Asphalt (Fiberglass) Shingle Roof Covering Materials Home Owners Network

Asphalt (Fiberglass) Shingle Roof Covering Materials Home Owners Network

Shingle Roof Covering Description

Shingle roof covering materials discussed in this section are the fiberglass strip shingles used in modern residential construction. Strip shingles are the most common roof covering material in modern residential construction. Roof slopes are shown as x/y where x is the number of vertical units rise and y is the number of

horizontal units run. A 4/12 roof has 4 vertical units rise for every 12 horizontal units run.

Roof Slope Restriction

1. Do not install shingles on roofs with a slope less than () 2/12.

2. Install a double underlayment layer under shingles on roofs with a slope between 2/12 and 4/12.

3. Verify manufacturer’s instructions about minimum roof slope. Some manufacturers do not allow shingle application below 2 ½/12.

Roof Deck Type Restriction

1. Install shingle roof covering only on solid sheathed roofs.

Underlayment Specifications

1. Use at least (≥) 15 pound (per 100 square feet) roofing felt. This is the most common shingle underlayment. Other material, such as modified bitumen sheets, is acceptable. Refer to the IRC for other acceptable underlayment materials.

Underlayment Application for Roof Slopes 4/12 and Greater

1. Begin at the eaves and apply at least (≥) a 36 inches wide strip of underlayment parallel to the eaves.

2. Lap horizontal joints at least (≥) 2 inches with the upper strip over the lower strip.

3. Lap end joints as specified by the shingle manufacturer. End joint laps are usually between 4 and 6 inches.

4. Off set end joints by at least (≥) 6 feet.

5. Use sufficient fasteners to hold underlayment in place. The IRC does not specify fastener type and quantity.

6. Minimize wrinkles and distortions in the underlayment. Wrinkles should not interfere with the ability of the shingle’s sealing strips to seal. Underlayment wrinkles and distortions can appear through the shingles creating a cosmetic issue.

Underlayment Application for Roof Slopes Between 2/12 and 4/12

1. Begin at the eaves and apply at least (≥) a 19 inches wide strip of underlayment parallel to the eaves.

2. Begin again at the eaves and apply at least (≥) a 36 inches wide strip of underlayment.

3. Lap each successive layer at least (≥) 19 inches over the previous layer with the upper layer over the lower layer.

4. Lap end joints at least (≥) 6 inches.

5. Use sufficient fasteners to hold underlayment in place. The IRC does not specify fastener type and quantity.

Underlayment Application in 110+ mph Wind Areas

1. Apply underlayment according to the roof slope.

2. Install corrosion-resistant fasteners according to manufacturer’s instructions and space them along the overlaps at not more than (≤) 36 inches on center.

3. Refer to the IRC for additional requirements in wind speed areas of 120 mph or more.

Underlayment Application in Ice Dam Areas

1. Install ice dam underlayment where there is a history of water backup at the eaves caused by ice. Verify ice dam requirements with the local building official. You need not install ice dam underlayment on unconditioned detached accessory structures.

2. Install either a sheet of self-adhering polymer modified bitumen roofing or at least (≥) two layers of roofing felt cemented together. Begin the ice dam underlayment at the lowest edge of all roof surfaces and extend it at least (≥) 24 inches beyond the exterior wall of the building.

3. Measure distances horizontally, not up the roof sheathing. Begin the 24 inches measurement from the interior side of the wall. Example: if the eaves extend 12 inches, horizontally, from the exterior wall of the building, extend the ice dam underlayment at least (≥) 39 ½ inches, horizontally, from the edge of the eaves (assuming a 24 wall).

1. Install drip edge flashing at eaves and at gable rakes.

2. Use drip edge flashing that extends at least (≥) ¼ inch below the roof sheathing and extends at least (≥) 2 inches up the roof deck.

