From the Ground Up: Roofing and Siding

Nothing is as important to the look of a house as roofing and siding. Take two identical wood-frame houses, for example. Finish one in white clapboard with a cedar shake roof and the other in pink stucco with a clay tile roof, and you've made some major—and very different—aesthetic statements.

But there's more to these choices than appearances. Roofing and siding are also a house's first line of defense against the weather. That's why the materials have to be durable, properly installed, and well maintained. Traditional options—wood, brick, stone, and stucco for walls; cedar, slate, and tile for roofs—are time-tested and good-looking. They're also pricey. So in recent decades they've been joined by man-made look-alikes that cost less and don't need as much upkeep.

"You used to have to choose between low-maintenance and nice-looking," says Tom Silva, This Old House general contractor. "Today you can have both." Read on for Tom's installation techniques and a look at the next generation of roofing and siding products.

A Many-Layered Thing

No roofing or siding material by itself is a perfect barrier against the elements. So before the outer skin goes on, Tom Silva protects all the vulnerable areas — the corners and edges — with sticky strips of waterproofing membrane. Then he tops everything with layers of builder's felt, a thick, asphalt-impregnated paper.

What, No Housewrap?
The plastic housewrap under the siding of most new houses or additions is meant to stop wind and water. But Tom uses the old (and much cheaper) materials — builder's felt or rosin paper — because he prefers to insulate with spray foam. "There's no air or moisture passage to worry about," he says. And always, whether over felt, paper, or a wrap, Tom tacks up drainage strips before he hangs wood siding. "It needs an air space behind so it can dry out."

Roofing and Siding Materials

Peel-and-Stick Flashing
Of all the new building materials that Tom has seen in the past 25 years, he's embraced none more enthusiastically than self-adhesive waterproofing membrane. This peel-and-stick high-tech tar is impervious to water and literally seals itself around any fasteners that penetrate it. The membrane also sticks tenaciously to itself, so installation can be tricky. "We learned not to install it in the wind," Tom says. Tough as it is, the membrane does have an Achilles' heel—sunlight—so it must always be covered with siding, roofing, or metal flashing.

Cement Siding
Fiber-cement siding is virtually indistinguishable from painted wood, yet it never rots, won't burn, extends the life of a paint job, and is warranted for 50 years. And the price—about $3 per square foot, installed and painted—is slightly less than that of most wood clapboard. The siding, a mix of cement, cellulose fiber, and sand, was used on the Billerica TV project house. Tom was impressed. "It looks really nice," he says.

Plastic Trim
Cellular PVC, an extrusion of solid vinyl whipped full of tiny bubbles, can be cut, routed, nailed, and painted just like real wood. In fact, it does everything wood does—except rot, check, warp, or fade. Tom used it on the outside of the Concord cottage project, and even Norm Abram was hard pressed to tell that it wasn't painted wood.

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