Renovation 4th Edition
Page 24
If the old roof was once covered with wood
out or missing flashing. Or, in some cases, it’s
shingles, they were likely nailed to skip-sheathing,
necessary to disturb shingles to install a roof vent which consists of widely spaced 1-in. boards
or a vent pipe.
that allow air to circulate under the shingles and
When removing a shingle or a course of shin-
dry them. These days, most roofers cover skip-
gles, disturb surrounding shingles as little as pos-
sheathing with plywood because it stiffens the
sible. First, break the adhesive seal between
roof and is safer to walk on. But nailing shingles
courses by sliding a mason’s trowel or a shingle
directly to plywood or building paper impedes air
98
Chapter 5
Wood shingle Basics
If the old wood shingle roof was attached to
zzzzzz Wood shingle details
no matter how wide the wood shingle, use only
skip-sheathing, cover it with plywood for safety
two nails—placed 3⁄
and stability. A layer of synthetic mesh allows
Solid plywood
4 in. in from the edge and
the underside of the wood shingles to dry out.
sheathing
11⁄2 in. above the exposure line. To allow for
expansion, leave a 1⁄4-in. gap between shingles,
Old skip-sheathing
unless they are wet, in which case you can place
Two nails per shingle,
them snugly against each other. Offset joints
in 3/4 in. from edges
Felt paper
between successive courses at least 11⁄2 in.
Shingle joints that line up must be separated by
Mesh allows
shingles to breathe.
two courses—in other words, shingle joints can
line up every fourth course but not sooner.
Finally, nail heads should touch but not crush
shingle surfaces; any deeper and they may split
the wood.
1/4-in.
circulation and may lead to cupping (shingles’
gap
undersides will dry much more slowly than the
tops), rotting, and shortened shingle life.
Double first course
One answer to this dilemma is a layer of
of shingles along
Fascia board
1⁄4-in.-thick synthetic mesh between the building
eaves.
paper and the shingles. Cedar Breather is one
Offset shingle joints
brand, which comes in 39-in.-wide rolls. Roll the
11/2 in. minimum.
Shingles overhang
mesh out over 30-lb. building paper, tack or staple
1 in. at eaves and rake.
it down, and you’re ready to shingle. The mesh
retains enough loft to allow air to circulate freely
under the shingles so they can dry fully. To attach
shingles over the mesh, you’ll need longer nails:
Alternate direction
zzzzzz Ventilating a Wood shingle Ridge of shingle-cap
6d shingle nails should do, but check the product’s
overlaps.
literature to be sure.
Flash a wood shingle roof as you would an
Ridge vent
asphalt roof, including WSU along the eaves,
rakes, and valleys and metal drip-edge along the
Cut back sheathing
eaves and rakes.
from ridgeboard by
1 in. minimum.
estimating mateRiaLs
Urethane
caulk
Use only No. 1 (blue-label) shingles on roofs
because they’re free of sapwood and knots.
Lesser grades are fine for siding but may leak on
a roof. Shingles come 16 in., 18 in., and 24 in.
long, with recommended exposures of 5 in.,
51⁄2 in., and 71⁄2 in., respectively, on roofs with a
4-in-12 slope or steeper. Ultimately, slope deter-
mines exposure and thus the number of bundles
per square (100 sq. ft.).
In general, four bundles will cover a square.
To calculate the number of squares you’ll need,
Felt paper
Cedar Breather
calculate the square footage of the roof and
(synthetic mesh)
divide by 100. Because shingles are doubled
Solid sheathing
along eaves and rakes, add an extra bundle for
each 60 lin. ft. of eaves or rake. For valleys, add
Use a pneumatic nailer to attach
an extra bundle for each 25 lin. ft. For ridges and
preassembled ridge caps over the ridge vents
roof hips, buy preassembled ridge caps, sold in
because hand nailing the caps could split them.
Roofs
99
GoT moss?
Moss-covered shingles and shakes are common
in moist, shaded areas. Hand-scrape or use a
wire brush to take the moss off. keep it off by
stapling 10-gauge or 12-gauge copper wire to
a course of shingle butts all the way across the
roof. run one wire along the ridge and another
halfway down. during rains, a dilute copper
solution will wash down the shingles, discourag-
ing moss. It’s a nice alternative to toxic
chemical treatments.
You could snap chalklines to indicate expo-
sures for successive courses, but chalk can be
unsightly and slow to fade on wood shingles.
