Floor joists support the floor you walk on and keep floors flat and rigid in homes built with basements and crawl spaces, as well as all second story floors. There are no floor joists in the first story of homes built on slabs. A design change that can save you money in both new construction and remodels is to use taller floor joists to save the costs of girders and posts. Girders and posts are required to support floor joists if the span they are covering is longer than their strength can support. To span these long distances (6 feet for joists that are 6 inches thick) a girder that runs perpendicular to the joists is placed under them and is supported by a post to the basement floor or a footing in the ground with a crawl space. The cost for a girder and post can become expensive, especially in a home with a crawl space. An alternative that can save you money is to use taller floor joists — even 2 inches taller will allow a joist to span a few more feet. So consider the cost of the taller joists compared to shorter ones, versus a girder, post and footing. This could save you hundreds or even thousands of dollars when you remodel or build a home.

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