- 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.