Re-roofing Asphalt Shingles
OVERLAY OR TEAR-OFF FOR ASPHALT SHINGLES?
Due to the fact that we are located in a moderate to severe hail exposure area, new asphalt shingles shall not be installed without first removing the existing coverings.(R907.3)
Roof sheathing shall be checked prior to re-roofing and repaired or replaced if rotted or unsound. Replacement sheathing shall conform to the requirements of the Building Code and manufacturer’s specifications.
Asphalt shingles shall be fastened to a solidly sheathed decking or 1 inch thick nominal wood boards. (R905.2.1)
Asphalt shingles shall in no case be used on roofs with less than 2:12 pitch and require special application on pitches less than 4:12. (R905.2.7)
Asphalt shingles shall be fastened with not less than four nails or approved staples. Nails shall not be less than 12 gauge with 3/8-inch minimum diameter head. Staples shall be not less than 16 gauge with 15/16-inch minimum crown width. Nails or staples shall be of sufficient length to penetrate through roofing material and at least ¾ inch into roof sheathing or through the thickness of the sheathing, whichever is less. Staple crown shall be driven so that it tightly bears against shingle but does not cut shingle surfaces. Crown shall be parallel to long dimension of shingle or per manufacturer specs for a 90 mph wind speed. (R905.2.5- R905.2.6)
For roof pitches of 2:12 to less than 4:12:
Two layers of 15# felt applied shingle fashion. Starting with an 18-inch wide sheet and a 36-inch wide sheet over it at the eaves, each subsequent sheet shall be lapped 19 inches horizontally.
For roof pitches of 4:12 and over:
One layer of 15# felt lapped 2 inches horizontally and 4 inches vertically. End laps shall be offset by 6 feet.(R905.2.7)
An ice barrier that consists of at least two layers of underlayment cemented together or of a self-adhering polymer modifed bituman sheet, shall be used in lieu of normal underlayment and extend from the lowest edges of the roof surfaces to a point at least 24 inches inside the exterior wall line of the building.
Exception: Detached accessory structures that contain no conditioned floor area. (R905.2.7.1)
VALLEY FLASHING/ LINING
Valley lining shall be installed in accordance with the manufacturer’s instructions before applying shingles.(R905.2.8.2)
Sidewall flashing: Flashing against a vertical sidewall shall be by the step-flashing method. (R905.2.8.4) All other flashing against a vertical front wall, as well as soil stack, vent pipe and chimney flashing, shall be applied according to the asphalt shingle manufacturer’s printed instructions. (R905.2.8.4- R905.2.8.5)
Kick out flashing: Flashing used to divert water where the lower portion of a sloped roof stops within the plane of an intersecting wall cladding/siding.
ROOF AND SOFFIT VENTS
Minimum required attic ventilation is one square foot of ventilation in the roof for every 300 square feet of roof or floor area, if there is at least ½ venting in the soffits. If not than there is one square foot of ventilation in the roof for every 150 square feet of roof or floor area.