Renovation 4th Edition
Page 22
Passive ventilation: As air heats under
rafters to block the rising air. slotted intake vents are, essentially, a
the roof, it rises and exits through the ridge
one-sided ridge vent. they require several courses of shingles to be
vent, drawing cooler air up through soffit
vents or vented drip-edges. Venting also
removed, a 1-in. slot cut through the sheathing, and the intake vent to
Soffit vent
carries off excess moisture.
be integrated into the shingle field so that it overlaps the course
below and is overlapped by the course above.
adding intake vents, however, may not be a viable solution if raf-
ters are not deep enough to accommodate both insulation (R-30
requires 8 in. of insulation) and 2 in. of clear space above the insula-
tion to allow airflow. solid wood blocking between rafters also will
stop airflow, creating hot spots of stagnant air between rafter bays. at
some point, it may be more cost-effective to opt for an unvented
roof—closing all vents to the exterior, insulating the underside of the
roof, and turning the attic into conditioned space. doing so may
increase the amount of living space you have, provided the attic is
framed to support live loads and is accessible. unvented roofs and con-
ditioned attics are discussed further in chapter 14 beginning on p. 398.
mVR = minimum Venting Requirements
Chapter 14 offers more information on ventilation. in brief, you need a
minimum of 1 sq. ft. of ventilation per 300 sq. ft. of attic space. half
the vent area will be intake vents, and half ridge or gable-end exit
vents. for example, if attic floor space totals 2,500 sq. ft., total vent
surfaces should be 2,500 ÷ 300, or 8.33 sq. ft. Ridge vents would
therefore be half that, or 4.16 sq. ft. that area corresponds roughly to
33 lin. ft. of ridge vents, based on net free vent area (nfVa) charts.
Intake vents take many forms, including slotted
vents that resemble half of a ridge vent. Intake
vents are typically installed a few feet up from,
and parallel to, the eaves.
[PHOTO CREDIT: Mike Guertin]
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Chapter 5
Where complex roof framing or closed
eaves rule out using ridge vents or slotted
intake vents, eyebrow ventilators and
rooftop turbines can help reduce heat in
the attic.
Have a boom truck deliver roofing
supplies directly to the roof. Stack
pattern, with no shingle cutouts to line up. When materials along the ridge so the rest
installed, they look distantly like wood shakes.
of the roof will be clear to work on.
mateRiaLs: Rough numBeRs
Shingle dimensions vary by maker. Three-tab
shingles are typically 12 in. by 36 in. Laminated,
architectural shingle dimensions are often metric,
roughly 13 in. by 40 in. Most shingles are
installed with a 5-in. exposure, although shingles
with metric dimensions may specify a 55⁄8-in.
P R O T I P
exposure. Always follow the manufacturer’s expo-
sure recommendations, no matter what type of
When reroofing an old house,
shingle it is.
make sure rafters can support the
calculating shingles needed. Begin by measur-
weight of new shingles. some
ing the roof accurately, making a sketch to scale
thick “luxury shingles” weigh
on graph paper as you go. Note valleys, ridges,
480 lb. per square versus 250 lb.
chimneys, skylights, plumbing vents, and other
per square for 30-year architec-
tural shingles or 200 lb. for stan-
elements that require flashing, waterproof mem-
dard three-tab singles.
branes, or special attention. From that sketch, a
building supplier can develop a final materials
list for shingles, nails, underlayment, flashing,
vents, and so on.
Asphalt shingles come three to five bundles to
the square (100 sq. ft.), depending on shingle
dimensions. To calculate the number of squares
Ridge vents allow hot air—and excess
you’ll need to shingle the field, add up the square
moisture—to exit the building. Here, a
footage of roof surface and divide by 100. In
perforated plastic ridge vent gets capped
addition, you’ll need materials to reinforce shin-
with shingles.
gles along eaves and rake edges—either by
installing a double layer of shingles along the
roof perimeter or by applying a heavy starter strip
before shingling.
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91
If you’re installing laminated shingles, use
nails per shingle, you’ll need about 31⁄3 coils
three-tab shingles as an underlayer along the eaves (400 nails) to attach a square of shingles.
and rakes. For this purpose, three-tab shingles
Use corrosion-resistant roofing nails at least
are far cheaper than laminated shingles and will
11⁄4 in. long for new roofs; use 11⁄2-in. nails if
lie flatter. If you’re installing woven valleys, you’ll you’re roofing over a previous layer. Ideally, nails
interweave roughly one bundle of shingles per
should sink three-quarters into sheathing or stop
16 lin. ft. of valley. Finally, add two extra bundles
just short of penetrating all the way through for
1
for waste, ridge and hip caps, and future repairs.
