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SECTION R802 WOOD ROOF FRAMING

R802.1 Identification.
Load-bearing dimension lumber for rafters, trusses and ceiling joists shall be identified by a grade mark of a lumber grading or inspection agency that has been approved by an accreditation body that complies with DOC PS 20. In lieu of a grade mark, a certificate of inspection issued by a lumber grading or inspection agency meeting the requirements of this section shall be accepted.

Exception:
Dimension lumber which is neither identified by a grade mark nor issued a certificate of inspection by a lumber grading or inspection agency may be used for load bearing purposes under the following conditions when authorized by the authority having jurisdiction:

1.    The producing mill shall sell or provide the lumber directly to the ultimate consumer or the consumer's contract builder for use in an approved structure.
2.    The producing mill shall certify in writing to the consumer or contract builder on a form to be provided by the authority having jurisdiction that the quality and safe working stresses of such lumber are equal to or exceed No. 2 grade of the species in accordance with the conditions set forth in American Softwood Lumber Standard (PS 20-99) published by the United States Department of Commerce. Such certification shall be filed as part of the building permit application.
R802.1.1 Blocking. Blocking shall be a minimum of utility grade lumber.
R802.1.2 End-jointed lumber. Approved end-jointed lumber identified by a grade mark conforming to Section R802.1 may be used interchangeably with solid-sawn members of the same species and grade.
R802.1.3 Fire-retardant-treated wood. Fire-retardant- treated wood is any wood product which, when impregnated with chemicals by a pressure process or other means during manufacture, shall have, when tested in accordance with ASTM E84, a listed flame spread index of 25 or less and show no evidence of significant progressive combustion when the test is continued for an additional 20-minute period. In addition, the flame front shall not progress more than 10.5 feet (3200 mm) beyond the center line of the burners at any time during the test.
R802.1.3.1 Labeling. Fire-retardant-treated lumber and wood structural panels shall be labeled. The label shall contain:
1.    The identification mark of an approved agency in accordance with Section 1703.5 of the Building Code of New York State.
2.    Identification of the treating manufacturer.
3.    The name of the fire-retardant treatment.
4.    The species of wood treated.
5.    Flame spread and smoke developed rating.
6.    Method drying after treatment.
7.    Conformance with appropriate standards in accordance with Sections R802.1.3.2 through R802.1.3.5.
8.    For FRTW exposed to weather, damp or wet location, the words “No increase in the listed classification when subjected to the Standard Rain Test” (ASTM D2898).
R802.1.3.2 Strength adjustments. Design values for untreated lumber and wood structural panels as specified in Section R802.1, shall be adjusted for fire retardant- treated wood. Adjustments to design values shall be based upon an approved method of investigation which takes into consideration the effects of the anticipated temperature and humidity to which the fire-retardant-treated wood will be subjected, the type of treatment and redrying procedures.
R802.1.3.2.1 Wood structural panels. The effect of treatment and the method of redrying after treatment, and exposure to high temperatures and high humidities on the flexure properties of fire-retardant-treated softwood plywood shall be determined in accordance with ASTM D 5516. The test data developed by ASTM D 5516 shall be used to develop adjustment factors, maximum loads and spans, or both for untreated plywood design values in accordance with ASTM D 6305. Each manufacturer shall publish the allowable maximum loads and spans for service as floor and roof sheathing for their treatment.
R802.1.3.2.2 Lumber. For each species of wood treated the effect of the treatment and the method of redrying after treatment and exposure to high temperatures and high humidities on the allowable design properties of fire-retardant-treated lumber shall be determined in accordance with ASTM D 5664. The test data developed by ASTM D 5664 shall be used to develop modification factors for use at or near room temperature and at elevated temperatures and humidity in accordance with an approved method of investigation. Each manufacturer shall publish the modification factors for service at temperatures of not less than 80°F (26.7°C) and for roof framing. The roof framing modification factors shall take into consideration the climatological location.
R802.1.3.3 Exposure to weather. Where fire-retardant-treated wood is exposed to weather, or damp or wet locations, it shall be identified as “Exterior” to indicate there is no increase in the listed flamespread index as defined in Section R802.1.3 when subjected to ASTM D 2898.
R802.1.3.4 Interior applications. Interior fire-retardant-treated wood shall have a moisture content of not over 28 percent when tested in accordance with ASTM D 3201 procedures at 92 percent relative humidity. Interior fire-retardant-treated wood shall be tested in accordance with Section R802.1.3.2.1 or R802.1.3.2.2. Interior fire-retardant-treated wood designated as Type A shall be tested in accordance with the provisions of this section.
R802.1.3.5 Moisture content. Fire-retardant-treated wood shall be dried to a moisture content of 19 percent or less for lumber and 15 percent or less for wood structural panels before use. For wood kiln dried after treatment (KDAT) the kiln temperatures shall not exceed those used in kiln drying the lumber and plywood submitted for the tests described in Section R802.1.3.2.1 for plywood and R802.1.3.2.2 for lumber.
R802.1.4 Structural glued laminated timbers. Glued laminated timbers shall be manufactured and identified as required in AITC A190.1 and ASTM D3737.
R802.2 Design and construction. Roof-ceilings shall be designed and constructed in accordance with the provisions of this chapter and Figures R606.10(1), R606.10(2) and R606.10(3) or in accordance with AFPA/NDS and ASCE 7. Components of roof-ceilings shall be fastened in accordance with Table R602.3(1).

