Drying out crawlspace after flood

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Flyover

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Our neighborhood flooded pretty bad yesterday and some people lost their homes, but we got off with water just up to the foundation in the back. (That didn't stop the journalists from putting me and my family on the front page of the news, those bastards. But I digress...) It's a beam-on-pier ranch and we have a crawlspace a couple feet high. So, a literal crawlspace, not a crouchspace. I'm certain water got in there, and it smells like it in certain parts of the house now. Gonna go to the hardware store and pick up a couple of dehumidifiers to put down there, but I've never done this before.

Any recommendations on what type of dehumidifier to buy? Where to place them? Anything else I should know? As far as I know, my crawlspace is not vented.

Another factor to be aware of is that I'm not sure I can access all of the crawlspace. I think I'd need to kind of burrow down into the gravel to get past the joists, and I'm hesitant to do that, especially now that it's all wet.
 

Sparky617

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Has the water all drained out? Is the ground covered with plastic? You'll never be able to dry out the earth below your house, so you want to contain that below 6 mil plastic. You'll want a dehumidifier that can have the drain attached to a hose and let gravity carry it out of the crawlspace. Emptying a bin will become a several times a day affair for the the next few weeks. If air is getting in you're going to be trying to dehumidify your neighborhood, a losing proposition.
 

Flyover

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I switched strategies. Now I've got a couple box fans down there and I'm blowing that air in a very controlled way up and out the front door.
 

Flyover

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@Jeff Handy and @Sparky617 those are both great ideas but probably won't happen, both due to cost and lack of access.

I wish I'd thought to take a picture of my fan setup, it's pretty ingenious. The entry to my crawlspace is in the bottom of the front hall coat closet. I've got one fan on the ground in the crawlspace at the bottom of the closet, leaning on a joist and blowing diagonally up (because my crawlspace doesn't have enough clearance to put a box fan upright); then I've got another box fan in the doorway of the closet, blowing out. It's leaning against a music stand with a rack that's also angled in a way that helps guide the air up and out of the closet. Then I've got an oscillating fan with the oscillator turned off, blowing out the open front door. I've got a big clear sheet of plastic -- it's a cut-open bag from a recently purchased mattress -- gaff-taped up across the hallway so the air can't go back into the house. The front door is open with fans running from after breakfast until just before the kids go to bed. We've had this setup for two days now, and we'll do it one more day tomorrow. Might resurrect it later if we still notice a mildewy smell even after a few sunny days.
 

oldognewtrick

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@Jeff Handy and @Sparky617 those are both great ideas but probably won't happen, both due to cost and lack of access.

I wish I'd thought to take a picture of my fan setup, it's pretty ingenious. The entry to my crawlspace is in the bottom of the front hall coat closet. I've got one fan on the ground in the crawlspace at the bottom of the closet, leaning on a joist and blowing diagonally up (because my crawlspace doesn't have enough clearance to put a box fan upright); then I've got another box fan in the doorway of the closet, blowing out. It's leaning against a music stand with a rack that's also angled in a way that helps guide the air up and out of the closet. Then I've got an oscillating fan with the oscillator turned off, blowing out the open front door. I've got a big clear sheet of plastic -- it's a cut-open bag from a recently purchased mattress -- gaff-taped up across the hallway so the air can't go back into the house. The front door is open with fans running from after breakfast until just before the kids go to bed. We've had this setup for two days now, and we'll do it one more day tomorrow. Might resurrect it later if we still notice a mildewy smell even after a few sunny days.
Do you have any foundation vents?
 

Sparky617

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@Jeff Handy and @Sparky617 those are both great ideas but probably won't happen, both due to cost and lack of access.

I wish I'd thought to take a picture of my fan setup, it's pretty ingenious. The entry to my crawlspace is in the bottom of the front hall coat closet. I've got one fan on the ground in the crawlspace at the bottom of the closet, leaning on a joist and blowing diagonally up (because my crawlspace doesn't have enough clearance to put a box fan upright); then I've got another box fan in the doorway of the closet, blowing out. It's leaning against a music stand with a rack that's also angled in a way that helps guide the air up and out of the closet. Then I've got an oscillating fan with the oscillator turned off, blowing out the open front door. I've got a big clear sheet of plastic -- it's a cut-open bag from a recently purchased mattress -- gaff-taped up across the hallway so the air can't go back into the house. The front door is open with fans running from after breakfast until just before the kids go to bed. We've had this setup for two days now, and we'll do it one more day tomorrow. Might resurrect it later if we still notice a mildewy smell even after a few sunny days.
Covering as much as you can with 6 mil plastic will help limit the amount of moisture coming into your house. Covering it all and sealing it to the walls is the ideal way of doing it. You might be able to expand your reach with extendable painting poles. Access can be tight in crawlspaces, and it sounds like your access is pretty tight.
 

Flyover

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@oldognewtrick
As far as I know, my crawlspace is not vented.
@Sparky617 With the way my crawlspace is, covering anything more than the approx. 4'x6' section I have access to between joists/ducts would be very difficult. It just isn't practical, maybe unless I hire a pro, and I don't think we'll be in the house long enough to make that worthwhile.

We ran that fan system I described for three days including one sunny day and now the smell is mostly gone. Another day or two of sun coming up should get it back to where it isn't a problem.
 

Sparky617

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If your crawlspace isn't vented, adding a dehumidifier down there would definitely be a good idea. In new construction I'm a big fan of conditioned crawlspaces. I have a full basement, but most of my neighbors have crawlspaces with dirt floors covered with 6 mil plastic and foundation vents. There are companies around here that will come in seal the ground, seal the foundation vents, insulate the exterior foundation walls and add HVAC to condition the space. It isn't cheap, but it does prevent a lot of problems, especially in well insulated and sealed homes. Older leaky homes it doesn't present as much of a problem. One sign of issues with excess moisture in a house is peeling paint on the siding.
 
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