Dry Out a Wet or Flooded Crawlspace
LESLIE: Chris in North Carolina is having foundation issues. Why don’t you tell us about the problem?
CHRIS: Well, you know, I went down after a few days of rain – about a week afterwards – and noticed it was a little damp in the crawlspace. Went under a little further and saw that my – the blocks in my foundation, you could see the water creeping up. So I’ve had several different dry solutions come out and I’m just trying to determine which is best because each one of them downplays the other.
TOM: Is this – are you talking about waterproofing contractors?
CHRIS: Yeah. Yes.
CHRIS: I would say waterproofing and also they would dehumidify and all that kind of thing.
LESLIE: Now Chris, are you only seeing this water after rain? You’re not seeing it any other times?
CHRIS: Now, down here in lovely Raleigh, North Carolina the – it’s been pretty dry here. So the fact that there’s moisture up to the middle of my foundation blocks, there’s definitely a problem. It’s coming in – because my house is actually right next to a berm.
CHRIS: So I imagine it comes down off the berm. It has no place to go but towards my house.
TOM: Alright. The solution here does not involve most of the systems that I’m sure these wet basement folks have been recommending, which I will just take a guess includes sump pumps and digging out foundations and this sort of thing. Is that correct?
CHRIS: Absolutely. Yes it does.
TOM: Yeah. Here’s what we would recommend you do. If you have a water problem that’s related to moisture, heavy rain, that sort of thing it always sources with outside drainage. So let’s start at the beginning.
First of all, I want you to look at your downspouts.
LESLIE: And your gutters themselves.
TOM: And your gutter system.
TOM: Make sure they’re clear. Make sure the downspouts are discharging at least four to six feet from the foundation; not at the corner of the foundation into little splash blocks.
TOM: But extend it out well away. Now, if you don’t want to see all these pipes coming off your house, trust me. Just do it for the short test and you’ll find out that it’s going to make a big impact and then you can finish how to neaten up later; perhaps by running them underground through solid PVC pipes or something of that nature.
TOM: The second thing is the angle of the soil around the foundation perimeter. If it’s flat; if it’s mulchy; if it has any type of like …
LESLIE: If it tilts toward the house.
TOM: Yeah, or landscaping edging that’s holding water in. If you have a moisture problem you want to have the soil slope away from the wall about six inches over the first four feet and what’s going to happen then is any rainfall that lands in that area is going to stay away from the backfill zone, which is that first four feet at the foundation perimeter.
Now, in terms of this berm that you say could be running water into the house. I can’t get a sense as to how much that may or may not be contributing to the problem. But if you have a hill that runs off in towards your house and you’re pretty sure that water from that hillside is getting in too close to the foundation, the solution is called a curtain drain, which is like a trench that is at the base of that hill that’s filled up with a bit of stone and then a perforated pipe and then more stone and then more grass so it’s invisible. And then that pipe collects the water; runs it around the outside. But I would not do that until I do these very simple things first.
Now, besides the gutters and the grading, get in that crawlspace and lay down a plastic vapor barrier across the entire floor. Is it a dirt floor?
CHRIS: Yeah. No, there was a vapor barrier but it has long since – the house is about seven years old and long since been destroyed at this point.
TOM: OK, so get a good vapor barrier down there. Try to have as few seams as possible.
And then lastly, if you want to try to move some air across there, you can put in some crawlspace ventilation fans that fit in the same space as an 8×16 block.
LESLIE: (overlapping voices) They replace a cinder block.
TOM: And then what you want to do is hook those up to a humidistat. So then when the humidity gets high down there the fans will come on and they’ll pull drier air across the crawlspace and dry it out.
CHRIS: Where can I get something like that?
TOM: Oh, you can get them online. You can get them at home centers. They’re fairly available.
CHRIS: And they’re called what again?
TOM: It’s a vent fan for a crawlspace.
CHRIS: OK, I think I’ve seen some that are like solar-powered. Is that …?
TOM: No, no, no. These would be 120 volt …
CHRIS: OK. Alright.
TOM: … and you want a good-quality one because it’s not like you go down there everyday. You just want it come on and work reliably. You may have to buy the humidistat separately.
But that combination of suggestions will dramatically dry out that crawlspace. The problem with calling the waterproofers is they only know how to sell you an expensive solution and this is one that involves a lot of common sense and a lot of practical work and not a lot of expense.
CHRIS: Now, what if I have shrubbery fairly close to that side of the house?
TOM: Yeah, that could be a contributing factor but before you tear up your shrubs work on the gutters first because that’s the number one thing that causes this.