⁄2-in.- to 5⁄8-in.-thick sheathing. If the roof has an
Shingle colors often vary from one production exposed roof overhang (you can see the under-
lot to another. To avoid having a new roof with a
side of the sheathing), use 3⁄4-in. nails (along the
patched-together look, specify that all bundles
overhang) for a new roof; 1-in. nails for roofovers.
come from the same lot when you order. When
When ordering, don’t forget tabbed roofing
your order arrives, check the lot numbers on the
nails for underlayment and metal-compatible
bundles and open a few bundles from different
nails for attaching flashing or valley clips.
lots. If lot numbers don’t match and the color
variation is noticeable, call the supplier. If the
shingLe Layout
color varies only slightly, you might mix lots
We’ll assume that the roof has been stripped of
every other shingle during installation. Finally,
old shingles, that failed sheathing has been
have shingles delivered directly to the roof. Many replaced, and that the roof is safe to walk on.
suppliers will place bundles on the roof by means reconnoiter the roof. Use a tape measure to see
of truck booms or conveyor belts.
whether the roof is square, the ridge is parallel to
roofing nail quantities vary according to
eaves, the rake edges are parallel, and whether—
method: hand nailing, power nailing, or some
overall—the width of the roof requires shifting
combination of the two. Typically, use four nails
shingle courses left or right. To determine square,
&n
bsp; per shingle, or about 2 lb. of nails per square if
measure diagonally from both ends of the ridge
you’re hand nailing. However, high-wind areas
down to the opposite eave corner; if the readings
require six nails per shingle, or 3 lb. per square.
are roughly equal, chances are the roof is square.
Roofing nails come in 5-lb. and 50-lb. quantities.
If the ridge is parallel to eaves within 1⁄2 in., run
Boxes of pneumatic nails typically contain
shingle courses right up to the ridge. But if ridge-
120 nails per coil and 60 coils per box. At four
to-eaves readings differ by 3⁄4 in. or more, you’ll
shingling terms
these definitions will help you make sense of roofing terms.
course: a horizontal row of shingles.
zzzzzz three-tab shingles
Butt edge: the bottom edge of a shingle.
Tab
Offset
exposure: typically, the bottom 5 in. of the shingle, left
Self-seal strip
exposed to weather. shingles with metric dimensions are usually
exposed 55⁄8 in.
cutouts: slots cut into the exposed part of a three-tab shingle
to add visual interest and allow heat expansion.
Offset: the distance that shingle slots or ends are staggered
from course to course.
Self-seal strip: the adhesive on the shingle face, which,
when heated by the sun, fuses to shingles above and prevents uplift.
Fastener line: on shingles with a 5-in. exposure, a line roughly
Exposure
55⁄8 in. up from the butt edge. nails along this line will be covered by
the shingles above. (if shingles don’t have such lines marked, nail just
below the self-seal strip.)
Butt edge
Cutouts
control lines: Chalklines snapped onto underlayment to help
align courses and cutout lines.
Fastener line
(not found on all shingles)
underlayment: a water-resistant sheet material—usually
building paper—that covers the roof sheathing.
92
Chapter 5
need to compensate by adjusting shingle expo-
sures as you approach the ridge.
The last two measurements, for parallel rakes
and roof width, are of most concern if you’re
installing three-tab shingles. Because three-tab
shingle patterns align vertically, avoid cutting
shingle tabs less than 2 in. wide along either rake
edge—tabs that short look terrible. It’s far better
to shift the shingle layout (and thus the vertical
control lines) slightly right or left so the shingle
piece is larger. For additional strategies for
installing three-tab shingles, see Mike Guertin’s
fine book, Roofing with Asphalt Shingles (The
Taunton Press, 2002).
establishing control lines. After installing drip-
edge along the eaves, many pros measure only
once, to establish a horizontal control line paral-
lel to the eaves, to which they nail the shingle
starter course. After the starter course is down,
they use only the exposure gauge of their pneu-
matic nailer or shingle hatchet to position suc-
cessive courses.
After installing drip-edge along the eaves, double the first course of shingles or, as shown, install a
starter strip. The lower edge of the starter strip overhangs the drip-edge by 1⁄
To make sure courses stay evenly spaced and
4 in. to 3⁄4 in.—or even
1 in. if bowing eaves or rake boards require it.
straight, however, snap horizontal chalklines at
regular intervals onto the underlayment (build-
ing paper). Snapping chalklines every second or
third course won’t take much time and will
ensure professional-looking results.
