Reroofing with Asphalt Shingles

Check your local codes to see how many layers of roofing your roof can handle. In most cases, if a roof has only one or two layers of roofing, it can be reroofed simply by installing new shingles on top of the old ones. If your roof already has multiple layers of shingles, a “tear-off job is needed: All the roofing and felt (and perhaps the flashing) must be removed. This is a demanding and very messy job. Buy a roofing spade for removing shingles.

Asphalt shingles come in many colors, shapes, textures, and qualities. They are sold by the square—the amount of material needed to cover 100 square feet. In the long run, it is well worth the extra cost to buy shingles that are guaranteed for 30 years. You’ll save plenty of backbreaking work if you pay extra for the roofing materials to be delivered via a conveyor belt up onto the roof. Use nails long enough to penetrate the sheathing; the length will depend on the thickness of the old and new roofing. Use your old shingles as guides and you’ll find that a reshingling project can go quickly. Before you begin, nail all loose or curled shingles, and replace any that are missing. Reset any popped nails. A roofing hammer has a guide that allows you to quickly position shingles at the right height above the course below.

Tools: Regular or roofing hammer, utility or roofing knife, chalk line, speed square, pry bar, ladder.

1. Replace drip cap. Check drip-edge flashing at the eaves and rakes. If it is failing, replace as you would any other flashing . Also check fascia boards and replace any rotted pieces.

2. Set flashing in valleys. Use sheet-metal flashing for valleys. Position the flashing so it rests firmly on the roof, then attach with nails near the edges. Valley flashing should project about 1 inch beyond the eaves. Snap chalk lines on both sides of the center, angled outward at a rate of 1 inch per 8 feet.

3. Lay a starter course. Purchase a starter strip, which is a continuous roll about half the width of shingles. Or make starter strips by trimming shingles to the width of the old exposure— usually 5 inches. Nail the starter strip at the eaves.

4. Start the first course. Shingles measure 1x3 feet, with cutouts that divide the shingle into three tabs. Simply butt each new shingle against the bottom edge of an old one, staggering the tabs. Always stagger end joints from one course to the next.

5. Position the shingles. Build courses stair-step fashion. The first course will have only a 3- or 4-inch exposure, but a gutter will conceal this. Small slits in the top of the shingles will help you align the courses to produce a consistent-looking pattern. At the gable end, cut each piece to overhang by about an inch. Or let the pieces “run wild”; later, snap a chalk line along the vertical edge and cut the line with a utility knife.

6. Nail the shingles. After the first course, the exposure will be about 5 inches. Each shingle requires four nails, placed about 1/2 inch above the cutouts. Do not sink the nailheads so far that they bite into the surface of the shingle. When the sun heats the roof, it will melt the adhesive spots in the shingles and adhere them together.

7. Flash a chimney. Add new chimney flashing as you apply the roof; some pieces are installed on top of the shingles, while others rest on top of one shingle and under another. A cant strip at the base of a vertical surface improves runoff.

8. Shingle the ridge. Cover the ridge of the roof with special ridge shingles, or cut ordinary shingles into three separate tabs to fit. Overlap the ridge shingles to conceal the nails, leaving about a 5-inch exposure. The last nails will be exposed; cover them with dabs of roofing cement.

Roofing Tips

■ If your area is subjected to high winds, make sure that the starter strip and first course are nailed down well.

■ When installing shingles on top of valley flashing, snip a 2-inch triangle out of the upper corner of the shingle (which will be covered). This helps ensure that wind-driven rain cannot sneak up and under the protective flashing.

■ Work when the weather is warm so that the shingles can adhere to each other. Do not work in very hot weather or you could damage the shingles.

Reroofing with Wood Shingles and Shakes

Wood shingles and shakes are often installed on spaced sheathing—that is, 1x4s or 1x6s that are laid across rafters with 2-to 4-inch spaces between them. This arrangement provides air circulation that allows the wood to dry out. Building codes in some climates may permit installing wood shingles on top of solid sheathing, or even directly over asphalt shingles. Check with your local building department.

Wood roofing works best if the roof has at least a 6-in-12 pitch (a 6-inch rise in the slope of the roof for every 12 inches of horizontal run). It may not provide adequate protection for a flatter roof. To lay wood shingles and shakes, use many of the same basic techniques as for asphalt shingles. You’ll need a couple more tools and a little more preparation work, though. Additional tools include a multipurpose roofer’s hammer for nailing, trimming, and gauging courses, and a lightweight power saw for more precise cutting.

Purchase the best shingles or shakes you can afford. Buy flashings made for use with wood shingles or shakes. Use nails made for wood roofing and long enough to penetrate the total thickness of the roof plus the sheathing. If you pay extra for delivery of materials to your rooftop, you will save your energy for the actual roofing work.

Tools: Roofer’s hammer, utility knife, lightweight power saw, pry bar, ladder.

1. Install the shingles. Apply roofing felt as recommended by your local building department. Start a wood shingle roof with a double starter course, projecting over the edges by an inch. This will ensure that rainwater flows into a gutter rather than behind it. Stagger the joints of succeeding courses. There should be a 7>-inch gap between shingles or shakes on each side. It is important that the gaps of succeeding courses be offset by at least an inch. Drive two nails per shingle, about 1 inch from each edge. Make sure that all the nailheads are covered by the shingles of the next course.

2. Flash a valley. Flash valleys with 18-gauge W-metal galvanized flashing made for shingle or shake roofing. Cut the shingles or shakes so their edges are about 3 inches away from the center of the flashing. Avoid having any roofing pieces narrower than 4 inches.

Shake and Shingle Exposure - In a typical installation, shakes 18 inches long are overlapped 10 inches, leaving an exposure of 8 inches. Shakes 24 inches long are often overlapped 14 inches, for an exposure of 10 inches. These arrangements ensure that the roof is covered by at least two layers of roofing at all points. If you overlap 18-inch shakes by 12 inches or 24-inch shakes by 16 inches, you will have three-layer protection, which may be recommended in areas with severe weather.

3. Roof the ridge. Cover the ridge with overlapped 1x4 or 1x6 boards. Caulk the overlap to prevent leakage. Alternatively, purchase hip shakes, which are about 12 inches long and have beveled edges for a more finished look. Attach the ridge caps with extra-long nails that penetrate the sheathing.

Roof with shakes. Install shakes the same way as wood shingles but interweave 18-inch-wide strips of 30-pound roofing felt as shown above. Install a layer of roofing felt, then a course of shakes, then another layer of felt, and so on. The bottom of each row of felt should be positioned so it is just covered by the two courses of shakes above (otherwise, it would show in the gaps between shakes).

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