Page 460 - 2018_IRC

ROOF ASSEMBLIES

TABLE R905.1.1(3)
UNDERLAYMENT ATTACHMENT
MAXIMUM ULTIMATE DESIGN MAXIMUM ULTIMATE DESIGN
ROOF COVERING SECTION
WIND SPEED, V ult < 140 MPH WIND SPEED, V ult  140 MPH

Asphalt shingles R905.2
The underlayment shall be attached with corrosion-resistant
fasteners in a grid pattern of 12 inches between side laps with
a 6-inch spacing at side and end laps.
Underlayment shall be attached using metal or plastic cap
nails or cap staples with a nominal cap diameter of not less
than 1 inch. Metal caps shall have a thickness of not less than
Fastened sufficiently 32-gage sheet metal. Power-driven metal caps shall have a
Clay and concrete tile R905.3
to hold in place minimum thickness of 0.010 inch. Minimum thickness of the
outside edge of plastic caps shall be 0.035 inch. The cap nail
shank shall be not less than 0.083 inch for ring shank cap nails
and 0.091 inch for smooth shank cap nails. Staples shall be
not less than 21 gage. Cap nail shank and cap staple legs shall
have a length sufficient to penetrate through the roof sheath-
3
ing or not less than / inch into the roof sheathing.
Photovoltaic R905.16 4

Metal roof shingles R905.4

The underlayment shall be attached with corrosion-resistant
Mineral-surfaced roll R905.5 fasteners in a grid pattern of 12 inches between side laps with
roofing a 6-inch spacing at side and end laps.
Underlayment shall be attached using metal or plastic cap
Slate and slate-type R905.6 nails or cap staples with a nominal cap diameter of not less
shingles than 1 inch. Metal caps shall have a thickness of not less than
Manufacturer’s installation 32-gage sheet metal. Power-driven metal caps shall have a
instructions. minimum thickness of 0.010 inch. Minimum thickness of the
Wood shingles R905.7 outside edge of plastic caps shall be 0.035 inch. The cap nail
shank shall be not less than 0.083 inch for ring shank cap nails
and 0.091 inch for smooth shank cap nails. Staples shall be
not less than 21 gage. Cap nail shank and cap staple legs shall
Wood shakes R905.8 have a length sufficient to penetrate through the roof sheath-
3
ing or not less than / inch into the roof sheathing.
4
Metal panels R905.10

For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.447 m/s.

2018 INTERNATIONAL RESIDENTIAL CODE ® 435
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