12–1
19–5
17–8
16–7
14–10
23–7
21–1
19–3
17–2
no. 2
11–0
10–0
9–5
8–9
14–6
13–2
12–5
11–4
18–6 16–10
15–6
13–10
22–6
19–8
17–11
16–1
no. 3
9–8
8–5
7–8
6–10
12–4
10–8
9–9
8–8
15–0
13–0
11–10
10–7
17–5
15–1
13–9
12–4
Spruce- sel. struc.
11–0
10–0
9–5
8–9
14–6
13–2
12–5
11–6
18–6
16–10 15–10
14–8
22–6
20–6
19–3
17–11
pine-fir no. 1
10–9
9–9
9–2
8–6
14–2
12–10
12–1
11–3
18–0
16–5
15–5
14–1
21–11 19–11
18–3
16–3
(South) no. 2
10–5
9–6
8–11
8–3
13–9
12–6
11–9 10–10
17–6
15–11
14–9
13–3
21–4
18–9
17–2
15–4
no. 3
9–3
8–0
7–3
6–6
11–8
10–1
9–3
8–3
14–3
12–4
11–3
10–1
16–6
14–4
13–1
11–8
Western sel. struc.
10–9
9–9
9–2
8–6
14–2
12–10
12–1
11–3
18–0
16–5
15–5
14–3
21–11 19–11
18–6
16–6
woods
no. 1
10–5
9–6
8–11
8–0
13–9
12–4
11–4
10–1
17–5
15–1
13–10
12–4
20–3
17–6
16–0
14–4
no. 2
10–1
9–2
8–8
8–0
13–4
12–1
11–4
10–1
17–0
15–1
13–10
12–4
20–3
17–6
16–0
14–4
no. 3
8–5
7–3
6–8
5–11
10–8
9–3
8–5
7–6
13–0
11–3
10–3
9–2
15–1
13–1
11–11
10–8
* Design Criteria: Strength – 30 lb. per sq. ft. live load, plus 10 lb. per sq. ft. dead load. Deflection – Limited in span in inches divided by 360 for live load only.
This table is used courtesy of Western Wood Products Association (www.wwpa.org) and is excerpted from Western Lumber span tables of Floor and ceiling joists and roof rafters.
For more information about lumber grades, see pp. 58–59.
Latex acrylics are a good balance of perfor-
from product to product. Although some
mance, price, and workability.
manufacturers tout spectacular performance
Advantages: Latex acrylics are water
specs, check out online contractor chat groups
based, hence nontoxic, largely odor free, and
for real-life performance ratings.
easy to apply (you can shape caulk joints with
your finger). They clean up with soap and
water. They adhere well to a range of
materials, have good UV resistance, and can be
painted. Durable once cured, they are best
used in protected areas in temperate climates.
Disadvantages: Expect significant
shrinkage (up to 30%) and long curing times.
Although good as bedding caulk under door or
window casing, they’re iffy as exterior caulk or
shower and tub caulk. Properties vary widely
building materials
77
5 Roofs
A roof is a building’s most important layer of
defense against water, wind, and sun. Properly
constructed and maintained, a roof deflects rain
and snowmelt, and routes them away from other
house surfaces. Historically, roof materials have
included straw, clay tile, wood, and slate. Although
many of these materials are still used, most roofs
installed today are asphalt-based composites.
If roofs consisted simply of two sloping planes,
covering them would be easy. But today’s roofs
have protruding vent pipes, chimneys, skylights,
dormers, and the like—all potential water dams
and channels that need to be flashed to guide
water around them. Then, as runoff approaches
the lower reaches of the roof, it must be directed
away from the building by means of overhangs,
drip-edges, and—finally—gutters and downspouts.
This chapter assumes the foundation and
framing are stable. Because structural shifting or
settling can cause roofing materials to separate
and leak, you should fix structural problems
before repairing or replacing a roof.
Roof ventilation is another important part of
house health and comfort. Venting excessively
moist air can forestall condensation, mold, rot,
and, in colder climates, ice dams. Heat buildup
under the roof can also be mitigated by adequate
ventilation. The topic is so important that it is
discussed here and in chapters 7 and 14.
