Q: Several years ago when I purchased my home I had the home inspected by a professional home inspector. Now that I'm moving on the buyer had the home inspected by a different person. The second inspector said that the floor joists in the crawl space were too short and did not overlap one another. The floor joists are manufactured wood called I-joists. Do they need to overlap like regular wood joists?
A: I've been framing and building for many years and have used both types of floor joists. When we used standard wood joists, fir or pine lumber, we would overlap the joists by 3 inches and nail the joists to the sill plate and to each other to keep them standing upright until the subfloor could be installed. Over time, a long wooden floor joist can sag, which can cause the ends of the joist to tip up where it sits on the sill plate. This can cause the finished floor above the lap joint to crack or the movement can crack wallboard above. I have inspected standard wood joists that did not overlap at the beam, but on closer inspection, I found that the sheets of 4 by 8-foot subflooring were spaced so the joint of the subflooring was 3 or more inches from where the joists meet end to end. This meets the 3-inch overlap requirement. This is something you do not have to worry about with a manufactured wood I-joist. I-joists can be ordered and designed for each application, or a stock size, usually 16 to 18 feet long, can be cut on-site to fit different applications. A standard I-joist is normally 8 feet to 24 feet in length, but I have seen much longer I-joists. With longer I-joists, a center support beam or header will be needed to prevent "bouncing" floors. If the builder or architect specified the I-joists to be joined end-to-end, then there really is no need to overlap the I-joists for stability. The home inspector needs to ask questions of a professional, as I sometimes do, before making a judgment on an installation that's questionable. Mistakes like this can be costly for the homeowner.
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C. Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at C. Dwight Barnett, Evansville Courier & Press, P.O. Box 268, Evansville, Ind. 47702 or e-mail him at dbarnett4539@gmail.com.
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