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Q.Do laminated veneer lumber (LVL) and wood I-beams have a lower fire rating than conventional wood framing members? If so, have the model codes addressed this?

A.Individual LVL members or wood I-beams won’t resist fire as well as the solid wood members they replace. However, fire ratings are based on assemblies, not individual members. Several manufacturers of LVL and wood I-beams have obtained fire ratings on whole floor and ceiling assemblies by using their products with a Type X drywall facing the interior. For example, a one-hour fire-resistant ceiling assembly using TJI joists requires two layers of 1/2 inch Type X drywall applied to the bottom joist flange. A comparable one-hour assembly using solid-sawn joists requires one layer of 5/8 inch Type X drywall.

Since there are no "generic" wood I-beams (each is engineered to perform in specific ways) there is no generic assembly that achieves a certain fire rating. Each manufactured product and assembly must be approved after testing by a certified laboratory. Check with the manufacturer for each product you use. There are several small manufacturers whose volume does not justify the expense of obtaining a fire rating, and their products cannot be used where a fire rating is required.