Crawl Spaces

In short, most problems throughout crawl spaces in Oregon are the result of excessive moisture or a lack of proper ventilation.

A crawl space is typically defined as any void space beneath a heated living space that has a bare dirt floor. In most cases, crawl spaces are surrounded by a perimeter concrete foundation and have some point of access, either from the exterior of the space or from a hatch in the floor of the living space above.

Crawl spaces are an efficient way to construct living space but have a certain number of common construction practices that must be followed to ensure good long term performance. The following are common problems found in or around crawl spaces that often result in problems:

Lack of Access: If you can’t get in, you can’t discover damage or perform repairs. A crawl space should have an adequate access hatch and clear working space beneath the floor framing. An access hatch should be at least 16″ X 24″ and have no pipes, electrical cables or other items routed across it. Once inside, there should be a bare minimum of 18″ of clearance beneath any floor framing to allow movement throughout the space. Additional clearance is necessary around all heating ducts, plumbing pipes and other mechanical lines to allow access to all portions of the crawl space. Crawl spaces that lack this access often require extensive work when a home is sold as they are typically not able to be financed by many lenders.

Inadequate Ventilation: In Oregon, most wood destroying insects and rot fungi flourish in a moist environment. All crawl spaces must have properly sized and placed vents around the perimeter to allow air to flow throughout the space. Additionally, the area in front of the vent openings must be kept clear of dirt, leaves and other items and must be covered by screens to keep rodents and other pests out.

Missing or Improperly Installed Vapor Barrier: A 6 mil black plastic vapor barrier must be properly installed over any bare soil in a crawl space to prevent moisture inherent to the ground from seeping into and lingering throughout the crawl space. A properly installed vapor barrier is overlapped at least 12″ at any seams and has no rips, tears or other inconsistencies. Missing or improperly installed vapor barriers are often the cause of insect damage, wood rot and other problems.

Debris: Wood scraps and other debris provide food and habitat for insects and rodents and should be removed from a crawl space, if present. In general, any items that can be gathered with a standard garden rake should be removed.

Animal Droppings: It’s very common for raccoons, possums, cats, rats and other rodents to access crawl spaces through missing or damaged vent screen openings. Once inside, these animals often damage the under floor insulation and heating ducts, and leave droppings and carcasses throughout the space. In addition to the damage to the building being corrected, the droppings and carcasses are a health hazard to people working in the space and should be removed. Additionally, it is often necessary to replace part or the entire contaminated vapor barrier throughout a crawl space after animal activity.

Water/Moisture: Keeping the moisture level in a crawl space to a minimum is a very important step in preventing damage from wood destroying insects and wood rot. All surfaces around the perimeter of the house should slope away to prevent water from collecting near the structure. Additionally, all roof runoff should be routed into storm drains or otherwise away from the house to prevent water from collecting near the building.