After installing drip-edge flashing,
Instead, get a straight board as wide as the shin-
double the first course of wood
gle exposure (5 in., for example), place its bottom
shingles along the eaves. Along eaves bundles that cover 16 lin. ft. One Canadian sup-
edge flush to the bottom of the last shingle
and rakes, the drip-edge overhangs
plier, WoodRoof (www.woodroof.com), has an
course, and position the next course of shingles
sheathing or trim boards by 1⁄2 in. to
especially informative website about hip and
by simply placing them atop the board. Move
3⁄4 in., and shingles extend at least
ridge caps, precut “fancy butt” shingles, specialty loose shingles around until all their joints are
1 in. beyond the drip-edge.
tools, and more.
correctly offset to the courses below, then nail
You’ll need 2 lb. of 4d or 5d galvanized shingle them down. A single shingle nail at either end of
nails per square of shingles. For shingle caps
the “nailing board” will tack it in place.
along ridges and hips, use 6d shingle nails to
When you must stretch to install courses
accommodate the greater thickness of materials.
above, install roof jacks as described on p. 95.
Have your supplier deliver the materials in a lift-
Because wood shingles have random widths
bed truck so that you can unload the shingles
(unlike the fixed lengths of asphalt shingles),
directly onto the roof.
several people can work on a course at the same
time. As you get within 6 ft. of the top, measure
instaLLing Wood shingLes
up to the ridge. If the ridge is not parallel to the
P R O T I P
eaves, there may be a discrepancy of s
everal inches
Note the offset requirements in “Wood Shingle
between measurements at one end of the roof and
save exceptionally wide
Basics” (p. 99), which are essential for a long-
the other. If so, start adjusting exposures so that
wood shingles to use along a val-
lasting roof.
the top course of shingles will be more or less
ley, so you can nail as far as pos-
Double the first courses of shingles along the
sible from the center of a valley.
parallel to the ridge. If there’s a discrepancy of
eaves, extending them beyond the drip-edge by
no matter how wide that shingle
2 in., for example, you should reduce exposures
1 in. Double shingles along rakes, overhanging
is, use only two nails to secure it.
on the narrow end of the roof by 1⁄4 in. per course.
rake trim by 1 in. In addition, install metal drip-
if you think a shingle may split,
edge along eaves and rakes. When nailing the
open valleys. Refer to previous sections in this
flex it gently to be sure it’s
bottom course of doubled shingles along the
chapter on underlayment and valley flashing
sound.
eaves, nail them about 1 in. up from the butt
before you start. For most wood-shingle roofs, an
edges; if possible, sink the nails into the edge of
open valley is the way to go. The exposed metal
the fascia board. Those two nails will be covered
flashing clears water effectively and it’s not likely
by the top course of doubled shingles. Nail that
to clog with debris. In addition, shingles running
course with two nails placed 11⁄2 in. above the
alongside an open valley require less fitting and
exposure line.
cutting than those in closed valleys.
You can shingle out from a valley or into a val-
ley from roof planes on either side. In either case,
start by snapping parallel chalklines along both
sides of the metal valley flashing; each line should
be at least 3 in. from the center fold of the flash-
ing. As each course approaches the valley, don’t
100 Chapter 5
nail the last four or five shingles immediately;
shingLe RepaiRs
just arrange them so that wide shingles end in
To remove wood shingles, use scrap blocks to ele-
the valley. Where shingles cross a chalkline, use a vate the butt ends of the course above. Work the
utility knife to notch the shingle at those points.
blade of a chisel into the butt end of the defective
Keep nails as far as possible from the valley
shingle, and with twists of your wrist, split the
center: 5 in. away is minimum. A bead of ure-
shingle into slivers. Before fitting in a new shin-
thane caulk under the leading shingles should
gle, remove the nails that held the old one. Slide
keep the edges from lifting.
a hacksaw blade or, better, a shingle ripper (also
closed valleys. Run shingles into the valley until known as a slate hook) up under the course
they meet oncoming shingles from the other side. above and cut through the nail shanks as far
At that juncture, rough-cut each shingle about 1⁄4 in. down as possible. If you use a hacksaw blade,
proud to establish the correct angle. Then use a
wear a heavy glove to protect your hand.
block plane to back-bevel the leading edge. By
Wood shingles should have a 1⁄4-in. gap on
cutting and planing, you create a compound
both sides, so size the replacement shingle 1⁄2 in.
angle so that the shingles fit tightly; this can be
narrower than the width of the opening. Tap in
done only on the roof, shingle by shingle—a slow the replacement with a wood block. If the
job. For best weathering, alternate miters right
replacement shingle won’t slide in all the way,
and left from course to course. Build up several
pull it out and whittle down its tapered end,
courses in the valley, and shingle out to the rest
using a utility knife. It’s best to have nail heads
of the field.
covered by the course above, but if that’s not pos-
ridge treatments. Be sure to read the com-
sible, place a dab of urethane caulk beneath each
ments on venting a ridge on pp. 90–91. In brief,
nail head before hammering it down. Use two 4d
cut back sheathing at least 1 in. on either side of
galvanized shingle nails per shingle, each set in
3
the ridge board. Then run underlayment and
⁄4 in. from the edge.
shingles to the edge of the sheathing before nail-
ing a ridge vent over the opening.
