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Water in Crawl Space?

How to Take Care of the Problem of Water Under the House

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Water in Crawl Space Under Vapor Barrier

Water in Crawl Space Under Vapor Barrier

Copyright Lee Wallender; Licensed to About.com
Water in the crawl space: what fun! Instead of sinking your hard-earned money into something showy and sexy--something that you will actually see--such as kitchen counters or flooring, you get to sink it into water mitigation.

The procedure I am about to describe is very close to me, as I just paid several thousand dollars to have this done. For reasons I will outline later, I chose to mitigate this problem of water under the house by hiring a company rather than doing it myself. But that doesn't mean that you cannot do it yourself.

Main Problem: Standing Water in Crawlspace

I live in a very wet area, Seattle, Washington. So, under the house is a permanently wet area. After a hard rain, the wet area increases in diameter to about 10-12 feet. The ground, instead of merely being muddy and spongy, begins to pool up with water, about 1/2" deep.

During the dry months of June to October, the pool of water mainly dries up or percolates away--but it never completely goes away. Does any of this sound familiar to your situation?

Related Problem: Mold

With excessive water in the crawl space, you have the related problem of mold. Mold loves to grow in places that have: a.) Moisture; b.) Lack of light. Both conditions perfectly describe a crawlspace.

Mold will grow on the piers, joists, ducts, and other hard surfaces. But that's not all of the problem. Mold also grows on the "soft" materials, such as fiberglass insulation and on the plastic vapor barrier. When fiberglass insulation develops mold, it's impossible to clean off. Rip it out and replace it.

Process of Ridding Crawl Space of Water

There are many ways to get rid of the water. Before you even attempt what I am about to describe--water mitigation within the crawlspace perimeter--you'll want to first take care of all of those common basement waterproofing tactics.

The process described here basically sets up a perimeter within the crawlspace and seeks to capture the water trying to infiltrate the perimeter. When water hits this border, it is diverted into gravel-filled channels and fed by gravity to a sump pump. The sump pump then siphons up the water and purges it from the crawlspace. Let's look at it in closer detail:

  1. Protect: Unless you can access your crawl space from the exterior, you will need to bring in materials through the house and down an access door. You will need to protect all walk areas with plastic. Or, to prevent slipping, you can use builder's or rosin paper.
  2. Remove Vapor Barrier: Your crawl space may already have a plastic vapor barrier. Remove this and discard.
  3. Dig Trench: Dig trench around entire interior foundation, using foundation as a guide. Trench should be between 8" and 24" from the foundation. If not, it may undermine the foundation.
  4. Lay Pipe: Lay down 3" socked flex perforated pipe through entire perimeter trench.
  5. Cover with Gravel: Cover with 1 1/2" drain rock.
  6. Spread Soil: What to do with all of that dug-up soil? Spread it evenly around crawl space.
  7. Install GFCI: Install a GFCI outlet in crawlspace.
  8. Install Sump Pump: At the low end of the perimeter trench, install a sump pump as recommended by manufacturer's directions.
  9. Discharge to Exterior: Sump pump to discharge perimeter trench water to outside.
  10. Install Vapor Barrier: Install 6 mil vapor barrier to prevent vapor transfer to crawlspace.

Hire a Company or DIY?

It's hard work, especially if your crawl space is very low. Mine was between 4'6" and 5', which is pretty good. Even then, you have hundreds of pounds of drain rock and hundreds of feet of perforated pipe to move through the house. If you're not adept at electrical work, installing the GFCI can present a learning curve, too.

Not an impossible DIY task, but you'll want to think long and hard before you take it on yourself.

Cost to Get Rid of Water in Crawl Space

Of course, the cost differs according to where you live and the size of your house (and the size of your problem; bigger or even multiple sump pumps may be needed).

My house required 170' of perforated pipe and a single Zoeller 1/3 HP sump pump. I'd say it was a fairly average installation. Cost to hire a company, all materials and labor included (Fall 2009): $3,600.

Once again, this is Seattle, Washington, and I cannot imagine that wherever you live gets more water than we do.

Note for Seattle residents: Every week, I get another message from a reader asking the name of the company. It was PermaDry, and they did an adequate job.

But Do You Need to Get Rid of That Water Under the House?

Water mitigation and mold remediation companies will not agree with me. But in reality, you do have some leeway when it comes to water in the crawl space. Water can sit in the crawl space for a long time without having any immediate adverse effect on your house.

However, this lack of urgency is also one of the worst aspects of this problem: it is far too easy to let the problem fester over the years until it has become unmanageable. In the short term, you're just dealing with mold on the hard surfaces and perhaps some insulation needs to be removed and replaced. But over the long term, you're in for trouble: standing crawl space water can damage the house's foundation; the wooden beams and joists can begin to rot away; and harmful strains of mold can develop.

So, even though it is painful and doesn't seem to be a "red flag" issue at the moment, it is best to mitigate the water problem as early as possible. At the very least, you will be required to dry up the crawl space when it comes time to sell your house.

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