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Chapter 17 Constructing Structures
walls. Most foam sheets have a reflective
backing to improve the insulation value of
the sheet. Most homes constructed today
have a layer of plastic over the sheathing to
prevent air from leaking in.
Normally, the roof is put in place
before the utilities are installed. See
Figure 17-18. The actual roof surface
has two parts. Plywood or wafer-board
sheathing is applied over the rafters.
Builder’s felt is often applied over the
roof sheathing. Wood or fiberglass shin-
gles, clay tiles, or metal roofings are then
installed over the sheathing and felt. Flat
and shed roofs often use a built-up roof.
A built-up roof starts with laying down
sheets of insulation. Roofing felt is laid
down, followed by a coat of tar, which is
covered with gravel.
On many structures, the overhang of
the roof is also finished. A fascia board is
used to finish the ends of the rafters and the
overhang. The soffit is installed to enclose
the underside of the overhang. Soffits can
be made of aluminum, vinyl, or plywood.
They must have ventilation holes or vents
to prevent moisture and heat buildup in
the attic.
Once the sheathing and roof are
installed, the openings for doors and win-
dows are cut out. The doors and windows
are then set in place. Now the house is
secure and weather tight.
Installing Utilities
Normally, the utilities are installed after
the building has been enclosed. This pre-
vents theft and damage from the weather.
Some parts of the utilities are installed ear-
lier, such as large plumbing lines. The util-
ity system includes four major systems:
Electrical.
Plumbing.
Climate control.
Communications.
Electrical systems
The electrical system delivers elec-
trical power to the different rooms of the
home. The power is brought into the house
through wires to a meter and distribution
panel. This panel splits the power into
110-volt and 220-volt circuits. Each circuit
has a circuit breaker to protect against cur-
rent overloads.
Appliances such as clothes dryers,
electric ranges, water heaters, and air con-
ditioners require 220-volt power. Circuits
for smaller appliances, lighting, and wall
outlets use 110 volts. Outlets might have
power fed to them at all times. Switches
can also control outlets. Figure 17-19 shows
a 110-volt circuit with wall (duplex) outlets
and a ceiling light. The outlets always have
power. The circuit to the light has a switch,
however.
Figure 17-18. The parts of a finished roof.
The photo shows asphalt shingles being
installed on a new roof.
Rafter
Vent
Roof sheathing
Shingles
Soffit Fascia