Keep your home’s crawl space dry
No doubt; I live in a very humid place. From November to March we average almost seven inches of rain per month in Olympia, WA. This deluge can cause many homes to have standing water below them. A one-time event may not cause damage, but constant or recurring water “events” under your home can cause a lot of problems.
Standing water can cause moisture problems in the wood substructure. Wood rot and pest infestation are common results of damp under a home. Like all animals, wood destroying organisms (WDOs) need shelter, food, and water to survive. If they can find an available water source in their home, it often completes the list of needs for them to thrive. A common WDO here in Western Washington is the Anobiid beetle. This is a very destructive small insect and makes its home in wood with moisture contents between 14-20%. If there is standing water under a house, the wood in that access zone will probably be in that range. Other WDOs that are attracted to damp or rotting wood include: carpenter ants, damp wood termites, subterranean termites, wood rot fungi, and damp ants.
High humidity levels can also lead to mold growth and poor indoor air quality. Most mold species require high relative humidity or high moisture content to grow. At an indoor relative humidity (RH) of 60%, air enters the mold risk zone, which encourages mold growth. The wood arrives in this area with a moisture content of around 20%. Standing water under your home is likely to cause these levels in the floor joists, subfloors, and even the carpeting above.
The first question to answer is “is there a water problem under my house?” You can verify this 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 prevent water from coming back. I remember a problem I had with my first car. It malfunctioned shortly after purchasing it. My neighbor was an aspiring mechanic and offered to diagnose and fix it with me. “It’s the timing chain,” he proclaimed himself after a quick glance. We spent eleven hours in my parents’ garage in sub-zero temperatures changing it up. When all was said and done, the car still went bad and ran very poorly. My father came out and asked, “Did you check the distributor cap?” Replacing that five dollar part was all it took to get it running smoothly. Besides not letting my friend work on my car again, I learned a valuable lesson. Start with the simple and inexpensive things first when correcting or solving a problem. I like to mix this with another great axiom when solving a problem at home, going from the gross to the subtle. Fix the obvious stuff first, then move on to the more obscure stuff.
If the answer is “yes, there is water under my house”, you have a baseline of information, a starting point. Here are a series of suggested steps to keep the area dry in the future. I recommend doing these steps first, and then checking 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 prevent light from the vents from sprouting seeds in the soil. The recommended thickness is six mil. This plastic will help prevent soil moisture from moving into the basement air and into the wood substructure and house. It is a very important part of the moisture reduction effort.
Next, check your roof. Do all roof areas have adequate gutters that drain to 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 home’s water control system.
Check all gutter downspouts around the house. If they end up next to the house, extend them away from the foundation with backsplash blocks or undrilled pipe. Depending on the grade and slope next to the house, different measures will be needed to evacuate the water.
That leads to the next step. Check the slope and grade. You want the ground around the house to slope away from the foundation by a minimum of six feet to carry away the water. Adding soil around the foundation is the easiest way to accomplish this, but remember not to allow the siding to come closer than six inches to the ground. This air gap is recommended to allow the bottom edges of the siding to dry. If there is no room to add additional soil, a slough will need to be dug away from the foundation to allow for proper sloping.
Next, check the winds in the crawl area. Are they at ground level? Can the water flow towards them and enter the drag area? Many hardware stores have concrete pits designed to fit against the foundation to keep dirt away from these vents. Using these in some areas may allow you to add soil to create a slope without covering the vents.
With these simple measures, let it rain! She had a baseline from the last storm when there was water under her house. Check it again. If there is no water, congratulations! You probably have fixed the problem. Check back from time to time after heavy rains to make sure the crawl area stays dry whatever the weather.
If you find that there is still water under your house, it’s time to call a licensed drainage contractor. Explain what you have done to improve the drainage and ask what he recommends next. Whenever you hire a contractor, I recommend getting a referral from a friend or co-worker. Also, ask the contractor for references and call them to find out if the work they did fixed the problem and what it was like working with this person. You only want to pay for this service once.
A drainage contractor will assess the site for conditions that contribute to the water problem. Are there slopes on the foundation that throw large amounts of water against the house? Was the house built on a low spot? What are the types of soil? Where do the downspouts drain? The contractor may suggest measures such as new downspout drain lines, dry wells for downspout drains, sump pump drainage systems under the house, a drain curtain, etc. If the contractor is knowledgeable and does quality work, most water-related problems can be resolved.
