a huge difference something as simple as that will make because you want to move the water away from the walls so you don’t have as much water collecting there. When you did the drain around it, the trench around it, you probably made it worse.So you want to add soil, you want to slope it away from the outside walls and you want to extend the downspouts so that you try to keep the water away from the foundation perimeter. Do those things and then also paint that floor with an epoxy paint. Wait for a really good, dry day; use a two-part epoxy paint and that will stop some of the evaporation of the water into the building. And I think those two things together will result in this being a lot drier than you’ve ever had it before.GREG: Beautiful. I’ve got a bunkhouse I can hopefully stay in. Thank you very much for your help. (Leslie chuckles)TOM: (overlapping voices) There you go. Thanks so much for calling us at 1-888-MONEY-PIT.