- Q.I’ve been
using wood I-joists for my floor framing. The designs have
called for 1x4 crush blocking inserted between the top and the
bottom 2x2 flanges and nailed directly to the OSB web.
I’ve also heard of using 2x4s nailed to the face of the
2x2s, instead of being inserted between them. Which way is
responds: It sounds like you’re confusing squash
blocks with web stiffeners. Squash blocks are blocks of wood
that are slightly taller than the depth of the joist. The
function of squash blocks is to transfer loads created by walls
and roofs above to a sill or wall plate below the I-joists.
Because these loads in effect bypass the I-joist, the squash
blocks also prevent "knifing" of the thin web into the top and
Web stiffeners are blocks of plywood or OSB that fit between
the flanges of an I-joist. These blocks are used at points of
support and are fastened with nails right up against the
I-joist web. However, web stiffeners are not fit tightly
between the top and bottom flange. Typically, a space is left
between the top of the stiffener and the underside of the top
flange. Web stiffeners reinforce the I-joist and prevent it
from buckling. Sometimes they are required as fillers so that
there is solid nailing for joist hangers.
Paul Fisette is
director of the Building Materials and Wood Technology program
at the University of Massachusetts in Amherst.