Recently, there was a water leak under my house. Unfortunately, the pin-hole leak was on the top of the pipe (spraying upward) and by the time I discovered it, it had soaked the subfloor material.
The crawlspace access is at the far end house, away from where the leak was. I replaced the regular crawlspace access door with one I rigged up with a fan in the middle of it to facilitate the drying out process. There are several 3" x 5" vents around the perimeter of the structure.
My question is: Should the fan be placed so that it draws air from under the house or should it push air under the house? Or does it matter either way?
But ideally you place the fan so the output of the fan is blowing directly on the wet area(s) you need to dry out. A fan at one end of an attic or basement will be fine for preventing stagnant air and stagnant dampness long term. But will do very little to increase the evaporation rate of your wet subfloor.
Home Depot or equivalent can rent (or sell) you a fan used for just these kinds of purposes: high volume, high output velocity, and kinda noisy. But you’d need to be able / willing to drag it under the house all the way to the soaked area and aim the fan output up at the underside of the flooring.
Thanks. The clearance where the subfloor is, is about a foot and a half to 2’, so in addition to not being able to get one of those fans to the area (there are tighter spots along the way - ducting, wiring, jacks/supports, etc) I don’t think it would fit at the area.
Being in property management, we see leaks all the time, I could prob borrow a vendors fans (like the ones you linked to), but as I said, getting one to that spot, and having it function properly, is probably a non-starter.
Ouch. If you have wetness up on the top surface of the floor indoors, a fan like that would be useful up there. But if all the discernable damp is on the underside in the crawl space, a fan up there will be noise and waste; signifying nothing.
Yep, I appreciate your input but its a terrible situation.
The subfloor is some type of composite material that soaks up water like a sponge. The finish flooring in the kitchen was some kind of interlocking vinyl about 3/4" thick. When we decided to get rid of it, it was too tough to remove so I put HardieBacker over it and then tile.
So drying it from above is not happening. I did find this on the internet (prob AI) but who knows if its valid:
When drying a crawlspace, position the fan to exhaust air from the crawlspace to the outside. This creates negative pressure, drawing in drier outside air and expelling humid air, which is the most effective method for drying.
That’s interesting, because I’ve always heard the opposite, with the reasoning being that pulling (exhausting) the air tends to create less turbulence inside the room, thereby… increasing efficiency? I know next to nothing about this topic, so would like to understand it better.
This would not make me happy, either, but IMHO you need to replace that chunk of sub-flooring somehow. If it’s, say, particle board, it’s probably swollen and that part of the floor is structurally compromised now, plus, there’s probably mold setting up shop in that area and could be working its way into your house. Would your homeowners insurance cover that type of repair?
I would need to check. I replaced a section in the bedroom several years ago - same issue. But it was easy, I just pulled back the carpet and cut out the particle board and replaced it with 3/4" ply.
But if you read my description above about the kitchen floor, it’s a whole nother animal.
If the subfloor is indeed particle board, and not OSB, then any significant water exposure has destroyed any strength it ever had. OSB is a bit more common as a subfloor, and too much water will make it swell up but it retains its strength a bit better. The thick vinyl (really 3/4"?) and hardibacker (how thick?) and tile have created a composite floating floor above the subfloor that you’re unlikely to plunge through, but nowhere as near as strong and stiff as it should be. The whole 'nother animal is a BIG elephant, but between compromised strength and probably mold farm, that floor really ought to be torn up and replaced. On the other hand, I’ve had good luck setting up fans in odd places, blowing into a temporary duct of builders plastic folded over and stapled to long furring strip that could be slid into an otherwise inaccessible crawl space…
Yes, if not - very close to it. It was so thick that the locking profile (on both ends!) was impossible to rip apart. It had a base layer that brought the whole system to very nearly 3/4.
I’ve done this for enough odd situations to realize that a standard 10’ wide roll of plastic can have both edges brought together, wrapped twice around a piece of 1x3 and stapled to it, then a generic 2’ square window box fan grabbed from the neighbor’s trash fits snugly into one end of the plastic tube, with a sheet metal screw through the batten into the fan housing, and a few spring clips as desired to keep the plastic in place - when done with ventilation project, the fan is no more trashed then when you found it, all but a few inches of the plastic are still intact, and the roll of duct tape is still in the truck.
