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Roofing for an addition generally duplicates that on the house. In most cases it consists of sheathing of 0.5-inch plywood; roofing felt; flashing at edges and valleys, best made of aluminum; and the same type of shingles used for the house. When the unit rise of the addition roof is less than 2, hire a professional to install roll roofing instead of shingles. Any addition roof must be flashed at newly created joints, as depicted below. Buying the Right Roofing: Matching new roofing material to old can be tricky, if only because old roofing changes color as it weathers. Also, you may encounter an unusual installation pattern in asphalt shingles that is difficult to replicate. If you cannot make a good match, consider a new roof for the house. Diverting Rainwater: Gutters are useful on any roof, but especially so in the case of an intersecting gable, where there is a heavy flow of water from the valleys between the main and addition roofs. Ex tend gutters around the addition or, if necessary, install gutters on both roofs. CAUTION---Consult the EMERGENCY GUIDE for advice on dealing with asbestos shingles when cutting or removing them. SAFETY TIPS---Work gloves keep hands safe from sharp flashing edges. TOOLS:
MATERIALS
LEAKPROOFING JOINTS Flashing a shed roof. 61--- • Sheathe the roof, leaving a 1-inch gap at the wall to permit ventilation. Add drip edges, felt underlayment, and roofing, then nail flow-through ventilating material over the gap. • Bend flashing to fit under the siding where it was cut for the rafter plate and over the ventilating material; a plywood jig can help. • Slip the flashing into place. • Nail through the siding and flashing at 12-inch intervals. Seal the joint in between with roofing caulk. • In brick siding, use a circular saw with a masonry blade to cut a groove 0.5 inch deep into a horizontal mortar joint about 6 inches above the roof. • Bend flashing as above and fasten it to the wall below the groove with masonry nails driven into a mortar joint. • Fit a second strip—known as counterflashing—into the groove. Bend it over the first strip, making sure to cover the nailheads. Secure it with masonry nails hammered into the groove every 2 feet, then caulk the groove. 61 TRICKS of the TRADE --- Tidy Bends in Metal Flashing 62a--- When a long strip of flashing must be bent, as for a shed-roof addition, you can shape a uniform angle with a plywood jig like the one shown here. Fold a piece of flashing to the desired angle, trace it on a piece of plywood, and then add inch to the width and to each end. Cut out the penciled shape and nail the plywood to 2-by-4 stakes. Then have a helper feed flashing into the cut as you pull it through from the other side of the jig. Flashing a gable roof at a wall. 62b--- To seal the joints at the edge of this roof, place flashing under each course of shingles as you install them. • Start the job by attaching sheathing, drip edges, and felt, as well as vents at the ridge or in the gable. • Lay a first course of shingles with the tabs removed. Cover the end with a rectangle of flashing bent to fit under the siding where it was cut for the rafter plate. Nail the upper corner of the flashing to the roof. • Lay a second course of full shingles directly atop the first, covering the flashing. • As you shingle toward the peak, cover at least the 2 upper inches of each course with a rectangle of flashing. • At the roof peak, attach two precut pieces: one folded over the ridge and ex tending up the wall on each side, the other piece extending down the wall over the first and onto the peak. • Apply roofing caulk where the strips of flashing overlap each other. For brick siding, install counter-flashing in a groove parallel to the rafters. Slip the rectangles under the counterflashing. 62 Flushing an intersecting roof. 63a--- Special valley flashing shaped like a W in cross section and fitted for nailing cleats protects valleys between roofs. • Before shingling the addition roof, use a utility knife with a hooked blade (photo graph) to cut the house roofing back 3 inches from the center of each valley; pull roofing nails within 7 inches of the centers. Remove about 2 square feet of shingles above the peak of the addition roof and set aside for reuse; you may choose to remove the cut shingles also. • Working from the addition side of each valley, slip the flashing in place. At tach cleats every 4 feet, lifting shingles as needed. Nail the cleats to the sheathing. • Trim the flashing 1 foot above the peak of the valleys, hammer it flat to the roof, and replace the shingles you removed. ADDING GUTTERS Running around a corner. 63b--- To reinstall the existing gutters, add a corner piece to each end that was cut away for the addition, and extend the gutter along the new fascia. Place downspouts at the outside corners; if water overflows the gutter at a valley, install an extra downspout there. |
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Tuesday, April 1, 2014 1:09 PST