As a structural engineer, I get a steady stream of calls from
remodeling contractors looking for ways to remove bearing walls
and posts, either to enlarge a space or to create more
One such call came from the owners of the 1960s-era ranch shown
here, which sat on a sloping lot with a full basement. The
home's construction was pretty typical: The 26-foot-long main
girder in the basement ceiling was supported by two
intermediate posts spaced about 8 feet apart. Our plan was to
create a new 16-by-20-foot home theater and play area by
removing one of the posts. But first I needed a way to
reinforce or replace the existing four-member 2x10 girder that
supported not only the first-floor joists but also a bearing
wall that carried attic joists used for light storage (see
Figure 1. The plan called for opening up
this basement space by removing a steel post, but first the
massive built-up girder had to be reinforced to carry the new
span. Temporary support walls were set far enough back to allow
plenty of working room.
The most obvious option — installing an engineered lumber
or steel undergirder — wouldn't work, because at 7 feet 8
inches the basement ceiling wasn't high enough. Also, a quick
calculation revealed that with only 9 1/4 inches of depth (2x10
floor joists) to work with, even the strongest engineered
lumber wasn't beefy enough to function as a flush beam.
Steel solution. We could have used an 8-inch
wide-flange I-beam, but the labor and shoring necessary to
support both the first floor and the attic during construction
replacement would have been costly and disruptive to the
Instead, I looked for a different steel member that might be
easier to install. I was originally thinking of a "C" shape
when I started browsing the Steel Construction Manual (American
Institute of Steel Construction,
www.aisc.org), the best
resource for steel design. Paging through, I remembered that a
traditional I-beam could be cut down the center of the web,
creating two T-shaped pieces of steel called wide-flange tees,
or WTs. Thinking about the project at hand, I realized an
important advantage of this approach: The WTs could support
both the joists and the existing beam, which would eliminate
the need to through-bolt the steel and built-up 2x10 girder
(see illustration, below).
There are no capacity tables for WT members in the beam section
of the steel manual — as there are for the common
structural-steel shapes — so designers have to use the
shear, bending, and deflection tables to figure out the design
calculations. After doing the math, I concluded that a pair of
WT8x13 steel beams, made from a W16x26, could handle the load
and would be relatively easy to install.
Making a WT Beam
The way that WT members are made — slitting a wide-flange
I-beam down the center to produce two equal-sized sections
— releases stresses in the steel, which can cause a
My local welding shop cut a 20-foot-long W16x26 — a
common beam size — into a pair of WT8x13s over the course
of a day and a half, allowing the steel to rest between cuts in
an attempt to reduce the camber. When the cuts were complete,
the camber was in the correct direction and limited to about
3/4 inch. I figured the slight arch would reduce the dead-load
sag created by the longer span.
A couple of days before the steel was delivered to the site,
the contractor built two temporary walls to support the joists
during beam placement. Each stud wall was placed 36 inches off
the beam centerline, providing a 6-foot working space. The
existing beam was strong enough to temporarily support the wall
and attic joists above without the post, but to be safe we had
the homeowner temporarily remove the items stored in the
With the floor system supported, the contractor cut a 3/4-inch
channel between the joist ends and the beam, using a recip saw
fitted with a demolition blade. Since the beam was only 8
inches tall, the top inch and a half of the 2x10s was left
intact (Figure 2).
Figure 2. After temporarily supporting the
floor, the crew cut the joist ends away from the girder,
creating a channel for the two T-shaped steel beams to slip
Preparing the Steel
The two crew members on site used four-wheel dollies to move
the beams, which weighed 210 pounds apiece (Figure 3). Each
piece of steel would bear on the existing sill plate at one end
and on a triple 2x4 post on the other. The stud post would
replace the existing steel column and form part of a new
Figure 3. At about 200 pounds each, the
T-shaped pieces of steel were light by structural steel
standards. A pair of four-wheel dollies (top) and a drywall
lift (bottom) made the job easier.
Before we could place the steel, we had to notch the exterior
sill plate to make room for the flange (Figure 4). But because
we couldn't easily notch the part of the sill underneath the
existing 2x10 girder, we also had to notch the WT flange on one
side of the web, which the steel fabricator did on site with a
Figure 4. The mudsill was notched (top) so
the joist ends would rest on the top of the outer flange of
each WT beam (middle). Since removing material from under the
existing girder would have been difficult, one side of the WT
flanges was cut away instead (bottom).
Given that the flanges of a beam carry the bending forces, you
might wonder how we could remove part of an I-beam's flange
without sacrificing the beam's strength. Maximum bending stress
in a simple-span beam (one with a support at each end and no
intermediate supports) occurs at the center of the span —
which is why you should never notch the top or bottom of a beam
near the center of the span.
But at the ends of a beam, bending stress is zero, which makes
it possible to trim the flanges of a steel beam — or
notch a lumber joist — near the bearing points. (Again,
this assumes a simple span. For continuous beams — those
that span intermediate supports — or cantilevered beams,
the shear and bending stresses are much more complicated, and
cuts and notches should be avoided.)
Before cutting away the flange, I also needed to check that
there would be enough of it left to spread the bearing over a
sufficient area, so that the wood plate wouldn't be crushed.
After cutting it, we would be left with a 3-inch-by-5-inch
bearing area, or 15 square inches.
On this project, we had SPF mudsills, which are rated for a
maximum compressive force of 425 pounds per square inch; that
means the 15 square inches of flange material would be able to
transfer a load of 6,375 pounds (15 square inches x 425 pounds
per square inch) before crushing the wood fibers.
Since there were two WT beams, this was plenty of
Placing the Steel
The steel was set on a drywall lift and hoisted into place a
piece at a time. We marked and cut the wood post and secured it
to the beam with Simpson A23 angles and self-drilling screws.
We used Tapcons, driven at an angle, to attach it to the floor.
The post would ultimately become part of a partition wall, so
the connections were simply meant to prevent accidental bumps
from dislodging it during the rest of the construction.
Installation of the beams took about six hours, including
temporary shoring, cutting the joists, installing the steel,
and removing the shoring. After the work was completed, I
walked around the living area upstairs but couldn't detect any
noticeable bounce where the post had been removed. On paper,
anyway, the floor was less stiff — but that wasn't
evident when walking around. And without a post in the way, the
clients appreciate the new room below (Figure 5).
Figure 5. The completed space provides an
unobstructed view of the 10-foot movie screen housed in the
Jordan Truesdell, P.E., is a structural
engineer in Blacksburg, Va.