20190071 Permit Pkg (4)ROOF ASSEMBLIES
TABLE R905.1.1(2
UNDERLAYMENT APPLICATION
ROOF COVERING
SECTION
MAXIMUM ULTIMATE DESIGN
WIND SPEED, V„ rt < 140 MPH
MAXIMUM ULTIMATE DESIGN
WIND SPEED, V„„ >_ 140 MPH
For roof slopes from two units vertical in 12
units horizontal (2:12), up to four units vertical
in 12 units horizontal (4:12), underlayment shall
be two layers applied in the following manner:
apply a 19 -inch strip of underlayment felt paral-
lel to and starting at the eaves. Starting at the
eave, apply 36 -inch -wide sheets of underlay-
ment, overlapping successive sheets 19 inches.
Distortions in the underlayment shall not inter-
Same as Maximum Ultimate Design Wind Speed,
Asphalt shingles
R905.2
fere with the ability of the shingles to seal.
V„1< < 140 mph except all laps shall be not less
For roof slopes of four units vertical in 12
than 4 inches.
units horizontal (4:12) or greater, underlayment
shall be one layer applied in the following man-
ner: underlayment shall be applied shingle fash-
ion, parallel to and starting from the eave and
lapped 2 inches, Distortions in the underlayment
shall not interfere with the ability of the shingles
to seal. End laps shall be 4 inches and shall be
offset by 6 feet.
For roof slopes from two and one-half units ver-
tical in 12 units horizontal (21/2:12), up to four
units vertical in 12 units horizontal (4:12), under-
layment shall be a minimum of two layers applied
as follows: starting at the eave, apply a 19 -inch
strip of underlayment parallel with the eave.
Starting at the eave, apply 36 -inch -wide strips of
Same as Maximum Ultimate Design Wind
Clay and concrete tile
R905.3
underlayment felt, overlapping successive sheets
Speed, Vu„ < 140 mph except all laps shall be not
19 inches.
less than 4 inches.
For roof slopes of four units vertical in 12 units
horizontal (4:12) or greater, underlayment shall
be a minimum of one layer of underlayment felt
applied shingle fashion, parallel to and starting
from the eaves and lapped 2 inches. End laps shall
be 4 inches and shall be offset by 6 feet.
Metal roof shingles
R905.4
For roof slopes from two units vertical in 12
units horizontal (2:12), up to four units vertical
in 12 units horizontal (4:12), underlayment shall
Mineral -surfaced roll
R9055
be two layers applied in the following manner:
roofing
.
apply a 19 -inch strip of underlayment felt paral-
lel to and starting at the eaves. Starting at the
Slate and slate -type
R905.6
eave, apply 36 -inch -wide sheets of underlay -
shingles
Apply n accordance with the manufacturer's
PPYi
installation instructions.
ment, overlapping successive sheets 19 inches,
and fastened sufficiently to hold in place.
Wood shingles
R905.7
For roof slopes of four units vertical in 12
units horizontal (4:12) or greater, underlayment
shall be one layer applied in the following man -
Wood shakes
R905.8
ner: underlayment shall be applied shingle fash-
ion, parallel to and starting from the eave and
lapped 4 inches. End laps shall be 4 inches and
Metal panels
P
R905.10
shall be offset by 6 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
2015 INTERNATIONAL RESIDENTIAL CODE® 415