A Medley of Roofing Types
The ridge vent can be finished in one of
Although this section covers modest repairs a
two ways:
novice can make, most of the roofs discussed
Shingle caps. Use a pneumatic nailer to
here should be installed by a specialist. You’ll
attach preassembled shingle caps over the
also find suggestions for determining the quality
vent. Because the mesh underlayment and the
of an installation as well as a few tips.
ridge vent are compressible, they would move
if you tried to hand-nail them. Shoot 2-in. to
fLat Roofs
21⁄2-in. galvanized shingle nails through the
shingle caps; nails should penetrate the roof
Actually, no roof should be completely flat, or it
sheathing at least 1⁄2 in.
won’t shed water. But “flat roof” is a convenient
term for a class of multimembrane systems. At
Ridge boards. These butt to each other;
one time, built-up roofs (BURs) once represented
for a weathertight fit, they should be mitered.
half of all flat roof coverings. BURs consisted
To establish the miter angle, lap two pieces of
of alternative layers of heavy building paper and
scrap at the peak and, using an adjustable
hot tar. Today, modified bitumin (MB) is king,
bevel, transfer this angle to your tablesaw.
with cap membranes torched on to fuse them to
Test-cut several pieces of scrap until the fit is
fiberglass-reinforced interplies or base coats.
tight, then rip down the ridge boards on the
MB systems are durable and adhere well to dis-
tablesaw. Because ridge boards should be as
similar materials and difficult joints, but an
long as possible, get help nailing them down. If
inexpert torch user can damage the membranes
it takes several boards to achieve the length of
and set a house on fire. For that reason, future
the ridge, bevel end joints 60° and caulk each
roofs are likely to employ hot-air welding, cold-
with urethane caulk. Using 8d galvanized ring-
press adhesives, and roll membranes with self-
shank roofing nails, nail the ridge boards to
sticking edges.
the rafters, using two nails per rafter. Then go
back a
nd draw the beveled joint together by
causes of flat-roof failure. Whatever the
nailing it with 6d galvanized box nails spaced
materials, flat roofs are vulnerable because water
every 12 in. As you work, push down on the
pools on them, people walk on them, and the
ridge boards to force them together. To avoid
sun degrades them unless they’re properly
splitting boards, predrill them or use a
maintained. Here are the primary causes of
pneumatic nailer to shoot nails through the
membrane damage:
roofing layers into the rafters.
Roofs
101
LAyING A FLAT ROOF
Once the granular membrane is down, its overlapping
edges are often lifted and torched again to ensure sound
adhesion and a waterproof seam.
The intersection of flat and sloping
roof sections is worth extra attention.
Run MB membranes at least 10 in.
In the final phase of a modified bitumen roof, an installer
Roofers refer to the molten material being forced out by
(vertical height) up the sloping
torch-welds a granular surface membrane to an interply
the pressure of the trowel as wet seams—the mark of a
section. Then overlap those mem-
sheet or directly to a base sheet. The granular surface
successful installation.
branes with the underlayment
is somewhat more expensive at installation, but it is
materials and the composition
cost-effective in the long run because it doesn’t need
roofing material so water can run
periodic recoating.
down unimpeded.
Water trapped between layers because
Trowel on a 1⁄4-in.-thick layer of an
the roofing was installed too soon after rain or
elastomeric mastic, such as Henry 208 Wet
when the deck was moist with dew. Trapped
Patch®, carefully working it into both sides of
water expands, resulting in a blister in the
the split. Extend the mastic at least 2 in.
membrane. In time, the blister is likely to split.
beyond the split in all directions.
Inadequate flashing around pipes,
Cut a piece of “yellow jacket” (yellow
skylights, and adjoining walls.
fiberglass roofer’s webbing) slightly longer
than the split and press it into the mastic; this
Drying out and cracking from UV rays—
reinforces the patch.
usually after the reflective gravel covering has
been disturbed.