Cheap DIY way to dehumidify a basement during a rainy spell?

May 2, 2011 11:43 AM

What is the best creative way to dehumidify a basement without buying an expensive dehumidifier? I don't want to run one constantly, but with all the flooding rain, I need to do something.

I live in Southeast Missouri, land of flooding rainwater at the moment. I rent a townhouse and I have a basement that is 1/2 finished with the other 1/2 simply a concrete room, separated by a paneling wall and door. I use the concrete room for laundry and storage. The finished room is where a bookshelf, my file cabinet, printer, dining table, and TV sit. I tend to use it for a home office...so not a lot of "living" down there but some.

It's been raining like a cow peeing on a flat rock for over a week, so everyone and everything is waterlogged. I do have 3 leaks in the basement, but I manage those by soaking up the water with towels then laundering them. The water hasn't completely covered the floor but will make large puddles if left alone. I pulled up the carpet in there this weekend because it was funky and I was tired of it (and could immediately tell a difference in the air quality based on my allergies). Now I have a solid concrete floor and three outer plaster/cinderblock walls (other walls are paneling and studs...not sure there's insulation in them).

Knowing that the rain won't last forever, and that normally the basement isn't that damp, does anyone have any ideas on how I can lower the humidity down there without spending $150 on a dehumidifier that I probably won't use forever? I have a couple of fans circulating the air right now. Anything creative I can do? Should I be running the central air conditioner (it's in the 50s today though...too cold!)? The heater? What about an electric space heater?

I'd guess the part of the basement I'm concerned most about is about 10ft x 10ft (maybe 10ft x 12ft...not good with judging distance!) with a door at the top of the stairs (leading into the living room) that I leave open for easy cat access. You can definitely tell where the air changes on the stairs though, both in temp and in humidity.

Any and all ideas welcome!

posted by MultiFaceted to home & garden (23 answers total)

If you have water coming up through the floor in the basement, it sounds like you need a sump pump.
posted by Mister Fabulous at 11:53 AM on May 2, 2011 [2 favorites]

Air conditioning will definitely pull humidity out of the air, and I don't think it will take a long time. We've had days where the humidity in our house hit 60% and it felt like a swamp. Turning on the AC for just a couple of hours would make a huge difference.
posted by COD at 11:53 AM on May 2, 2011

I agree w/Mr. Fabulous that you probably need a sump pump, but just having had one installed recently to replace an existing pump, it will cost way more than $150 for a dehumidifer (I paid about $600 incl. labor; you would probably need to double that for jackhammering the floor & installing tile and a crock). The AC may help.
posted by thomas j wise at 12:01 PM on May 2, 2011

You are renting this place, so have you told the landlord about the leaks?
posted by soelo at 12:07 PM on May 2, 2011 [2 favorites]

Hardware/home improvement stores sell desiccants intended to pull moisture out of the air. The large bucket sized ones like this might work for a basement situation.
posted by Rhomboid at 12:08 PM on May 2, 2011

I think the water coming up through the floor is more of a matter for a sump pump as well. But presuming that you get that addressed (by the landlord), there is a way to take care of the humidity -- you can find Damp Rid and other similar products in most hardware stores (and Google turns up that it's also available online, if you get stuck), and is inexpensive.

My super recommended that when I was smelling this strong mildew-y smell from under my kitchen sink that we couldn't figure out how to get rid of, and he finally suggested that under the principle that "if it is mildew, if you dehumidify there that'll kill it". It worked like a charm. Damp-rid comes in a few different sizes, to cover a few different room sizes.
posted by EmpressCallipygos at 12:11 PM on May 2, 2011

During that godawful weather last summer, my AC was filling a 5 gallon bucket per day.
posted by StickyCarpet at 12:12 PM on May 2, 2011

Nothing is going to help much if you've still got water coming in. If you had a closed system then heating the air would lower the relative humidity, but raising the temperature while more water is coming in will just cause the air to soak up even more water, and the humidity will spike as soon as that air cools off again when you turn off the heater or when that air circulates to a cooler part of the house. AC would help, but it would of course make the house cold. If there were a cheap and effective solution, there wouldn't be a market for dehumidifiers.

On preview, the desiccants Rhomboid mentioned are very expensive for the amount of water they remove. My basement is flooded right now too (greetings from swampy northern Ohio!) and I just ran my dehumidifier for a day with a Kill-o-Watt meter on it. It removed about 1.7 gallons for 55 cents worth of electricity. Assuming the 64-oz size bucket product is in a 64-oz bucket, it can absorb something less than half a gallon of water, for $9.97 plus tax or shipping. That would make it at least 55 times as expensive (not counting the cost of the dehumidifier itself, of course).
posted by jon1270 at 12:20 PM on May 2, 2011 [1 favorite]

Desiccants are usually sodium silicate. I've experimented with that, and it can bring down humidity in smallish, enclosed spaces. It absorbs water up to a point, then stops working until it is "recharged." To recharge, I use a cheap electric wok and a candy thermometer. Heat it, stirring occasionally, up to 125 degrees F. (It will start to scorch around 140 F.) Then it works again. Some of the desiccants I purchased, (during a period of very high humidity,) were already saturated when I bought them, and it had to be heated first to work.

