Keep Your Home’s Crawl Space Dry

Posted by on Sep 26, 2011 in Maintenance Tips | 3 comments

Keep Your Home’s Crawl Space Dry

There is no doubt; I live in a very wet place. From November to March we get an average of nearly seven inches of rain a month in Olympia, WA. This deluge can lead to many homes having standing water under them. A one-time event may not do damage, but constant or re-occurring water “events” under your home can cause a lot of problems.

Standing water can lead to moisture issues in the wood sub-structure. Wood rot and pest infestation are common results of moisture under a home. Like all animals, wood-destroying organisms (WDO’s) need shelter, food and water to survive. If they can find a ready source of water in your home it often completes the list of needs for them to thrive. One common WDO here in Western Washington is the Anobiid beetle. This is a very destructive little insect and makes its home in wood with moisture contents between 14-20%. If there is standing water under a home, the wood in that crawl area will likely be in that range. Other WDO’s that are attracted to moist or rotting wood include: carpenter ants, dampwood termites, subterranean termites, wood rot fungus and moisture ants.

High moisture levels can also lead to mold production and poor indoor air quality. Most mold species require high relative humidity or moisture content to grow. At 60% indoor relative humidity (RH) air enters the mold-formation risk zone, which is conducive to mold growth. Wood reaches this zone at about 20% moisture content. Standing water under your home may likely produce these levels in floor joist, sub-floors and even carpets above.

The first question to answer is “is there a water issue under my home?” You can check this out yourself, or hire someone to do a maintenance inspection of your home.

If there is a water issue, I recommend following a logical progression of changes that will dry out that area and keep the water from returning. I am reminded of a problem I had with my first car. It ran rough shortly after buying it. My neighbor was an aspiring mechanic and offered to diagnose and fix it with me. “It’s the timing chain,” he proclaimed after a quick look. We spent eleven hours in my parent’s garage in freezing temperatures changing it. When all was said and done, the car still backfired and ran very poorly. My father came out and asked, “Did you check the distributor cap?” Replacing that five-dollar part was all that was needed to have it running smoothly. Besides never letting my friend work on my car again, I learned a valuable lesson. Start with the simple, inexpensive things first when correcting or fixing a problem. I like to mix this with another great axiom when solving a house problem, go from gross to subtle. Fix the obvious things first, then move to the more obscure.

If the answer is “yes, there is water under my home”, you have a baseline of information, a starting point. Here is a series of suggested steps to keep the area dry in the future. I recommend doing these steps first and then check to see what results were achieved after the next big rain.

First, make sure there is a plastic vapor barrier covering all the dirt under your home. Preferably, black plastic to keep the light from vents from sprouting seeds in the soil. The recommended thickness is six mil. This plastic will help to keep moisture in the soil from moving up into the crawl space air and into the wood sub-structure and the home. It is a very important part of the moisture lowering effort.

Next, check your roof. Do all roof areas have proper gutters that drain into downspouts? If gutters are missing or damaged, have a licensed gutter contractor install new ones. They are relatively inexpensive and an important component of your homes water control system.

Check all the gutter downspouts around the home. If they end next to the home, extend them out away from the foundation with splash blocks or non-perforated pipes. Depending on the grade and slope next to the home different measures will be needed to get the water away.

That leads to the next step. Check the slope and grade. You want the soil around the home to slope away from the foundation for a minimum of six feet to carry water away. Adding soil around the foundation is the easiest way to achieve this but remember not to allow the siding to be closer than six inches from the soil. That air space is recommended to allow the bottom edges of the siding to dry out. If there is not room to add additional soil a swale will need to be dug out away from the foundation to allow for the proper slope.

Next check the crawl area vents. Are they level with the ground? Can water flow into them and enter the crawl area? Many hardware stores carry concrete wells designed to fit up against the foundation and hold soil back away from these vents. Using these in some areas may allow you to add soil to create slope with out covering the vents.

With these simple measures in place, let it rain! You had a base line from the last storm when there was water under your home. Check it again. If there is no water, congratulations! You have likely fixed the problem. Check it again from to time to time after big rain events to verify that the crawl area stays dry regardless of the weather.

If you find that there is still water under you home it is time to call a licensed drainage contractor. Explain to him or her what you have done to improve the drainage and ask what they recommend next. Whenever hiring a contractor I recommend getting a referral from a friend or co-worker. Additionally, ask the contractor for references and call them to find out if the problem was fixed by the work performed and what it was like to work with this person. You only want to pay for this service once.

A drainage contractor will evaluate the site for conditions contributing to the water problem. Are there slopes above the foundation that shed large amounts of water down against the home? Was the home built in a low spot? What are the soil types? Where do the downspouts drain? The contractor may suggest measures such as new downspout drain lines, dry wells for down spout drains, sump pump drain systems under the home, a curtain drain, etc. If the contractor is knowledgeable and performs quality work most water issues can be solved.

For more information about Home Inspections contact Sound Choice Inspections Inc. (360) 561-0951

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