Though it's initially more
expensive than wood framing,
steel will save you money by eliminating many callbacks
by Jeff Loughead
We'd been building wood-framed houses for more than two
decades, but seven years ago, we decided it was time to make
the move to light-gauge steel framing. The quality of the
lumber we'd been getting was just terrible. At one point, we
found that we were only using a little more than a third of
every truckload of lumber, and the price was going through the
roof.
I had read about the advantages of steel, but with no
practical experience of our own, we were anxious about making
such a big change. We discussed it with several local steel
suppliers, and got a lot of help from one sales rep who was
willing to spend time training us.
At the time, we thought lumber prices were just going to keep
going up. As it turned out, things started to stabilize within
a couple of years, but by that time we were using nothing but
steel and could see the advantages for ourselves. Now we
wouldn't think of going back.
Preconstruction Benefits
It's a lot easier to do takeoffs and bids on steel-framed
jobs, because steel suppliers will hold a price for 30 days or
more, and their prices usually go up only once a quarter. If
you're using wood, most suppliers won't guarantee a price for
more than a week, two at the most. If it takes the client a
month and a half to get back to me, I've got to have language
in the contract that says the price is subject to change if
lumber prices go up. But on a steel job, I can pull up the list
from a job I did last month, reference it for the takeoff I'm
doing today, and get an accurate price out there a lot
sooner.
Waste not, want not.
We also
save time because the material itself is so consistent. Every
stud is perfectly straight, so I don't even have to go meet the
trucks at the drop site. Everything but the headers comes
precut - if you need 9 foot 6 inch studs, that's what you
order. All the framing waste from an 1,800-square-foot house
fits into one 32-gallon trash can. Instead of paying someone to
haul it away, I just drop it off at a local metal scrap
yard.
Labor
When I first started looking at steel, I thought I could just
go down the street and hire some of the commercial guys who
were finishing a big supermarket. But there's a big difference:
In most commercial jobs, the building is held up with
structural steel, and the light-gauge stuff is only used for
partitions. We found that the commercial guys had the basic
skills, but they didn't know anything about load-bearing
walls.
Square one.
At first, I had
to snap and measure the layout for each wall myself. I'd take a
sharpie pen and mark the rough openings with a K for a king
stud and a T for a trimmer. But most of the commercial guys
caught on pretty quickly.
In fact, we found that it was easier to convert the commercial
guys to residential steel than it was to retrain carpenters to
work with steel. Steel framers are already used to working with
the material, and know how to use screw guns and chop saws.
Steel either fits or it doesn't, and if it doesn't you've got
to unscrew it and fix the problem. Steel guys know that, but
it's an adjustment for wood framers, who are used to hammering
on things until they fit. Some of our wood framers did make the
switch to steel, and the guys who wanted to stick with wood now
frame our I-joist floors and truss roofs.
Design and Construction
Our first project was a tract of 46 houses. The first unit
took us nearly three weeks to frame, when it should have taken
less than a week. There's no way to avoid taking an initial hit
when you make the switch - but if you plan ahead, you can make
it a lot less painful.
Engineering.
Framing with
steel is slower than working with wood. That increases your
costs, so if you don't compensate by using the material
efficiently, you're in trouble. That means having an engineer
gauge the material and design the header systems from the
ground up, rather than taking a set of wood-frame plans and
converting them.
When we started out, there were no prescriptive tables for
light-gauge steel. It's easier now, because the engineer can
reference the charts and come up with the specs in a lot less
time. Steel is stronger than wood, so the studs can easily go
24 inches on-center. Our joists and roof trusses use the same
layout spacing so all the loads line up and transfer right into
the foundation.
Division of Labor
Although all of our bearing walls and partitions are framed
with steel, we use wood I-joists in our floors. Like steel,
they're straight and consistent, but we think they provide a
nicer floor. When you jump on them, they produce a satisfying
"thud," rather than the disconcerting "boing" of a floor
supported by steel joists.
Because we have separate wood and steel crews, we work on two
houses at once. The steel crew finishes framing the first-floor
walls, then the wood crew moves in and installs the floor
joists and subfloor. By the time they're done, the steel crew
has the first-floor walls of the next unit ready.
Work smart.
When a carpenter
grabs a piece of material on a wood-framed job, all he has to
do is get the right dimension. But a steel framer has to choose
between 18-gauge material for a bearing wall, and 20-gauge for
a partition. We order materials on a per-home basis, so if the
framers use material from the wrong pile, they're going to come
up short somewhere.
All the walls are built in place, rather than assembled on the
deck. Once we've bolted the bottom track to the slab, we brace
the corners in position, run string lines across the top to
check for level, and screw the top track in place.
Headers.
Next, we fill in
the remaining studs, and header off the rough openings (Figure
1). This is a critical area, because every header has to be
made up on site as specified by the engineer (). On some jobs,
there might be six different header types and gauges, although
we can usually reduce that number by using heavier headers than
we need for some openings. This wastes a little material, but
it simplifies things and saves time. Another difference between
wood and steel is that steel headers are attached to the top
track, with cripples extending down to the opening, rather than
sitting at the top of the opening with cripples extending up to
the top plate, as in a wood frame (Figure 3).
| | Figure 1.In steel framing,
walls go up piece by piece, rather than being
preassembled on the deck. Self-locking clamps hold the
studs in position while the framer drives screws
through the side flanges of the top and bottom tracks -
the steel equivalent of the top and bottom plates - and
into the studs. |
| | Figure 3.Cripples extend
downward from the header beneath the top plate, and
terminate at the rough opening. |
Quality framing starts with accurate material.
Steel won't warp or twist, but that doesn't help if the
material isn't correctly sized to begin with. Cross-sectional
dimensions and gauge are always consistent, but unless your
supplier cuts the material to length accurately, you're in
trouble. There's no problem with studs that are 1/8 inch long
or so, but if the variance is much more than that the material
has to be recut. Because steel framing is labor-intensive to
begin with, this isn't something you can afford. Studs that are
too short will fit, but they're a structural problem because a
short stud is just hanging from the screws. That's not so bad
in a partition, but in a bearing wall the studs must butt
tightly against the top and bottom tracks.