Starting Out Right The efficiency of the job and the longevity of the roof depend on carefully laying down the starter courses along the eaves. To prevent ice dams up here in snow country, we first run out a 36-inch-wide layer of AC EavesSeal (NEI, 50 Pine Rd., Brentwood, NH 03833; 800/998-4634; www.nei-act.com). Intended for reroof work, this membrane has a 4-inch-wide self-adhesive leading edge that adheres to the new drip edge; the top edge is nailed (Figure 3). Figure 3. To guard against damage from ice dams, a 36-inch-wide strip of bituminous membrane is rolled out along the eaves. After lightly nailing the top edge, the membrane’s 4-inch-wide adhesive strip is pressed onto the new drip edge to form a tight seal.

Efficient layout.

While the membrane is being applied, my crew chief will "map out" the roof to find the most efficient and most attractive layout for the shingles. Many roofers simply start at the rake edge with a full shingle and let the tabs fall where they may. I do the same with architectural shingles, because there are no tabs to align. But with tabbed shingles, I prefer to shingle outward from a pair of vertical center lines. This not only enables me to keep two people nailing without tripping over each other, it assures me that the shingle tabs will align vertically because they won’t be affected by any waviness in the rake edge. It also means the shingles on the ends of each course will be close to the same width. We do, however, measure back to the rake edges and to any dormers, skylights, or chimneys to make sure we won’t end up with skinny tabs, which invariably break off and look terrible. After making any adjustments back and forth, we snap the center line, then a second, parallel line 6 inches over — it doesn’t matter which side. To create a stepped pattern, succeeding courses will alternate between these lines as we work our way up the roof.

Butting up.

For the new roof to lay flat, the top edges of the new shingles must butt up against the tabs of the old ones . The trick is to use precut "invert" shingles as filler strips. Beginning at one vertical chalk line, we use 5-inch-wide "inverts," tar spots pointed towards the eaves, and align the bottom edge with the drip edge. This course gets nailed at the bottom, just above the tar spots. The first full course is aligned with the second chalk line. Because earlier we cut the top layer of existing shingles back 12 inches from the eaves, we can run full-width shingles, overlaying the inverts and laid flush with the drip edge. The second full-width course of shingles is laid out back at the first chalk line and butted up against the bottom edge of the fourth course of old shingles. We butt up succeeding courses until we get above the 36-inch-wide eaves membrane, at which point we can really fly.

Pyramid pattern.

Despite the manufacturers’ assurances, we find that shingle sizes are inconsistent. To ensure straight vertical lines, and to avoid that wavy pattern you see when material varies from bundle to bundle, we lay our shingle courses in a pyramid shape . We start by running one column of three-tab shingles nearly all the way up to the ridge, alternating each course back and forth between the two chalk lines. Returning to the bottom, we cover a triangular area on each side of the column, stacking six courses of three-tab, two-tab, and one-tab shingles. Next, we fill in with full shingles until our courses reach the top of the pyramid, then we repeat the procedure.

Reroof nailing.