3. Lap adjacent drip edge pieces at least (≥) 2 inches.

4. Attach drip edge using roofing nails spaced not more than (≤) 12 inches on center.

5. Install underlayment under the drip edge at rakes.

6. Install underlayment over the drip edge at eaves.

Closed-Cut Valley Flashing

1. Install closed valley fl ashing material according to manufacturer’s instructions before installing the shingles. You may use at least (≥) a 36 inches wide strip of smooth roll roofing material as closed valley fl ashing material with at least (≥) 18 inches on each side of the valley or you may use any open valley lining material.

2. Place nails at least (≥) 6 inches away from the valley center line, unless other spacing is approved by the shingle manufacturer.

3. Apply the shingles across one side of the valley at least (≥) 12 inches or as recommended by the shingle manufacturer.

4. Apply shingles from the other direction to before the valley center line and trim the edges as recommended by the shingle manufacturer. Seal the cut shingles in closed-cut valley as recommend by the manufacturer. Sealing the cut shingles is frequently omitted. See illustration on next page.

Open Valley Flashing

1. Install at least (≥) a 24 inches wide strip of metal with 12 inches on each side of the valley. The metal will usually be 0.024 inch thick aluminum or 0.0179 inch thick galvanized steel. You may use other metals. Refer to the IRC.

2. You may install at least (≥) an 18 inches wide roll of mineral surfaced roll roofing under at least (≥) a 36 inches wide roll of the same material as an alternative to the metal valley material.

3. Place nails at least (≥) 6 inches away from the valley center line, unless other spacing is approved by the shingle manufacturer.

Sidewall and Penetration Flashing

1. You may use the base and cap (counter) flashing method when the method is approved by the shingle manufacturer. Use either corrosion-resistant metal (0.019 inch/26 gage) or 77 pound roll mineral roofing for the base flashing and corrosion-resistant metal for the cap flashing.

2. Install flashing at the intersections of a sloped roof and a vertical sidewall. Use fl ashing that is at least (≥) 4 inches wide by 4 inches high. Install kick-out flashing at the end of the vertical sidewall as described in the previous roof flashing section.

3. Install continuous vertical flashing behind siding such as panel and lap siding.

4. Install flashing for brick and masonry veneer and for stucco and artificial veneer as described in Chapter 7.

5. Flash the intersection of a sloped roof and a chimney according to the shingle manufacturer’s instructions. This typically includes base or step flashing covered with counter flashing and includes a cricket for chimneys more than () 30 inches wide.

6. Flash other roof penetrations, such as plumbing and gas vents, according to the shingle manufacturer’s instructions.

7. Flash skylights according to the skylight manufacturer’s instructions.

Fastener Type and Quantity in Standard Conditions

1. Use the type and quantity of fasteners recommended by the shingle manufacturer. Locate nails on the shingle strip precisely as recommended by the shingle manufacturer. Some manufacturers recommend installing nails below the black adhesive seal strip. Other manufacturers leave a gap in the seal strip for installing nails. Do not install nails above the seal strip unless allowed by the manufacturer. Failure to comply with manufacturer’s installation instructions is a code violation and may void the manufacturer’s warranty.least (≥) a ⅜ inch diameter head. Use nails long enough to penetrate into the roof sheathing at least (≥) ¾ inch and completely through any sheathing that is less than () ¾ inch thick.

3. Install at least (≥) 4 nails per shingle strip with a nail at 1 inch from each end and two nails equally spaced in the center of the strip, in wind speed areas less than () 110 mph.

Fastener Type and Quantity in Special Conditions

1. Install additional fasteners as recommended by the shingle manufacturer in wind speed areas greater than () 110 mph and for very steep roof slopes such as Mansard roofs. At least (≥) 6 nails per strip is usually recommended in these conditions, but verify fastening recommendations with the shingle manufacturer.

2. Use shingles labeled on the wrapper as complying with ASTM D3161 in wind speed areas greater than () 110 mph.

Staples as Shingle Fasteners

1. Staples are not mentioned in the IRC as a code approved shingle fastener. Some shingle manufacturers allow staples, but seldom recommend them. Avoid using staples as shingle fasteners in both new construction and when replacing an existing shingle roof.


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