What is a "Pier and Beam" foundation?

Pier and beam foundations are also know as raised foundation, block beam and perimeter beam.

Known as one of the first built and more sustainable foundation types, pier and beam/crawl space construction is still used today.  If your house is on a pier and beam foundation, you should have better access to the items under your house than a slab foundation allows. In contrast, a slab foundation has the plumbing buried under the house which are not accessible without digging under or breaking through the concrete.

For proper access, a crawl space door should be provided at the perimeter and should have a minimum of eighteen inches of head clearance and twenty-four inches of width.  There should be hinges and a latch to secure the door.  Preferably, the door will close tight, will swing to the side and not be in contact with the ground.  Doors that swing up have to be held in place for access.  In some cases, there is a removable portion of a floor, usually located in a closet, that can be removed so a person can access the crawl space.  The minimum opening for a drop down door should be twenty-four by twenty-four inches and there should be at least thirty inches below this area for the person to safely move from a standing to a crawling position.  The head clearance in a crawl space should be a minimum of eighteen inches from the ground level to the bottom of the floor joists. This provides access to areas of the house for inspection and repair. In most cases, the electrical wiring and plumbing is routed to all areas of the first floor from under the house and is secured by attachment to the bottom of the floor joists.

A crawl space should be ventilated to prevent accumulation of moisture which is damaging to the wood components as well as foundation movement and termite activity. The rule of thumb is to have evenly distributed vents around the perimeter of the building that allow a minimum of one square foot of ventilation per one hundred fifty square feet of crawl space surface area. In general, if you have a vent around the bottom of the house ever eight to ten feet, then you are probably fine. Often, homeowners will cover the ventilation openings in the perimeter to keep out the cold in the winter. This can be detrimental if the winter is damp. Decreasing the ventilation can prevent moisture from escaping the foundation crawl space and can cause damage. Some power ventilation systems can be designed to include a humidistat and baffles so that when the moisture is to high under the house, a fan turns on venting the moisture out. Once the moisture is vented out and the area under the house is dry, the fan turns off and the baffles close keeping out the cold. 

Your crawl space should be inspected annually for plumbing leaks, wood damage, pest access and any other problems. Always be careful when accessing a crawl space by wearing protective equipment like proper clothing and a respirator for proper health and safety.

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