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moisture in crawl space - navigating my options

Questions, answers and advice for people who own or work on houses built during the 20th century.

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Re: moisture in crawl space - navigating my options

Postby downtowndahlgren on Fri Sep 30, 2011 10:54 pm

Danno, what is your concern/anger regarding installing a vapor barrier/liner on the foundation wall, as long as there is a dehumidifier and, preferably, a sump pump as well? I can control the humidity level on the dehumdifier so it's below 50%, whereas prior to installation of the system, my crawlspace was literally a swamp. Not so now. Just wondering.
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Re: moisture in crawl space - navigating my options

Postby Danno on Fri Sep 30, 2011 11:14 pm

It's dehumidified on the inside of the barrier, but if the barrier is on the interior side of the foundation then the foundation itself is still saturated with moisture. Eventually this moisture will destroy either the mortar or the stones/bricks that it's made of. French drains might be better than nothing, but they are more for quantifiable amounts of water than they are for condensation or general moisture.

Best case scenario is to put in a good drainage system, seal the outside of the foundation, and condition the inside of the foundation (with or without a vapor barrier on the dirt ground)

Otherwise you might as well staple plastic to the underside of your joists and fill the basement/crawlspace with dirt.
1858 Italianate and Gothic Inspired thingamabob
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Re: moisture in crawl space - navigating my options

Postby thelyricwriter on Wed Jun 06, 2018 12:03 pm

I never knew how dangerous moisture in your crawl space, but it can cause a lot of problems. Our crawl space was terrible. From rotten floor joist and black mold, life can get real scary quick. The best thing you can do when you have moisture in the crawl space is encapsulation. No question. Don't take any chances. Moisture in your crawl space can cause you health problems and can cause your home to be condemned. Encapsulating your crawl space is an investment, but it's the right investment. This is what I came across that opened my eyes. https://crawlspacerepair.com/blog/Crawl ... y-Problems

That's what we did to solve the problem. We made sure we had all 3 mentioned my the experts. Vapor barrier, sump pump and a dehumidifier. We have 4 children, we have pets, you don't want to risk their health. And I know it's something people don't think about it. I didn't. I know some of it's common sense, but I never thought about it. How many times do you visit your crawl space? Once a year, once every few years? You just don't think about it.

If you have a crawl space that you haven't checked in a long time, go check it right now. If you have moisture problems, get it fixed. Don't wait. You risk your health, you risk your home if you ignore it. The problems only get worse.

The last month has been a nightmare. Literally. Having this work done is a big investment, but it's worth it. Thanks for allowing me the opportunity to warn others.

Our house was originally built in 1906. It's an old coal with many renovations. Our crawl space is 4 foot deep. Originally, it was 1 foot on the backend and 3 feet in the front where the furnace is. We live in Virginia where we get a lot of weather. My problem was rain water/snow melt. I also added a drain that keeps all the water out. That's something else you may want to consider.

This house means the world to our family. Our family has owned it since day one.

1. Check your crawl space right now
2. If you smell mold, rot or see moisture damage, fix it. Or get an expert.
3. Encapsulate your crawl space properly.
4. Use a sump pump and dehumidifier for best results.
5. Add a drain if needed

There's a lot of DIY sites and resources on YouTube if you need instructions.

Hope this helps.
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Re: moisture in crawl space - navigating my options

Postby janedavis on Tue Oct 08, 2019 3:11 am

kimma wrote:I have a home built in (very humid!) Atlanta in 1950, and expanded in 1970, so it's on two dirt crawl spaces. We're having issues with moisture in one specific area of the newer crawl that shows up after heavy rains - we notice because of a strong muddy smell (and sometimes a mildew-y smell follows that). We've gone under to look when the smell is there, and there is moisture that seems to be coming through the brick. We've never seen puddles of standing water, but there is mud splashed on the walls, so that suggests we may have had some puddles in the past. The ground on the outside of the house in that area is shady, and tends to hold moisture (there is moss growing there) but it slopes away from the house. We have gutters that we haven't always done a great job of keeping clear.

The older crawl does not have a vapor barrier at all, and is powder dry. The newer crawl has a 6 mil vapor barrier, but it doesn't cover all of the ground. There are vents for both crawls that are just open year round, covered with mesh - I don't think they can be closed. We have a new, expensive HVAC unit installed in the older crawl. There's no insulation under our house at all (sometimes I can see sunlight through the floorboards near the vents!), but I think that's a whole 'nother issue.

We've had 6 different companies come out to look, and each has a very different answer for us, at very different price points. I think we've got a consensus that this isn't a major foundation issue, and that while there is some mold and mildew in the crawl, that it's minor and isn't going to require any real remediation effort.

The options that are seeming the most sensible (er, cheapest) to us are to either:

option from contractor 1 - install a french drain to lead water away from the problem area, and then install a 6 mil vapor barrier in on the ground only in the crawl, and leave the brick uncovered. (cheapest quote)

option from contractor 2 - lay a thicker (12 mil) vapor barrier on the ground in the crawl, and run a thinner (10mil) vapor barrier up the brick, so that the entire crawl is covered up to the wood beams. (second cheapest quote)

But we've also had a contractor tell us we don't have a problem at all, one suggest we need a dehumidifier / air exchange system installed, one suggest we need total crawl space encapsulation, and one suggest we need $20k of foundation repair. No one seems to be on the same page about what to do! And I'm out of contractor referrals, and the internet is failing me.

Anyone dealt with this kind of thing, or know anything about it, or know where I could turn for advice?


In our case (the house was built in 1950, humidity issues) I just encapsulated mine over the last winter. Start to finish took about 3 months and I spent about $3000 to put in french drains and encapsulate. The crawl space at my home was about 1700 square feet and I have and average of about 4' of room between the ground and the bottom floor of the house.

The primary benefit we've noticed is smell. The house smells fresher all the time. Second, because we sealed the vents the air temperature in the crawl space has been about 10 degrees warmer (in the winter at least). I haven't calculated it, but it can't be hurting our heating and cooling costs in the rest of the house.
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