The clients wanted me to transform the attic of their
70-year-old Arlington, Mass., home into a finished bedroom. The
attic, which until now had been used for storage, ran the
length and width of the house — 36 feet by 26 feet. There
were no knee walls; the rafters spanned from the ridge all the
way down to the eaves. The ridge was 9 feet 4 inches off the
floor, with collar ties 2 feet below the ridge. The clients
were hoping to get rid of the collar ties and add skylights to
create a more open living space.
Sounds simple enough, but there was a problem. In most cases
where the rafters meet the floor at the eaves, the floor joists
serve as ties, but in this house the rafters weren't tied to
the joists. In fact, the rafters sat on top of the attic deck,
so tying them to the joists wasn't a realistic option. Even if
it had been, a stairwell perpendicular to the joists would have
eliminated lateral support in the center of the house.
If we wanted to remove the collar ties, we would need to
install a structural ridge beam.
That created yet another problem. Our structural engineer
specified a ridge consisting of three 10-inch-deep LVLs placed
side by side. Not only would such a beam be hard to work with,
requiring that the three sections be drilled and bolted
together, but the end product would look so bulky in this
relatively small space as to nearly defeat the point of
creating an open ceiling.
New Product to the Rescue
To solve both problems, I decided to try something new. Not
long before, I had gotten an unsolicited mailing from Metwood
Building Solutions of Boones Mill, Va. (540/334-4294,
makes steel framing components, one of which — the
TruSpan beam — is a hollow rectangular beam made from
14-gauge cold-formed steel (see Figure 1). Its cross section
consists of two C-sections that have been welded together, with
steel reinforcing bar at each corner. By beefing up the
internal reinforcing (stepping up from No. 4 to No. 9 rebar,
for example), Metwood can increase a beam's carrying capacity
somewhat without making it bigger.
Figure 1. To keep the
depth of the structural ridge to a minimum, the author chose
Metwood TruSpan beams, which are made from cold-formed steel
with internal reinforcing bar welded on for extra strength. The
beams can be ordered with two-by nailers on top and bottom for
fastening to wood framing.
After reading the company's literature and talking with its
field rep, I decided that the TruSpan beams would be stronger,
lighter, more compact, and easier to install than comparable
LVLs or steel I-beams. The manufacturer's load calculations
showed that, in some cases, a 7 1/4-inch-deep TruSpan beam
could bear the same weight as a 16-inch-deep LVL. As for
weight, our ridge beam weighed about 22 pounds per lineal foot,
compared with 50 per lineal foot for a steel I-beam and even
more for an LVL. And the fact that you can buy it with 2-by
nailers on the top and bottom edges meant we could use normal
wood connectors for making attachments.
It seemed to be the solution we were looking for.
A Metwood engineer with a Massachusetts license specified the
beam's size and internal reinforcement. My engineer was not
familiar with the product, so he asked us to order a beam that
was somewhat stronger than Metwood's specs. Since this merely
required more internal reinforcement — rather than a
bigger beam — I agreed.
The ridge wasn't the only place we used this product. There
would be a French door at one end of the attic and a window at
the other, and we specified Metwood headers for both.
We would also need a supporting structure near the center of
the attic. That's because the ridge's weight and length
required us to order it in two sections, one 17 feet long and
the other 22 feet long. The joint where they met would need
some bearing beneath it, which we provided using a 4-foot-long
7 1/2-inch-deep Metwood beam supported at each end by
3-inch-diameter posts that straddled the stairwell. Fortunately
for us, there were bearing walls on either side of the
stairwell, so we didn't have to add posts below, a step that
would have made the job a lot more complicated.
The clients were concerned that this middle structure would
dominate an otherwise light and airy space, but that wasn't the
case. The header and posts were a smaller diameter than we
would have needed if we'd used wood, so there was less visual
Those of you quick with the math will notice that 17 feet and
22 feet add up to 39 feet, while the ridge itself is only 36
feet long. We cantilevered 3 feet of the 22-foot-long section
beyond the French-door gable end, and welded a 4-inch-by-4-inch
steel I-beam to it. The I-beam holds a hoist trolley, which the
owner can use to lift furniture three stories up from the
garden at the back of the house.
We had the most fun unloading the beams from a common carrier
truck, then getting them through the window into the attic.
Using ladders and boards, we created an angled slide from
ground level up to the window, then winched each beam up the
slide. Because we are a two-person crew, the homeowner and a
neighbor helped us get the beams through the window.
We had to trim a couple of inches off one of the beams, but it
wasn't difficult; we simply used an abrasive metal blade in the
circular saw (Figure 2). Since the 2x4 nailers don't count for
the beam's load capacity, we removed the top one so that the
beam would sit up higher off the floor. We left the bottom
flange so we could screw drywall to it.
Figure 2. The Metwood
beam can be cut easily with an abrasive blade on a chop saw
(left) and trimmed with a grinder (right).
We used a chain fall and ratchet straps to hoist the beams
close to the ridge, installed temporary collars underneath to
hold them, then used a hydraulic jack to seat them as tightly
against the peak as we dared (Figure 3). The rafters were not
all in the same plane — they weren't even the same exact
height — so we had to use shims in places, the biggest
gap being about 5/8 inch.
Figure 3. Temporary
collars supported the chain hoist and ratchet straps (top) used
to lift the beams as high as possible, where they were
supported from beneath with additional cross ties (middle). A
hydraulic jack (bottom) finished the job.
It's easy enough to drill into the metal beams with
self-tapping screws, which we did with the sheathing on the
outside of the headers in the end walls. Inside, we just
screwed the drywall to the wood nailer. We installed the three
skylights, creating some visually interesting shadows on the
ridge beam, which otherwise fades into the walls. The
electrician was easily able to drill through the Metwood beams
to run wires for the overhead lights and fan.
Because we were installing the steel headers in exterior walls,
we were concerned about thermal bridging. Fortunately, Metwood
informed us that we could order the beams with punch-outs every
couple of feet, which we did. Before hanging our drywall, we
used these punch-outs to fill the beams with expanding foam
insulation (Figure 4).
Figure 4. The Metwood
headers for the gable walls came with punch-outs that allowed
the author to insulate the cavities with spray
The cost for all the Metwood materials was about $3,200. An LVL
ridge beam and solid wood window and door headers would have
cost somewhat less, but would have taken more work to install.
Once I added in labor, the installed cost for each system was
Figure 5. With the ridge
in place, insulation (top) and drywall (center) were
straightforward. At last, home sweet teenage home
More important than cost, I believe we got a better job than we
could have with a conventional wood approach. The Metwood beams
let us open up and reframe this attic to make a very pleasant
bedroom (Figure 5). Adding knee walls a few feet in from the
eaves created a large storage area. The job was less work than
with wood, both because of the weight and the general ease of
installation. I wouldn't hesitate to use this product in the
future.Kipton Tewksbury is a
contractor in Arlington, Mass., and Brattleboro, Vt.