The foundation walls, piers, posts, and wood-support framing in a crawl space should be inspected (as described in the section on the unfinished basement) for deterioration, structural deficiencies, and evidence of water seepage. Pay particular attention to the wood-framing members that are very vulnerable to decay and termite infestation. (See FIG. 11-13.)
Many homes, however, have crawl spaces that are inaccessible and cannot be inspected. These homes were built in accordance with the Federal Housing Administration (FHA) Minimum Property Standards, which permit the ground level to be 18 inches below the bottom of the floor joists and 12 inches below the bottom of the girders. Even if there is an access opening to the area (see FIG. 11-14), the clearance in the crawl space is too low for a person to maneuver around easily and perform a detailed inspection. However, you should look into the area from the access opening (using your flashlight) to discover any obvious problems or problem conditions.
In most parts of the country, the crawl space will be quite damp, even though there are no problems with water seepage. The dampness is the result of the capillary rise of ground moisture. Unlike a basement where the ground is usually covered with a concrete floor slab, the floor in a crawl space is often bare earth. Even though the soil might appear dry and dusty, moisture can be present. In some soils, the capillary rise is more than 11 feet above the water table.
Dampness associated with capillary moisture can be effectively reduced by covering the ground with a vapor barrier, such as 4- to 6-mil polyethylene. Roll roofing is also a good vapor barrier, but it tends to deteriorate from fungi. If you do not notice a vapor-barrier ground cover, you should consider its installation.
Fig. 11-13. Cracked and rotting wood-frame members in crawl space.
To help minimize the dampness, the crawl space must be ventilated. There should be at least two vent openings on opposite sides of the foundation with a total free area of 1 square foot for each 1,500 square feet of crawl space area, providing there is a ground cover. When no vapor barrier is used, there should be at least four vent openings (one on each side) with ten times the total free area. Look for vent openings. If you do not see any or they have been permanently blocked, put a note on your worksheet to that effect.
Crawl spaces are usually not heated. Consequently, unless there is some insulation between the floor joists, there will be heat loss between the heated room above and the unheated crawl area. Since moisture from the house can travel down through the floor, the insulation should have a vapor barrier on one side to reduce further moisture entry into the crawl space. The vapor barrier should be located above the insulation, facing the heated room (rather than below, facing the crawl area). If this vapor barrier is located below the insulation, the vapor will condense on its surface during cool weather. Depending on the amount of vapor, the resulting condensation buildup can reduce the effectiveness of the insulation. Look for insulation. You might find missing, loose, or hanging sections, which should be replaced or resecured. (See FIG. 1115.) If you find uninsulated heating ducts or pipes in the crawl space, record this fact on your worksheet as a reminder to insulate the exposed sections.
Some homes are constructed with both a basement and a crawl space. In this case, the crawl space need not be vented to the outside but can be vented to the basement. Look for evidence of water seepage in the crawl space. Even though there might be no signs of seepage in the basement, there might be some in the crawl area. I recently inspected a home that had a combination basement–crawl space. The basement had been painted, and there were no visible signs of a past water condition. The crawl space was separated from the basement by plywood doors that were painted on the basement side and looked good. However, when I inspected the crawl space, I found evidence of a previous water condition. Apparently, the back of the plywood doors (facing the crawl area) had not been painted over. There were water stains on the lower section. (See FIG. 11-16.)
While in the crawl space, check subflooring and support joists below kitchen and bathroom fixtures for evidence of decay and plumbing leaks.