R802.3 Framing details.
Rafters shall be framed to ridge board or to each other with a gusset plate as a tie. Ridge board shall be at least 1-inch (25.4 mm) nominal thickness and not less in depth than the cut end of the rafter. At all valleys and hips there shall be a valley or hip rafter not less than 2-inch (51 mm) nominal thickness and not less in depth than the cut end of the rafter. Hip and valley rafters shall be supported at the ridge by a brace to a bearing partition or be designed to carry and distribute the specific load at that point. Where the roof pitch is less than three units vertical in 12 units horizontal (25-percent slope), structural members that support rafters and ceiling joists, such as ridge beams, hips and valleys, shall be designed as beams.

R802.3.1 Ceiling joist and rafter connections. Ceiling joists and rafters shall be nailed to each other in accordance with Tables R602.3(1) and R802.5.1(9), and the assembly shall be nailed to the top wall plate in accordance with Table R602.3(1). Ceiling joists shall be continuous or securely joined where they meet over interior partitions and nailed to adjacent rafters to provide a continuous tie across the building when such joists are parallel to the rafters.

Where ceiling joists are not parallel to rafters, subflooring or metal straps attached to the ends of the rafters shall be installed in a manner to provide a continuous tie across the building, or rafters shall be tied to 1-inch by 4-inch (25.4 mm by 102 mm) (nominal) minimum-size crossties. The connections shall be in accordance with Table R602.3(1) or connections of equivalent capacities shall be provided. Where ceiling joists or rafter ties are not provided at the top plate, the ridge formed by these rafters shall also be supported by a girder designed in accordance with accepted engineering practice.

Rafter ties shall be spaced not more than 4 feet (1219 mm) on center.
R802.3.2 Ceiling joists lapped. Ends of ceiling joists shall be lapped a minimum of 3 inches (76 mm) or butted over bearing partitions or beams and toenailed to the bearing member. When ceiling joists are used to provide resistance to rafter thrust, lapped joists shall be nailed together in accordance with Table R602.3(1) and butted joists shall be tied together in a manner to resist such thrust.
R802.4 Allowable ceiling joist spans. Spans for ceiling joists shall be in accordance with Tables R802.4(1) and R802.4(2). For other grades and species and for other loading conditions, refer to the AF&PA Span Tables for Joists and Rafters.

TABLE R802.4(1) CEILING JOIST SPANS FOR COMMON LUMBER SPECIES (Uninhabitable attics without storage, live load = 10 psf, L/D = 240)










(continued)


TABLE R802.4(1)—continued CEILING JOIST SPANS FOR COMMON LUMBER SPECIES (Uninhabitable attics without storage, live load = 10 psf, L/D = 240)






Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.
a. Span exceeds 26 feet in length.
b. North American spruce-pine-fir species only.



TABLE R802.4(2) CEILING JOIST SPANS FOR COMMON LUMBER SPECIES (Uninhabitable attics with limited storage, live load = 20 psf, L/D = 240)










(continued)


TABLE R802.4(2)—continued CEILING JOIST SPANS FOR COMMON LUMBER SPECIES (Uninhabitable attics with limited storage, live load = 20 psf, L/D = 240)







