Figure 3-24.-Laying out a shingle roof.
is 4:12 or greater. When special application methods are
used, organic- or inorganic-base-saturated or coated-
strip shingles can be applied to decks having a slope of
4:12, but not less than 2:12. Figure 3-23 shows the
application of shingles over a double layer of
underpayment. Double underpayment is recommended
under square-tab strip shingles for slopes less than 4:12.
When roofing materials are delivered to the building
site, they should be handled with care and protected
from damage. Try to avoid handling asphalt shingles in
extreme heat or cold. They are available in
one-third-square bundles, 27 strip shingles per bundle.
Bundles should be stored flat so the strips will not curl
after the bundles are open. To get the best performance
from any roofing material, always study the
manufacturers directions and install as directed.
On small roofs (up to 30 feet long), strip shingles
can be laid starting at either end. When the roof surface
is over 30 feet long, it is usually best to start at the center
and work both ways. Start from a chalk line
perpendicular to the eaves and ridge.
Asphalt shingles will vary slightly in length (plus or
minus 1/4 inch in a 36-inch strip). There may also be
some variations in width. Thus, chalk lines are required
to achieve the proper horizontal and vertical placement
of the shingles (fig. 3-24).
The first chalk line from the cave should allow for
the starter strip and/or the first course of shingles to
overhang the drip edge 1/4 to 3/8 inch.
When laying shingles from the center of the roof
toward the ends, snap a number of chalk lines between
the eaves and ridge. These lines will serve as reference
marks for starting each course. Space them according to
the shingle type and laying pattern.
Chalk lines, parallel to the eaves and ridge, will help
maintain straight horizontal lines along the butt edge of
the shingle. Usually, only about every fifth course needs
to be checked if the shingles are skillfully applied.
Inexperienced workers may need to set up chalk lines
for every second course.
The purpose of a starter strip is to back up the first
course of shingles and fill in the space between the tabs.
Use a strip of mineral-surfaced roofing 9 inches or wider
of a weight and color to match the shingles. Apply the
strip so it overhangs the drip edge 1/4 to 3/8 inch above
the edge. Space the nails so they will not be exposed at
the cutouts between the tabs of the first course of
shingles. Sometimes an inverted (tabs to ridge) row of
shingles is used instead of the starter strip. When you