The following is about what you didn’t know about roof installation from Tom Silva, the General contractor of the Ask This Old House Video.
Roof installation requires you to be equipped. Make sure you are supported by lines attached to the ridge and stage-ins surrounded by safety rails.
The supports will prevent you from falling and becoming a part of the statistics where a third of construction workers die from falling off the roof.
Begin your roof installation from the edge using an aluminum drip edge that’s around 8 inches wide. The aluminum has a kicker that will guide the water droplets away from running over the fascia board and causing it to rot over time. The gap between the kicker and the fascia board can be half an inch.
Secure the aluminum drip edge on all the sides including the gable ends using 1 ¼” galvanized roofing nails. If your building will be unheated there will be no self ceiling. In that case, a 30-pound felt paper to cover the entire roof can be used. The felt paper acts as relief between the roof sheath and the underside of the shingles. It will absorb moisture in case it builds up to avoid tampering with the roof sheath.
Layout the standard 3-tab shingle that’s 36” wide and 12” high. The shingle has sections made of tar that is activated by the hot sun. When heated, the tar glues to the lower part of the tab to the shingle preventing it from being blown out.
Before nailing the shingles, mark horizontal lines that are 5” apart for the reveal (exposure) and vertical lines spaced 6” apart to help you place the shingles accurately. Place the shingles overlapping each other by 6”. Starting from the edge, leave an overlapping allowance of ½” to accommodate surface tension. Nail all your shingles accurately across the roof to the ridge. At the ridge place well-cut pieces to overlap on either side of your roof.