The gargantuan new General Motors
parts distribution center at Stead uses a
construction method that reduces maintenance
and energy costs.
The new GM parts distribution will
handle automotive replacement parts shipments
to more than 239 of its dealerships in
California, Nevada, Idaho and Utah, GM
officials said.
Clark and Sullivan Constructors of Reno
began building the massive 404,000-
square-foot warehouse facility in June 2002
and is expected to be finished by February.
The facility at 6565 Echo Ave., will house
384,000 feet of operating space and 20,000
feet of office space,
Its construction combines the traditional
form of tilt-up construction with an innovative
form of insulation built into the concrete
cladding of the walls.
The insulation is composed of 2-inch
pre-cut foam panels, or "sandwiches,"
embedded into two separate layers of concrete
to make the 12-inch thick concrete
walls. This differs dramatically from traditional
forms of tilt-up construction, where
7-inch concrete walls are erected, then insulated
with padded insulation and drywall as
the project nears completion
The extruded polystyrene foam panels,
which are produced by Dow Chemical and
are similar to other composite wall panels,
can have a R-value - the standard number
for measuring insulation efficiency - several
times that of traditional padding insulation,
reducing the amount of heat and energy
loss. Studies have shown that sandwiched
walls can have as much as an 80-degree difference
between its outside and internal
temperatures.
This is amplified by the use of 5-inch
vinyl polyurethane fasteners, which reduce
heat conduction better than their metal
predecessors and permanently bind the
panels to the sections of concrete.
Other advantages to building with a
sandwich panel system is that the exterior
wall doesn't have to be but it can be
painted or finished, and the thick concrete
of the interior wall is much more durable
than a sheet rock wall, which could be easily
damaged if, say, a forklift bumped into it.
The costs of building using this method
are high at first, notes Clark and Sullivan
Project Superintendent Ron Parks, but it
has both its short and long-run advantages.
"It costs more because you have to do
two separate [cement] pours," Parks said.
"But you can have several trades working on
the building at once, which increases the
turnaround rate."
In the first phase, after a perfectly flat
concrete base of the project has been
poured, a smooth 2 -inch layer of concrete
is poured into a 12-inch thick frame that
will be the wall panel. It is absolutely critical,
Parks said, that the pour be perfect
because it will be visible as the exterior of
the wall.
After the cement has been vibrated and
while it's still wet, the foam panel is fastened
using vinyl polyurethane connectors, which
go through the foam and into the concrete
leaving a peg on the top. The peg will fasten
to the final layer of concrete that will form
the back of the wall. Any doors or windows
are pre-cut and added into the wall's design.
The second phase begins after the concrete
has dried for a full 24 hours. At this
stage all fasteners, pick-up points, wire
mesh and supporting rebar are added much
in the style of traditional tilt-up models.
After everything is installed another 7 inches
of concrete is poured over the panels, creating
the back of the wall.
In the final phase a crane hoists the panels
using the pre-installed pick-up points
and sets them into pre-poured slots a couple
of inches deep. There the panels are fastened
to each other using traditional beams
and welding plates. Another stabilizing
pour is done around the walls and the roof
is added. The whole process in done on-site.
Parks added that warehouses using this
design are not prevalent, but he expects it to
take off. Clark and Sullivan Constructors
built the MSC Industrial Supply warehouse
in Fernley using a similar method, a project
that helped Clark and Sullivan win the GM
contract.
"There's no instruction booklet on how
to do this," Parks said of the new technology.
"You learn new things about it each time
you do it, sometimes by accident."