You can figure out how much water is in, say, 10 cubic feet, with a particular humidity, and how much by weight you need to remove to change the humidity. I forget all the details, but for a medium sized room, you're talking 10s of pounds that your desiccant needs to gain.
posted by StickyCarpet at 12:30 PM on May 2, 2011

Sorry I wasn't clear on where the water is coming from.

I have three different cracks in the walls. One in the concrete storage room (manageable...I just move stuff out of the way and it magically runs toward the washer drain in the floor), and two in the finished part of the basement. So water runs down the wall and puddles on the floor. Landlord has been working on the issue for over a year so he's well aware. We'll save the discussion on his problem solving skills for another day...

The other end of the building (4 townhouses total) has a sump pump from what I understand, so their seepage must be worse. So far nothing is "seeping" from the concrete floor, but I wouldn't be surprised if that happens with all of this rain. Normally I get the leaking water during a really hard, fast downpour or an extended rain event, not every single time it rains.

The more I think about it, the more I think I'll probably go buy a dehumidifier today and try to sell it back to the landlord when/if I move out. It will most likely spike my electric bill for this month but once the rain backs off I doubt it would run much at all, so I guess I shouldn't worry about the extra cost. The rain is just. not. stopping.
posted by MultiFaceted at 12:31 PM on May 2, 2011

If you don't want to use a dehumidifier, the only other practical way is to get a lot of air flow. Open all the windows and use a couple of fans.
posted by Chocolate Pickle at 12:32 PM on May 2, 2011

it can absorb something less than half a gallon of water...

Okay, I may have wiffed that. DampRid says their product can absorb more than twice its weight in water, so it's closer to 25 times as expensive.
posted by jon1270 at 12:33 PM on May 2, 2011

You are a dream tenant but this is really your landlord's problem [I wrote before your recent update]

Along with the other things mentioned, is drainage from the roof sufficiently far away from the foundation? Extensions for the eavestrough downspouts are not too expensive (you can read more about that sort of thing in this PDF, a 'Homeowner's Guide to Flood Prevention' from the city of Edmonton -- scroll down to page 9).
posted by kmennie at 12:33 PM on May 2, 2011

Heat it, stirring occasionally, up to 125 degrees F. (It will start to scorch around 140 F.)

I might have wiffed that, too. On reflection, I think 140F was good, and it scorched at 160F.
posted by StickyCarpet at 12:39 PM on May 2, 2011

is drainage from the roof sufficiently far away from the foundation?

So we always had a very damp basement (this is in New Jersey) and during very heavy rainstorms, there would always be water in the basement. It would literally come up from the floor, at the walls. I went to home depot and looked around the roofing section, they had these plastic gutter extensions for like $8 each. I bought 6, then I went back and bought even more. The problem around my house was that the water coming out of the gutters was being drained right at the base of the house. Now it drains further away, in the middle of the lawn on one side and down the driveway into the street on the other, and it's almost completely solved our issues. Only once have we seen a small puddle develop in the middle of the basement at a low point but we don't (yet) have a sump pump. On the other hand, we got estimates of around $1000 for a sump pump (including jackhammering a hole into the floor). The extension tubes cost like $80 and have been 99% effective.
posted by exhilaration at 12:56 PM on May 2, 2011

I had water coming in one corner of the basement [opposite the sump, of course] during the big spring melt here in MN. I narrowed down the spot where it was coming in on the outside of the house [right next to a downspout], put an extension on the downspout and the puddling downstairs stopped in a couple hours.

On the dehumidifier front; try craigslist. Probably you'll find many in the $20-50 range.

Also, a shop vac might be easier than towels. Let a puddle collect, vacuum it up, then dump it down the floor drain.

There are "floor sucker" water pumps designed to pump puddles off a flat floor [like a sump pump, but it doesn't have to be at the bottom of a sump]; these may require more depth than your puddles, however [they did in my case].