R802.4.1 Attics without storage. In conventional rafter construction, the unsupported span of ceiling joists shall not exceed the values set forth in Table R802.4(1) in attics which do not have a clear height of 42 inches (1067 mm) or more between joist and rafter, provided the design live load does not exceed 10 psf (479 Pa) and the design dead load does not exceed 5 psf (239Pa).
R802.4.2 Attics with storage. In conventional rafter construction, the unsupported span of ceiling joists shall not exceed the values set forth in Table R802.4(2) in attics which are not served by a fixed stair, have a clear height of 42 inches (1067 mm) or more between joist and rafter, and have a design live load not exceeding 20 psf (958 Pa) and a design dead load not exceeding 10 psf (479 Pa). The maximum allowable span of joists that support attic spaces that are accessed by means of a fixed stair shall be determined in accordance with Table R502.3.1(1) for residential sleeping areas.
R802.5 Allowable rafter spans. Spans for rafters shall be in accordance with Tables R802.5.1(1) through R802.5.1(8). For other grades and species and for other loading conditions, refer to the AF&PA Span Tables for Joists and Rafters and applicable provisions of ASCE 7. The span of each rafter shall be measured along the horizontal projection of the rafter.

R802.5.1 Purlins. Purlins are permitted to be installed to reduce the span of rafters as shown in Figure R802.5.1. Purlins shall be sized no less than the required size of the rafters that they support. Purlins shall be continuous and shall be supported by 2-inch by 4-inch (51 mm by 102 mm) braces installed to bearing walls at a slope not less than 45 degrees from the horizontal. The braces shall be spaced not more than 4 feet (1219 mm) on center and the unbraced length of braces shall not exceed 8 feet (2438 mm).

TABLE R802.5.1(1) RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof live load=20 psf, ceiling not attached to rafters, L/D = 180)










(continued)


TABLE R802.5.1(1)—continued RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof live load=20 psf, ceiling not attached to rafters, L/D = 180)






Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on
the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
 

HC/HR
Rafter Span Adjustment Factor
2/3 or greater
0.50
1/2
0.58
1/3
0.67
1/4
0.76
1/5
0.83
1/6
0.90
1/7.5 and less
1.00
where: H C = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
          H R = Height of roof ridge measured vertically above the top of the rafter support walls.
b. Span exceeds 26 feet in length.
c. North American spruce-pine-fir species only.



TABLE R802.5.1(2) RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof live load=20 psf, ceiling attached to rafters, L/D = 240)











(continued)


TABLE R802.5.1(2)—continued RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof live load=20 psf, ceiling attached to rafters, L/D = 240)







Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
 

HC/HR
Rafter Span Adjustment Factor
2/3 or greater
0.50
1/2
0.58
1/3
0.67
1/4
0.76
1/5
0.83
1/6
0.90
1/7.5 and less
1.00
where: H C = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
 H R = Height of roof ridge measured vertically above the top of the rafter support walls.
b. Span exceeds 26 feet in length.
c. North American spruce-pine-fir species only.



TABLE R802.5.1(3) RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=30 psf, ceiling not attached to rafters, L/D = 180)






(continued)


TABLE R802.5.1(3)—continued RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=30 psf, ceiling not attached to rafters, L/D = 180)










Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
 

HC/HR
Rafter Span Adjustment Factor
2/3 or greater
0.50
1/2
0.58
1/3
0.67
1/4
0.76
1/5
0.83
1/6
0.90
1/7.5 and less
1.00
where: H C = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
 H R = Height of roof ridge measured vertically above the top of the rafter support walls.
b. Span exceeds 26 feet in length.
c. North American spruce-pine-fir species only.



TABLE R802.5.1(4) RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=50 psf or less, ceiling not attached to rafters, L/D = 180)






(continued)


TABLE R802.5.1(4)—continued RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=50 psf or less, ceiling not attached to rafters, L/D = 180)






TABLE R802.5.1(5) RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=30 psf, ceiling attached to rafters, L/D = 240)






(continued)


TABLE R802.5.1(5)—continued RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=30 psf, ceiling attached to rafters, L/D = 240)






Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:

HC/HR
Rafter Span Adjustment Factor
2/3 or greater
0.50
1/2
0.58
1/3
0.67
1/4
0.76
1/5
0.83
1/6
0.90
1/7.5 and less
1.00

where: H C = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
 H R = Height of roof ridge measured vertically above the top of the rafter support walls.
b. Span exceeds 26 feet in length.
c. North American spruce-pine-fir species only.



TABLE R802.5.1(6) RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=50 psf or less, ceiling attached to rafters, L/D = 240)










(continued)


TABLE R802.5.1(6)—continued RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=50 psf or less, ceiling attached to rafters, L/D = 240)






Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:

HC/HR
Rafter Span Adjustment Factor
2/3 or greater
0.50
1/2
0.58
1/3
0.67
1/4
0.76
1/5
0.83
1/6
0.90
1/7.5 and less
1.00

where: H C = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
 H R = Height of roof ridge measured vertically above the top of the rafter support walls.
b. North American spruce-pine-fir species only.