If you’re installing three-tab shingles, it’s also
wise to snap a pair of parallel, vertical control
lines 6 in. apart to line up the slots of alternating
shingle courses, as shown in “Laying Out Three-
Tab Shingles” on p. 95. With a 6-in. offset, the
slots of every other course line up, creating a
strong visual pattern. If slots don’t align, the
installation will look sloppy. Laminated shingles
have no slots to align, so you won’t need vertical
control lines.
instaLLing shingLes
After attaching drip-edge to the eaves and rolling
out underlayment over the drip-edge, install the
starter course along the eaves. You’ll cover the
starter course with the first course of shingles.
Instead of doubling shingles along the roof rakes,
Running starter courses along the rakes isn’t
install a starter strip. It’s stiff enough to resist wind
imperative, but it’s smart because starters stiffen
uplift. And, seen from below, it presents a much
P R O T I P
cleaner, straighter line than individual shingles.
the overhanging shingle edges and create a clean-
er sightline from below.
many roofers prefer hand nail-
The starter course. First, determine how much
ing the first half-dozen shingle
the starter course will overhang the drip-edge:
courses rather than pneumatic
1⁄
nailing. that’s because the hose
4 in. to 3⁄4 in. overhang is typical, but some roof-
ers allow as much as 1 in. if eave or rake boards
of a pneumatic nailer makes foot-
are bowed.
ing more treacherous along the
eaves, where there’s little time to
Along the eave, extend your tape measure past
catch yourself before rolling over
the drip-edge the amount of the overhang. If that
the edge.
overhang is 1 in., make crayon marks on the
underlayment at 7 in. and at 12 in. Do this at
Roofs
93
both ends of the roof, and snap chalklines
unbroken line. Still, trimming three-tab shingles
P R O T I P
through both sets of marks. The 7-in. line indi-
is cheaper, so here’s a quick look at that method.
cates the top of the starter course; the 12-in. line
Traditionally, the starter course was just a full
score shingles on the back-
indicates the top of the first course of shingles.
shingle turned upside down so its tabs faced up,
side, using a utility knife. if you
Starter courses can be three-tab shingles with
but that placed the shingle’s self-seal strip too
try to cut through the granules
the bottom 5 in. cut off or a starter strip that
high to do much good. It’s far better to measure
on the front, the blade will go
awry and soon dull. When you
comes on rolls in various widths. Starter strips
down 7 in. from the top of the shingle, trim off
score along a straightedge and
have the advantage of stiffening shingles above
the bottom 5 in., and snap off the shingle tabs.
snap along the cut, you’ll get a
and, viewed from below, providing a cl
ean,
Align the top edge of the starter shingles to
straight, clean edge.
the 7-in. control line and nail them down, four
nails per shingle. If you’re installing a starter
strip, align its top edge to the 7-in. control line.
Next, install starter courses over rake drip-edges,
using the same overhang you used for eaves.
Rake starter strips overlap eave starter courses
using pneumatic nailers
when they meet at lower corners. Along both ends
of the roof, measure up from the 12-in. control
Because pneumatic nailers can easily blow nails through shingles, some codes spec-
line and snap horizontal chalklines for the shin-
ify hand nailing. and it’s safer to hand-nail the first five or six courses along the eaves,
gle courses to come. As noted earlier, a horizontal
where stepping on a pneumatic hose could roll you right off the roof. Wear safety glasses
chalkline every two or three shingle courses is
when using nailers.
plenty. Once that’s done, you’re ready to install
those concerns aside, pneumatic nailers are great tools if used correctly. here’s how:
the first course of shingles.
don’t bounce-fire a nailer until you’re skilled with it. (to bounce-fire, you hold
One final note: Building-paper underlayment
the trigger down and press the nailer’s nose to the roof to fire the nail.) shingles must
tears pretty easily if it gets too much traffic, so
be nailed within a small zone—below the sealer strip but above the cutouts, if any—
only roll out one strip of building paper at a
and it’s hard to hit that zone if the nailer is bouncing around. instead, position the
time. Install shingle courses until you are close
nailer nose where you want it, then pull the trigger.
to the upper edge of the felt paper, then roll out
trigger-fire the first nail of every shingle. do this to keep shingles from slipping,
the next strip so that its lower edge overlaps the
even if you’re skilled with pneumatic nailers. once the first nail is in, you can bounce-
one below.
fire the remaining ones.
shingling the field. Install the first course of
hold the nailer perpendicular to the roof so nails go in straight, and keep an eye
shingles over the starter course. If you’re right-
on nail depth as the day wears on. nail heads should be flush to the shingle; if they’re
handed, start at the left side of the roof and work
underdriven or overdriven, adjust the nailer pressure.