There are also pumps that you connect to a garden hose that will suck a lot of water off the floor. I have seen versions of those that are far less than $20.
posted by chazlarson at 12:58 PM on May 2, 2011

We found a used dehumidifier at a yard sale for $50 for my parent's house. As a hack, we removed the holding tank, cut a hole in the frame bottom on the unit & placed it directly over the drain in the floor. Now it runs and drains as needed and doesn't have to be emptied.
It's still working after 15 years. Probably not the most energy efficient or quietest unit but they have no complaints.
posted by jaimystery at 1:33 PM on May 2, 2011

As a basement water leak veteran, dehumidifier is probably your cheapest option, with the only cheaper option being gutter extensions that redirect water away from the foundation ... which depends on the landscaping outside your house, etc. The morons who lived here last had the sump pump AND a gutter that drained half the roof dumping out 3 feet from the house so the sump cycled constantly, repumping out its own water. It sucked. We extended that gutter nearly 25 feet with a gutter extension and then a decorative stream with a waterproof channel that feeds down into a rain garden (depressed area of ground with plants that like wet feet). This was a bit of an undertaking but not terribly expensive, and it did solve the water problem on that corner and gave our sump pump a break. However, we own.

Another culprit was a concrete pad that had become slanted TOWARDS the house over time. Friends with a similar situation were able to just seal the crack between the concrete pad and the house foundation; we had to have the concrete pad replaced (very expensive).

In the end we had to replace our dewatering system, an undertaking that took 18 months of "unfinishing" the basement after a flood and waiting for the contractors, three motherloving DAYS of jackhammering, and around $5,000-$6,000 all told (including a new sump pump) just for the dewatering system (not including the cost of de-finishing and refinishing). And then there was all the refinishing. Just in case you want to put the fear of God into your landlord. :) He needs to have a basement water guy in to look at the water problem NOW, not after he's had the basement ruined.

Also, check your renters' insurance and see what it covers w/r/t water damage.

We run our dehumidifier a lot during the summer just to make the air down there drier and more comfortable. We dump the water on plants in the yard. It's not a huge spike in electricity use that we've noticed.
posted by Eyebrows McGee at 1:46 PM on May 2, 2011

There is an inexpensive solution to your problem and it involves exhausting the moisture laden air out of the basement. Desiccants will not work, you need to be removing gallons of water from the basement not pints. The problem is one of temperature and humidity, and this needs to be addressed not only now during the rainy season but also during the summer when the outside temperature is higher than the basement temperature.

In the summer with the windows open the cooler air in the basement will reach its dew point and deposit moisture on all surfaces, creating the perfect environment for mold growth. You don’t want this. The air needs to be either dehumidified or exhausted. Exhausting is cheaper.

What you want to be doing is pulling the coolest most moisture laden air off the basement floor. There are two approaches to doing this. Using an exhaust fan in a window (a bathroom exhaust fan would work) with a flex hose attached with the open end on the floor. Conversely, you could have a fan with an enclosure on the floor with a flex hose attached to that and run out the window. This approach is actually quite effective. See how you might do it here
posted by PaulBGoode at 3:20 PM on May 2, 2011

If there is a visible stream of water coming through a crack, you need to stop it with hydraulic cement. Really, your landlord does, but maybe you need to just get him to agree to pay for you to do it.
posted by dhartung at 4:13 PM on May 2, 2011

So I went ahead and bought a dehumidifier today. Figured I could talk with the landlord about it later when he's not dealing with all this rain (he owns other buildings in the area). I got home expecting to find water on the floor and there was none!!! The rain wasn't as torrential today so I'm guessing that the slower rate of rainfall plus the fan I left on today helped keep things under control. I'm thankful for that at least!

The landlord busted up and poured new concrete last fall and sloped it away from the building. He's also been working on the gutters but I don't think he has them the way he wants them yet. The only thing he hasn't done is seal the cracks, but it looks like that's been done in the past (before I got here 3 years ago). I can't say that he's been unresponsive to this whole mess but he's trying to do the DIY thing. I'm also the kind of person that isn't so good at waiting for someone else to fix what's bothering me which is why I'm doing my own DIY thing.
posted by MultiFaceted at 6:21 PM on May 2, 2011

I have a house with a 160 year old field stone foundation. This means that there is no practical way to keep water out of the foundation except by keeping water away from the foundation. To do that, you need to redirect water from the roof far away from the foundation. Think about it this way: all the water that hits your roof ends up going down the to the drip line or to the downspout (if you have gutters). if you have gutters, you need to make sure the gutters are clean and are properly installed (ie, water runs into the gutter instead of over) and that the downspouts are diverted as far away from the foundation as possible.

The other thing is how the property is graded. If the land is properly graded, surface water will run away from the house. If the land is graded towards your house, the water will go in your basement.

Sump pumps are generally only necessary if the water table is close to the level of the basement.
posted by plinth at 6:31 PM on May 2, 2011

Know anybody who works in a shoe or clothing store? They get tons of dessicant packets, and you can recycle them.
posted by theora55 at 9:01 PM on May 2, 2011