Page 452 - 2018_IRC

ROOF-CEILING CONSTRUCTION

R804.3.7.2 Roof diaphragm. A roof diaphragm shall SECTION R806
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be provided by attaching not less than / -inch (9.5 mm) ROOF VENTILATION
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wood structural panel that complies with Section R803 R806.1 Ventilation required. Enclosed attics and enclosed
to roof rafters or truss top chords in accordance with rafter spaces formed where ceilings are applied directly to the
Table R804.3. Buildings with 3:1 or larger plan aspect underside of roof rafters shall have cross ventilation for each
ratio and with roof rafter slope (pitch) of 9:12 or larger separate space by ventilating openings protected against the
shall have the roof rafters and ceiling joists blocked in entrance of rain or snow. Ventilation openings shall have a
accordance with Figure R804.3.7.2. least dimension of / inch (1.6 mm) minimum and / inch
1
1
4
16
R804.3.8 Roof tie-down. Roof assemblies shall be con- (6.4 mm) maximum. Ventilation openings having a least
1
nected to walls below in accordance with Table R804.3. A dimension larger than / inch (6.4 mm) shall be provided
4
continuous load path shall be provided to transfer uplift with corrosion-resistant wire cloth screening, hardware cloth,
loads to the foundation. perforated vinyl or similar material with openings having a
1
1
least dimension of / inch (1.6 mm) minimum and / inch
4
16
(6.4 mm) maximum. Openings in roof framing members shall
SECTION R805 conform to the requirements of Section R802.7. Required
CEILING FINISHES ventilation openings shall open directly to the outside air and
R805.1 Ceiling installation. Ceilings shall be installed in shall be protected to prevent the entry of birds, rodents,
accordance with the requirements for interior wall finishes as snakes and other similar creatures.
provided in Section R702.

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1 / IN. × 33 MIL CONT.
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STRAP LAP 12 IN. WITH
4 NO. 5 SCREWS WHERE
SPLICE REQUIRED
SCREW THROUGH ROOF
SHEATHING TO STRAP
NO. 8 AT 6 IN. O.C.
SHADED AREA INDICATES
2IN. BLOCKING BREAK SHAPE
AT 12 FT O.C.
43 MIL SCREWS THROUGH STRAP
BLKG LENGTH ROOF TO BLKG AND BLKG TO TOP
REQUIRED TO SLOPE OF WALL TRACK FLANGE
LAP WALL TRACK NO. 8 AT 6 IN. O.C.
FLANGE A MIN. TOP
1
1/ IN. TRACK
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NOTE: BLKG SHALL
BE PERMITTED TO
BE ATTACHED TO
OUTSIDE FACE OF
SHEATHING OR PREFERABLY
DIRECTLY TO TRACK
FLANGE PRIOR TO SHEATHING
PLACEMENT AS SHOWN
For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm.
FIGURE R804.3.7.2
ROOF BLOCKING DETAIL

2018 INTERNATIONAL RESIDENTIAL CODE ® 427
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