Roof Safety and Equipment
Among the building trades, roofing is considered
the most dangerous—not because it’s inherently
Although these wood shingles seem randomly placed, the installer is taking
hazardous but because it takes place high
great pains to offset the shingle joints between courses and maintain a
above the ground. The steeper the roof pitch
minimum exposure of 5 in. so the roof will be durable as well as distinctive.
is, the greater the risk. If heights make you
uneasy or if you�
�re not particularly agile, hire a
licensed contractor.
78
Reputation, License,
and insurance
Before hiring a roofing contractor, call your local
office of the Better Business Bureau to see if
complaints have been lodged and check with the
state licensing board to determine if the con-
tractor is properly licensed and bonded. Ask to
see current certificates of liability insurance
coverage and workers’ compensation. Otherwise,
even if a contractor misrepresents his creden-
tials, you could be liable for injuries the con-
tractor and his crew sustain on your property.
Commonsense safety
Stay off the roof unless you have a
compelling reason to be on it. Besides being
hazardous to you, walking on a roof can
damage roofing materials.
A gauge stop on the base of a pneumatic nailer can be used to set the correct shingle exposure.
If you must work on a roof, make sure
When the gauge stop is snug to the butt of a shingle, the next shingle above—placed against the
there’s a second person within earshot in case
nose of the tool—will be positioned correctly.
you fall or need help.
Don’t venture up when the roof is wet or
near freezing or extremely warm. When wet,
most roofing materials are slippery. Cold
asphalt shingles are brittle; warm asphalt can
stretch and tear. Always wear shoes with soft,
Warranty issues
nonslip soles.
If you observe product defects such as premature wear or curling, ask the roofing
Position ladder feet securely away from
company that installed the shingles to inspect them and advise you on warranty
the building about one-quarter of the ladder’s
issues. (Always keep records of installations.) If the roofer is reputable, he probably
extended length. Never lean sideways from a
ladder. If you can’t reach something while
has a longstanding relationship with the manufacturer and can exert more pressure to
keeping your hips within ladder sides, move
settle disputes than you could. If the original roofer isn’t cooperative, get a second
the ladder.
opinion from a competitor.
If you buy a good-quality 30-year shingle, however, product defects are rare.
When installing a roof, use scaffolding
with a safety rail. The most dangerous part of
Shingles will often shed water far longer than their stated warranty period. Moreover,
a roofing job—apart from tearing off shingles
roofs rarely fail in the field: They fail around the edges, around vents, at chimneys, at
and underlayment—is applying the first few
wall-to-roof flashing, and around skylights. Failures are usually caused by something
courses along the eaves.
that rusts or works loose, caulking that wears out, or nails that pull out because they
When walking on a roof, try to “walk on
were nailed through multiple layers of old shingles—or weren’t nailed to sheathing at
nails.” In other words, try to walk directly over
all. Leaks are rarely caused by shingle granules or substrate wearing out.
the rafters, where the sheathing is nailed. The
For this reason, I’m somewhat skeptical about so-called “lifetime shingles.” Who’s
roof will be less springy over rafters, and you’ll
going to be around to pay out or collect on defective shingles 50 years after they were
be less likely to break through rotten sheathing.
installed? Besides, most lifetime warranties cover only the cost of replacing the
Follow the roofing manufacturer’s instal-
materials, not labor costs, which are typically 75% to 80% of the job.
lation instructions, which often provide time-
and money-saving tips. Moreover, if roofing
has been correctly installed, manufacturers
are more likely to honor their warranties.
Roofs
79
equipment
roof, as shown in “Venting a Roof” on p. 90, can
prolong shingle life somewhat, but the key to a
Unless you are installing roofing systems that
long-lasting roof is the quality of the materials
need to be “torched” (heat-sealed with a propane
and attention to details, especially flashing
torch), you won’t need a lot of specialized equip-
around chimneys, skylights, and vent pipes.
ment or tools. Most of the items discussed here
In the long haul, shingles with a 30-year war-
are safety related.
ranty are a smarter buy than 20-year shingles
Footwear should be sneakers or other soft-soled
because they last significantly longer, even though
shoes that grip well on a roof. Old-time roofers
they cost only a little more. Typically, 75% of a
prefer boots with thick soles that are less likely to roofing job’s cost is labor.
be punctured by stray nails, but they are inflexi-
ble and don’t grip as well.