TABLE R802.5.1(7) RAFTER SPANS COMMON LUMBER SPECIES (Ground snow load=70 psf or less, ceiling not attached to rafters, L/D = 180)










(continued)


TABLE R802.5.1(7)—continued RAFTER SPANS COMMON LUMBER SPECIES (Ground snow load=70 psf or less, ceiling not attached to rafters, L/D = 180)










Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:


HC/HR
Rafter Span Adjustment Factor
2/3 or greater
0.50
1/2
0.58
1/3
0.67
1/4
0.76
1/5
0.83
1/6
0.90
1/7.5 and less
1.00
where: H C = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
 H R = Height of roof ridge measured vertically above the top of the rafter support walls.
b. North American spruce-pine-fir species only.



TABLE R802.5.1(8) RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground Snow Load = 70 psf or less, ceiling attached to rafters, L/D=240)










(continued)


TABLE R802.5.1(8)—continued RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground Snow Load = 70 psf or less, ceiling attached to rafters, L/D=240)






Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:

HC/HR
Rafter Span Adjustment Factor
2/3 or greater
0.50
1/2
0.58
1/3
0.67
1/4
0.76
1/5
0.83
1/6
0.90
1/7.5 and less
1.00

where: H C = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
 H R = Height of roof ridge measured vertically above the top of the rafter support walls.
b. North American spruce-pine-fir species only.



TABLE R802.5.1(9) RAFTER/CEILING JOIST HEEL JOINT CONNECTIONSa,b,c,d,e,f


RAFTER SLOPE
RAFTER SPACING
(inches)

GROUND SNOW LOAD (psf)
30
50
70
Roof span (feet)
12
20
28
36
12
20
28
36
12
20
28
36
Required number of 16d common nailsa,bper heel joint splicesc,d,e,f
3:12
12
16
24
4
5
7
6
8
11
8
11
16
11
14
21
5
6
9
8
11
16
12
15
23
15
20
30
6
8
12
11
14
21
15
20
30
20
26
39
4:12
12
16
24
3
4
5
5
6
9
6
8
12
8
11
16
4
5
7
6
8
12
9
12
17
11
15
22
5
6
9
8
11
16
12
15
23
15
20
29
5:12
12
16
24
3
3
4
4
5
7
5
7
10
7
9
13
3
4
6
5
7
10
7
9
14
9
12
18
4
5
7
7
9
13
9
12
18
12
16
23
7:12
12
16
24
3
3
3
3
4
5
4
5
7
5
6
9
3
3
4
4
5
7
5
7
10
7
9
13
3
4
5
5
6
9
7
9
13
9
11
17
9:12
12
16
24
3
3
3
3
3
4
3
4
6
4
5
7
3
3
3
3
4
6
4
5
8
5
7
10
3
3
4
4
5
7
5
7
10
7
9
13
12:12
12
16
24
3
3
3
3
3
3
3
3
4
3
4
6
3
3
3
3
3
4
3
4
6
4
5
8
3
3
3
3
4
6
4
5
8
5
7
10


For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.
a. 40d box nails shall be permitted to be substituted for 16d common nails.
b Nailing requirements shall be permitted to be reduced 25 percent if nails are clinched.
c. Heel joint connections are not required when the ridge is supported by a load-bearing wall, header or ridge beam.
d. When intermediate support of the rafter is provided by vertical struts or purlins to a loadbearing wall, the tabulated
heel joint connection requirements shall be permitted to be reduced proportionally to the reduction in span.
e. Equivalent nailing patterns are required for ceiling joist to ceiling joist lap splices.
f. When rafter ties are substituted for ceiling joists, the heel joint connection requirement shall be taken as the
tabulated heel joint connection requirement for two-thirds of the actual rafter-slope.







For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.018 rad.
NOTE:
Where ceiling joints run perpendicular to the rafters, rafter ties shall be nailed to the rafter near the plate line and spaced not more than 4 feet on center.



FIGURE R802.5.1 BRACED RAFTER CONSTRUCTION
R802.6 Bearing. The ends of each rafter or ceiling joist shall have not less than 11/2 inches (38 mm) of bearing on wood or metal and not less than 3 inches (76 mm) on masonry or concrete.

