| (Reprinted
From This Old House Magazine)
By Brad Lemley
As Walter Cromwell cranes his neck to survey the scene, a slight
smile breaks across his face: On the steep roof pitches of his house-to-be,
a half-dozen carpenters are arrayed here and there, some scurrying
gingerly along the ridges and staging, others hunkered down with
chuffing pneumatic nailers. The unmistakable aroma of cedar sweetens
the air, and Cromwell likes what he sees: steady progress toward
what will be a thoroughly handsome roof. Among the hundreds of decisions
he’s made during the construction of T.O.H.’s Wilton,
Connecticut, Dream House, the one that led to this tableau was easy:
choosing red cedar roofing and siding shingles. "After all,"
he says with a shrug, "it’s a Shingle Style house."
True enough, cedar shingles have been the sine qua non of this playful
architectural genre since it first appeared in the 1880’s.
Choosing a different material would have been tantamount to slapping
a beanie on a beefeater. Cedar’s appeal stems in part from
its close connection to America’s architectural traditions.
"Up until the turn of the century, when asphalt and metal became
widely available, wood shingles were the norm, at least in the northern
states," says architectural conservator Andrea Gilmore. The
earliest wood shingles were made of oak, pine and redwood as well
as cedar but, by the turn of the century, cedar had captured most
of the wood-roof market. Today, cedar still dominates, not only
because of its formidable rot-resistance but also due to its surpassing
beauty.
As the completed pitches at the Dream House so amply demonstrate,
cedar’s good looks can’t be replicated by any other material.
Warm-toned and subtly textured, each shingle is ever so slightly
different from the ones next to it, and in a year or two they’ll
all weather from reddish browns to silver grays. On any house that
makes a show of its roof design – be it traditional or contemporary
– cedar shingles heighten the drama.
Choosing cedar’s beauty, however, also means paying top dollar
for a roof. The material alone costs three times as much as the
best quality asphalt shingles, and the skill and time required to
install cedar – one 5- to 12-inch-wide shingle at a time –
increases the cost gap even more. A finished cedar roof can cost
up to $34 a square foot, compared to $10 for asphalt.
"It would take six or seven guys two to three weeks to finish
this, if we did it full-time," says carpenter Ray Chizmar,
straddling a ridge and waving a calloused hand over the 7,000-square-foot
Dream House roof. "With asphalt, we’d do it in four days.
Asphalt is mindless. You just align the strips and go. Cedar takes
some fiddling." And well it should because only with careful
installation – and regular maintenance later on – will
the investment in cedar pay off with a roof that’s long-lived
and trouble-free.
At the moment, Chizmar is fiddling in earnest, flipping through
a stack of shingles to find one wide enough to go above a rank of
narrower ones." It’s best if you stagger the joints between
three rows," he says. In other words, a straight-edge aligned
with a joint should miss joints on the two rows, called courses,
by at least an inch. Finding a 10-inch-wide shingle, Chizmar tests,
then triumphantly slaps it into place, promptly pinning it with
nails as if to prevent its escape. Proper exposure is equally critical.
At the Dream House, each 18-inch-long shingle shows just 5 1/2 inches.
"That way, every square inch of the roof has triple coverage,"
says Chizmar.
Special measures are also required to keep the shingles from trapping
water, which even in cedar can promote rot. "Nailing cedar
shingles directly to plywood sheathing is the biggest mistake you
can make," says T.O.H. contractor Tom Silva. "I’ve
seen roofs installed that way. They start to go bad right away and
need replacing in 10 years."
Traditionally, shingles were – and sometimes still are –
installed on skip sheathing: boards, usually 1x4s or 1x6’s,
nailed at 1- to 2-inch intervals across the rafters. The gaps between
the boards help wet shingles dry out. But without a solid skin of
plywood topped by roofing felt, aka tar paper, any leaks in the
shingles instantly dribble into the house. So the modern alternative
– and the one being used at the Dream House – is to sheathe
with plywood, cover it with 30-pound felt and then tack down sheets
of a special drainage mesh. Widely known by its brand name, Cedar
Breather, the mesh resembles the open-weave plastic used to scrub
nonstick cookware. Though just 1/4 inch thick and seemingly insubstantial,
it mightily resists compression: A 200-pound man can’t flatten
it. But does it work? "I’ve had good luck with it,"
says Tom. "Since I started using it five years ago, I’ve
kept track of those projects, and I have yet to see any signs of
premature aging."
Regardless of the roofing being used, the eaves, valleys and ridges
always need special protection. At the Dream House, a 3-foot-wide
waterproof membrane protects eaves and rakes from leaks caused by
ice dams and wind-driven water. Wide sheets of 20-gauge copper flashing
line the valleys, while short bent pieces of copper, called step
flashing, interleave between shingles wherever one of the 15 dormers
meets the roof. Narrow copper strips, called drip edges, keep water
away from fascia trim.
Ridges are one of the trickiest details, says Tom. "It’s
best to use a ridge vent, not a gable vent. But a cedar cap on top
of a ridge vent can fail, so I like to put on a copper cap instead.
Then you can cover it with cedar boards, but I think the exposed
copper on top of the cedar looks great."
After the felt, mesh, membrane and flashing are in place, each shingle
is secured with two nails or staples placed about 1 inch from the
sides and roughly 2 inches above the line, called the butt line,
that will be formed by the next higher course. Nails should be aluminum
or galvanized or stainless steel, ring-shanked and long enough to
penetrate the sheathing by at least 3/4 inch. The Dream House crew
uses galvanized 6d ring shanks, which are 1 1/2 inches long. If
staples are used, they should be stainless steel or otherwise corrosion
resistant. Each fastener should be driven flush but not so vigorously
that it crushes the wood. "You want the shingle to be able
to move a little," says Tom. "Otherwise it can split."
As the ruddy rows of shingles spread across his roof, Cromwell sets
aside practical considerations for the moment and just admires the
view. "This house has a kind of romantic, by-the-seashore feel
to it, and I think the cedar fits right in with that," he says.
"But good as it looks now, in a year it will be grayed out
and really beautiful. Most other roofing materials just break down
over time. With cedar, the older it gets, the better it looks."
[Reprinted
through the courtesy of the editors of THIS OLD HOUSE Magazine 1999
Time Publishing Ventures, Inc. THIS OLD HOUSE and the THIS OLD HOUSE
Window are registered trademarks of the WGBH Educational Foundation.
Used with permission.]
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