Oklahoma Administrative Code › Title 748 - Oklahoma Uniform Building Code Commission › Chapter 20 - Adopted Codes › Subchapter 6 - IRC[®] 2018 › Section 748:20-6-13 - IRC[®] 2018 Chapter 8 Roof-Ceiling Construction

Current through Vol. 41, No. 20, July 1, 2024
Chapter 8 of the IRC® 2018 is adopted with the following
				  modifications:
(1) Section R801.3 Roof
				drainage. This section has been stricken from the code.
(2) Section 802.3 Ridge. This section has
				been modified to clarify a ridge beam shall be designed in accordance with
				acceptable engineer practices when the roof load exceeds specific criteria to
				carry one-half of the tributary load. This section has been modified to read:
				R802.3 Ridge. A ridge board used to connect opposing rafters shall be not less
				than 1 inch (25 mm) nominal thickness and not less in depth than the cut end of
				the rafter. Where ceiling joists or rafter ties do not provide continuous ties
				across the structure, a ridge beam shall be designed, in accordance with
				acceptable engineer practices, and supported on each end of the wall or girder,
				when roof loads exceed 10 per square foot pound dead loads and 20 per square
				foot pound live loads. In the case where rafters are used to support roof and
				finished ceiling (also known as a cathedral ceiling) with no connection of
				opposing rafters, ridge beam shall be designed, in accordance with acceptable
				engineer practices to carry one half of tributary load of the roof.
(3) Section R802.4.1 Rafter size. This
				section has been modified to provide guidance for builders framing rafters
				above the top sill of the wall system and provide an exception to require
				collar ties to be sized not less than the required size of the rafters they are
				connected to. This section has been modified to read: 802.4.1 Rafter size.
				Rafters shall be sized based on the rafter spans in Tables R802.4.1(1) through
				R802.4.1(8). Rafter spans shall be measured along the horizontal projection of
				the rafter. For other grades and species and for other loading conditions,
				refer to the AWC STJR. The tabulated rafter spans in Tables R802.4.1(1) through
				R802.4.1(8) assume ceiling joists are located at the bottom of the attic space
				or some other method of resisting the outward push of the rafter on the bearing
				walls, such as rafter ties is provided at that location. Where ceiling joists
				or rafter ties are located higher in the attic space, the rafter span in these
				tables shall be multiplied by the following rafter reduction factors: Where
				ceiling joists or rafter ties are located at one third the span of the rafter
				the adjustment factor is 0.67, at one quarter of the span of the rafter the
				rafter adjustment factor is 0.76, at one fifth the span of the rafter the
				adjustment factor is 0.83, at one sixth of the span of the rafter, the
				adjustment factor is 0.90, and at two fifteenths of the rafter or less, there
				is no need for adjusting the rafter capacity. Exception: Collar Ties.
				Installation of the collar ties to reduce the span of the rafters is permitted
				as shown in Figure R802.4.5. Collar ties shall be installed at every rafter and
				sized not less than the required size of the rafters they are
				connected.
(4) Section R802.4.2
				Framing details. This section has been modified to change the rafter framing
				details. This section has been modified to read: R802.3 Framing details.
(A) Rafters shall be framed to a ridge board
				or to each other with a collar tie, gusset plate or ridge strap in accordance
				with Table R602.3(1). Rafters shall be nailed to the top wall plates in
				accordance with Table R602.3(1) unless the roof assembly is required to comply
				with the uplift requirements of Section R802.11. Ridge board shall not be less
				than 1-inch (25 mm) nominal thickness and not less in depth and one size
				greater than the rafters attached to it.
(B) Where a 1-inch (25 mm) nominal thickness
				ridge is used, all rafters shall be framed not more than 1.5 inches (38 mm)
				offset from each other at the ridge board or if no ridge is used they should be
				framed directly opposite from each other with a gusset plate as a tie. When a
				nominal 2-inch rafter is used they may be offset with no limitations.