On an average job, we run three air nailers off one Emglo gas-powered compressor (Emglo Air Compressors, 303 Industrial Park Rd., Johnstown, PA 15904; 814/269-1000) that we leave on the ground. To keep the hoses from tangling, we run one thick lead hose from the compressor to the roof and branch off from there. We use standard round head roofing nails in our guns, 11/2 inches long when we’re covering one layer of old roofing, 13/4 inches for two layers. Condensation forms on the tips of nails that protrude into attics, so I try to use the shortest nails possible. We follow standard nailing patterns — four nails per shingle with the two center nails located just above the cutouts. The exception is at the edges, where we hold our nails back 11/2 inches instead of the 1 inch called for by roofing manufacturers. Shingles are nailed with pneumatic coil nailers. Because the existing roof has some give to it, nails are held back 11/2 inches from the shingle edges to avoid creating dips that can be seen from the ground. We do this because we are nailing over a resilient surface, and when the nails are placed too close together they can make a depression that can be seen from the ground. There is no disadvantage to spreading the nails out as little as we do. Valleys. Before our shinglers reach a valley, we flash it with a 36-inch-wide layer of 90-pound mineral-surfaced roll roofing. If it’s a full-length valley, we lap the flashing over the eaves membrane and run it to the drip edge. If it’s a dormer, we run the flashing past the beginning of the valley and lap it over the new shingles in the course below. When it comes to shingling a valley, I prefer the closed-cut approach because it offers the best combination of protection and efficiency. To make a closed-cut valley, we run up all the shingles for one side, making sure they extend at least one full tab (12 inches) past the centerline of the valley (Figure 6). Figure 6. Valleys are first flashed with 90-pound roll roofing. Then shingles from one roof plane are laid so they extend one tab beyond the valley center. Shingles from the other roof plane are overlaid, then cut back with a hooked knife to form a "closed" valley. We also make sure to keep all of our nails at least 8 inches back from the center. When we do the other side, we run all the shingles far enough so that we can snap a chalk line through the center of the valley and cut a nice straight line with a hooked roofing blade. When we do a dormer, we always run up the dormer shingles first so the water from the main roof can’t run under the dormer shingles.

Permanent flashing.

When I was young and foolish, I used to take pride that I cared enough to cut loose all the old step flashing and reweave it into the new roofing. It cost a lot of money to do that, and the homeowners never noticed it, so I stopped. The truth is, as long as the flashing was done right the first time and hasn’t rotted away, it’s better left in place. When we shingle up to dormers, chimneys, or skylights, we still peel up the bottom edge of the flashing and tuck the new roofing underneath. Then, as we work our way up the sides, we bed each shingle down onto a thick bead of roof cement along the edge where the shingle meets the wall line. We also lay a large bead of tar under the shingles where they meet the head flashing. Contrary to popular belief, as long as the cement is covered by the roofing, it will serve for the life of the roof.

Capping Off

When we reach the top of the roof, we fold the last courses over the ridge and cover them with cap shingles. To ensure a straight line, we measure down 6 inches from the center of the ridge on the most visible side, and snap a line. We run cap shingles from one end of the roof to the other, aligning the edges with the chalk line, and placing one nail on either side of the ridge, just behind the tar strip, which will be covered by the next shingle. The final cap will be a 5-inch piece or less, and we cover the exposed nails with tar.

Ventilation.

When the attic needs more ventilation, I like to install a low-profile shingle-over ridge vent, because it does the job, yet blends into the roofline. We like either the Omni-Ridge (Lomanco, P.O. Box 519, Jacksonville, AR 72076; 800/643-5596; www.lomanco.com) or the ShingleVent II (Air Vent, 4801 N. Prospect Rd., Peoria Heights, IL 61614; 800/247-8368), because they both have an external baffle that keeps snow and driven rain out of the attic. After the roofing and sheathing are cut out, we hold the ridge vent to the same chalk line as the caps and nail it in place. We run cap shingles over the top of the vent, using 21/2-inch roofing nails to reach the sheathing.

Customer Satisfaction

No job is successful unless the customer is satisfied. At the end of every day, we sweep up the site and pick up nails from the driveway and short grass with a Magnet Nail Sweeper (Hilco, P.O. Box 1789, Hickory, NC 28603; 704/328-8141). When the job is finished, we do a final sweep from the ridge down with a wide soft-bristle broom. We also clear roof debris from the gutters and thoroughly sweep the driveway, front steps, walkways, and anywhere else debris may have settled. We want it to look like we were never there, so we make sure to put anything that we had to move back in its place. Finally, before the last ladder is taken down, I take a can of black or aluminum and paint the vent pipes, chimney flashing, and furnace flange. This not only makes my work look its best on the day I leave the job, but it prevents rust stains from making my work look bad in the future. John Curran and his wife, Jan, own and operate RSI General Contractors, a Syracuse, N.Y., roofing, siding, and insulation company founded in 1978.