When it’s time to teaR off
scaffolding can make applying the first few
Short term, you can save money by installing a
courses along the eaves far safer. After the lower
new roof over an old one if local codes allow.
courses are installed, the scaffolding serves mainly However, new roofing applied over old (see p. 97)
as a staging area for materials and tools.
rarely lasts as long as roofing installed on a
stripped and properly prepared substrate.
roofing jacks enable you to work safely on roofs
You must tear off existing roofing under these
with a 6-in-12 pitch or steeper. (Several different
conditions:
roof pitches are shown in “Gutter Lip and Roof
Pitch” on p. 178.) Jacks also are indispensable
The roof already has two roofing layers. Two
platforms for storing materials. As you work up a is the limit for most local codes because it’s virtu-
roof, install additional pairs of jacks whenever
ally impossible to install a third layer that will lie
you must stretch to nail the next course. As
flat. Even if you could, three layers would be a
shown in the photo on p. 78, many roofers leave
nightmare to flash and nail correctly. Underlying
jacks installed until the job is almost completed.
shingle layers are a springy substrate to nail
through, and old wood shingles often split and
Full-body harnesses, also known as personal
migrate. Besides, if the bottom layer is wood
fall-arrest systems (PFAS), may be required by
P R O T I P
shingles over skip-sheathing (1-in. boards with
local building authorities if a roof exceeds a cer-
spaces between), only half of the new roofing
tain pitch or if the eaves are more than a speci-
as you prepare to install roof-
nails would be likely to hit sheathing. Additional
fied height above the ground. If harnesses are
ing components, imagine rain-
layers would be poorly attached and therefore
required, have someone at the rental comp
any
water running down the roof. to
wouldn’t last. Also, multiple layers of shingles put
demonstrate correct use.
prevent water running under-
a tremendous strain on framing and sheathing.
neath underlayment, flashing, or
Knee pads, sturdy ones with integral plastic
shingles, roofing materials
cups, will spare you a lot of pain. In addition, get
upslope must always overlay
a foam kneeling pad such as those gardeners use;
those below.
it will allow you to sit or kneel while shingling
and will protect shingles from abrasion.
a pneumatic nailer, which you can rent, speeds
Roof Longevity
the job along. Have the rental company recom-
mend nails and explain the nailer’s correct use.
MATerIAL
LOngevITy (years)
shingling hatchets in the hands of a pro can fas-
slate and tile*
80
ten shingles almost as fast as a pneumatic nailer.
Miscellaneous tools
Wood shingles or shakes
include a utility knife with
30–40
hooked blades, a straightedge or framing square,
metal
40–50
a hammer, a chalkline, a tape measure, caulk
20–50 (depends
guns, work gloves, safety glasses, and hearing
asphalt shingles
on warranty
protection.
three-ply built-up roof
15–20
Preparing to Install
four-ply built-up roof
20–25
a New Roof
*Underlayment quality also determines how many leak-free
Daily temperatures on a roof or in an unventilated
years you can expect. With 15-lb. building paper underneath,
attic can swing from 50°F to 150°F, thereby caus-
a tile roof might start leaking in 15 years; modified bitumin
ing tremendous expansion and contraction of
under tile could help create an 80-year roof.
roof materials. Improving ventilation under the
80
Chapter 5
sheathing and rafters show extensive water
broom) and roll the lawn to locate roofing nails—
damage. When you can’t determine exactly
before your lawn mower does it for you.
what’s been causing leaks, it’s time to strip. The
And don’t forget the inside of the attic. Spread
previous roofers may have installed flashing
plastic tarps over attic floors, especially if there’s
incorrectly or not at all. Or roofers may have left
insulation between the joists. During tearoff, an
tired old flashing in place. Whatever the cause, if
immense amount of debris and fine dust falls
the remedy is stripping back extensive sections of into an attic. Unless you catch it in plastic and
Renovation 4th Edition Page 19