Out of sight, Out of Mind– In my 18 years of inspecting homes for customers, the majority of major structural problems that I find are in the crawlspace. Almost all of these major problems could have been avoided with a regular crawlspace visit to detect moisture, condensation, and standing water. Water and moisture related problems account for the majority of major defects found in homes I inspect.
How does water get into a crawlspace?
Primarily, water gets into crawlspaces in one of the following ways:
- through masonry foundation walls
- from poor grading and drainage at the exterior of the home, where the soil at the exterior grade slopes towards the foundation rather than away from it
- from low areas that hold water next to the foundation
How can this be prevented? One way is by maintaining positive drainage (where the soil slopes away from the foundation) around the perimeter of the home.
In special situations, such as when a house is built on a steep hill or slope, it may not be possible to have positive drainage. That is when waterproofing becomes necessary. Waterproofing involves sealing the exterior foundation wall below the grade with a waterproof sealant, then installing a French Drain System around the perimeter of the foundation to transport water away from the foundation wall.
Water also gets into crawlspaces from plumbing leaks, both from drains and from service lines. To inspect the drains, the insulation must be pulled back from around the drain lines in the crawlspace to look for water stains on the plywood flooring. If the service lines are leaking, it will be readily visible as the lines are under pressure. The water will be obvious to anyone making a complete journey through the crawlspace as it will be spraying or dripping, thus causing a puddle below (this is usually audible as well as visual).
Another way water gets into a crawlspace, and often overlooked in home inspections in Raleigh, NC, is in the form of condensation due to poor ventilation in the crawlspace area. Crawlspace vents should have operable flaps, and they should be open all year round with the exception of periods of hard freeze when the vents are closed to protect the plumbing service lines from freezing and bursting. If a crawlspace is not adequately ventilated, beads of moisture form on the insulation and exposed wood floor members. The moisture on the wood promotes fungus and mildew growth, both of which will, given time, weaken and destroy the wood. A plastic vapor barrier laid on about 80% of the dirt floor of the crawlspace will cut down on the need for ventilation and can relieve and help correct a minor ventilation problem.
Water penetration into a crawlspace is also common around exterior doors,and behind synthetic stucco. It’s important to maintain the caulking around all exterior door openings. On older homes, the area where a wood deck attaches to a house is a common place for wood damage to occur. On new homes, proper flashing should prevent this, although periodic inspections to the band joist are advisable. On homes without a protected covered entryway, it’s not unusual to find the band joist water damaged from lack of flashing or from improper sealing at the exterior. Proper caulking of doorframes and weather stripping are important.
The crawlspace area should be inspected at least four times a year for any signs of water penetration and moisture problems. The exposed wood floor members should be dry and clear. Little grayish-green nodules on the wood that smear when rubbed are a fungus that is living on moisture in the wood and are a sign of a moist crawlspace. Humpback cricket colonies are also a sign of too much moisture in the crawlspace. Contracting with a pest control company yearly is also wise.
Jon Supler is the president of Residential Construction Company in Raleigh, NC. He is a licensed NC contractor and home inspector. He has 18 years home construction and building management experience along with 18 years of home inspection experience. In addition, Jon provides synthetic stucco water intrusion inspections. Please visit his website at www.jonsupler.com for further information.