| WALL OPENINGS
In addition to doors and
windows (Chapter 8), other wall
openings are needed.
STOVEPIPES
Stovepipes may extend outside
a building through a side wall
to eliminate the need for
flashing and waterproofing
around the pipe (Figures 6-47
and 6-48). The opening should
be cut in an area selected to
avoid cutting studs, braces,
plates, or other structural
members. Sheathing must be
cut back in a radius 6 inches
greater than that of the pipe.
Safety thimbles or other
insulation must be used on the
inside and outside of the
sheathing. Sheet metal insulation may be constructed and used as a single
insulator on the
outside.
Make the opening for the stovepipe as follows:
Step 1. Cut a hole through the sheet metal where the stovepipe will
penetrate.
Step 2. Mark a circle on the metal 1/2 inch larger in diameter than
the pipe. Then make another circle within this circle, with a diameter
2 inches less than the diameter of the first.
Step 3. With a straightedge, draw lines through the center of the circle
from the circumference. These marks should be from 1/2 to 3/4 inch apart
along the outer circumference.
Step 4. Cut out the center circle, then cut to the outside of the circle
along the lines drawn.
Step 5. After the lines have been cut, bend the metal strips outward
at a 45° angle.
Step 6. Force the pipe through the hole to the desired position.
NOTE: Very little water will leak around
this joint.
VENTILATORS
Ventilation is necessary to prevent
condensation in buildings. Condensation may
occur in the walls, in the crawl space under
the structure, in the basement, on windows,
and in many other places. Condensation is
most likely to occur during the first six to
eight months after a building is built and in
extreme cold weather when interior humidity is high. Proper ventilation
under the roof allows moisture-laden air to escape during the winter heating
season and allows the hot, dry air of the summer season to escape. The
upper areas of a structure are usually ventilated by louvers or ventilators.
(Types of ventilators are shown in Figure 6-49.)
Upper Structure
One of the most common methods of ventilating is to use wood or metal
louver frames. There are many types, sizes, and shapes of louvers.
Determine the size and number of ventilators by the size of the area
to be ventilated. One square foot of vent should be placed for each 150
square feet of floor space without soffit vents and for each 300 square
feet of floor space with soffit vents. The minimum net open area should
be 1/4 square inch per square foot of ceiling area.
Louver frames are usually 5 inches wide. The back edge of the frame
should be rabbeted out for a screen, a door, or both. Louvers have ¾-inch
slats, which are spaced about 1 3/4 inches apart. The slats should have
sufficient slant or slope to prevent rain from driving in. For the best
results, upper-structure louvers should be placed as near to the top of
the gable as possible.
Crawl Spaces
Crawl spaces under foundations (of structures without basements) should
be well ventilated. Air circulation under the flooring prevents excessive
condensation which causes warping, swelling, twisting, and rotting of
the lumber. The crawl space ventilators are usually called foundation
louvers. They are set into the foundation as it is built. A good foundation
vent should be equipped with a copper or bronze screen and adjustable
shutters for opening and closing the louver. Louver sizes should be figured
on the same basis as upper-structure louvers 1/4 square inch for each
square foot of under-floor space.
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