subject: Post And Beam Foundations [print this page] Whatever terminology is used, this type of foundation can be found in many parts of the country. Instead of the continuous support provided by a basement or crawl space foundation, a post-and-beam foundation provides many points of support. Wood posts typically extend from separate concrete footings to beams or girders that are connected to the first flooring framing.
Posts are spaced at standard intervals around the perimeter of the building and at intermediate points beneath the building. There are numerous variations of this foundation. Sometimes pressure-treated wood posts extend directly into the ground. In other situations, the "posts" are not wood but masonry - concrete that has been poured into tubular cardboard forms, or bricks or concrete blocks laid up on a footing. In these last three examples, beams and/or floor framing rest on top of each masonry pillar.
Like any foundation, post-and-beam has advantages and limitations. Builders and homeowners often opt for this foundation because it's quick and inexpensive to erect. Minimal excavation and very little concrete are required. The post-and-beam structure elevates the house above ground level to provide protection against moisture and insect damage. In coastal areas, taller posts keep buildings above the storm surge. Builders often finish off these foundations with some sort of skirting treatment, covering perimeter posts with wood siding or similar material.
Of course, there are problems with post-and-beam or post-and-pier foundations. Each post is supported independently, so if one post or footing fails, the building will sag in that area. This is a common occurrence in older houses that were built with undersized posts or inadequate footings. Posts that are close to ground level or in contact with the ground are prone to decay if they are not pressure-treated with wood preservative.
But the biggest problems with a post-and-beam foundation have to do with bracing and anchoring the foundation so that it doesn't rack or shift out of position. High winds, expansive soil and seismic activity are natural occurrences that can topple a building off a weak post-and-beam foundation.
To prevent problems with post-and-beam foundations, skilled foundation repair contractors use a variety of techniques. Inadequate footings are replaced with sound footings. Rotted and undersized posts are replaced. Foundation repair specialists use engineered steel framing connectors to anchor posts to the building's floor framing and to the foundation footing. These connectors are often referred to as hold-downs or hold-down hardware.
To improve a post-and-beam foundation's racking resistance, new diagonal braces can be installed, or shear walls can be constructed by linking a line of posts with framing and sheathing. In some cases, a line of posts beneath a building's outside wall can be replaced by a masonry stem wall that's formed on top of a continuous footing.
If you live in a house with a post-and-beam foundation or are considering purchasing such a house, it's wise to have an experienced foundation repair contractor evaluate the foundation to make sure the house is structurally sound.