R802.6.1 Finished ceiling material. If the finished ceiling material is installed on the ceiling prior to the attachment of the ceiling to the walls, such as in construction at a factory, a compression strip of the same thickness as the finish ceiling material shall be installed directly above the top plate of bearing walls if the compressive strength of the finish ceiling material is less than the loads it will be required to withstand. The compression strip shall cover the entire length of such top plate and shall be at least one-half the width of the top plate. It shall be of material capable of transmitting the loads transferred through it.
R802.7 Cutting and notching. Structural roof members shall not be cut, bored or notched in excess of the limitations specified in this section.

R802.7.1 Sawn lumber. Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span. Notches at the ends of the member shall not exceed one-fourth the depth of the member. The tension side of members 4 inches (102 mm) or greater in nominal thickness shall not be notched except at the ends of the members. The diameter of the holes bored or cut into members shall not exceed one-third the depth of the member. Holes shall not be closer than 2 inches (51 mm) to the top or bottom of the member, or to any other hole located in the member. Where the member is also notched, the hole shall not be closer than 2 inches (51 mm) to the notch.

Exception:
Notches on cantilevered portions of rafters are permitted provided the dimension of the remaining portion of the rafter is not less than 4-inch nominal (102 mm) and the length of the cantilever does not exceed 24 inches (610 mm).
R802.7.2 Engineered wood products. Cuts, notches and holes bored in laminated veneer lumber, glue-laminated members or I-joists are not permitted unless the effect of such penetrations are specifically considered in the design of the member.
R802.8 Lateral support. Rafters and ceiling joists having a depth-to-thickness ratio exceeding 5 to 1 based on nominal dimensions shall be provided with lateral support at points of bearing to prevent rotation.

R802.8.1 Bridging. Rafters and ceiling joists having a depth-to-thickness ratio exceeding 6 to 1 based on nominal dimensions shall be supported laterally by solid blocking, diagonal bridging (wood or metal) or a continuous 1-inch by 3-inch (25.4 mm by 76 mm) wood strip nailed across the rafters or ceiling joists at intervals not exceeding 8 feet (2438 mm).
R802.9 Framing of openings. Openings in roof and ceiling framing shall be framed with header and trimmer joists. When the header joist span does not exceed 4 feet (1219 mm), the header joist may be a single member the same size as the ceiling joist or rafter. Single trimmer joists may be used to carry a single header joist that is located within 3 feet (914 mm) of the trimmer joist bearing. When the header joist span exceeds 4 feet (1219 mm), the trimmer joists and the header joist shall be doubled and of sufficient cross section to support the ceiling joists or rafter framing into the header. Approved hangers shall be used for the header joist to trimmer joist connections when the header joist span exceeds 6 feet (1829 mm). Tail joists over 12 feet (3658 mm) long shall be supported at the header by framing anchors or on ledger strips not less than 2 inches by 2 inches (51 mm by 51 mm).

R802.10 Wood trusses.


R802.10.1 Truss design drawings. Truss design drawings, prepared in conformance with Section R802.10.1, shall be provided to the code enforcement official and approved prior to installation. Truss design drawings shall include, at a minimum, the information specified below. Truss design drawing shall be provided with the shipment of trusses delivered to the jobsite.
1.    Slope or depth, span and spacing.
2.    Location of all joints.
3.    Required bearing widths.
4.    Design loads as applicable.
4.1.    Top chord live load (including snow loads).
4.2.    Top chord dead load.
4.3.    Bottom chord live load.
4.4.    Bottom chord dead load.
4.5.    Concentrated loads and their points of application.
4.6.    Controlling wind and earthquake loads.
5.    Adjustments to lumber and joint connector design values for conditions of use.
6.    Each reaction force and direction.
7.    Joint connector type and description (e.g., size, thickness or gauge) and the dimensioned location of each joint connector except where symmetrically located relative to the joint interface.
8.    Lumber size, species and grade for each member.
9.    Connection requirements for:
9.1.    Truss to truss girder.
9.2.    Truss ply to ply.
9.3.    Field splices.
10.    Calculated deflection ratio and/or maximum description for live and total load.
11.    Maximum axial compression forces in the truss members to enable the building designer to design the size, connections and anchorage of the permanent continuous lateral bracing. Forces shall be shown on the truss design drawing or on supplemental documents.
12.    Required permanent truss member bracing location.
R802.10.2 Design. Wood trusses shall be designed in accordance with accepted engineering practice. The design and manufacture of metal plate connected wood trusses shall comply with ANSI/TPI 1. The truss design drawings shall be prepared by a registered professional where required by the statutes of the jurisdiction in which the project is to be constructed in accordance with Section R106.1.
R802.10.3 Bracing. Trusses shall be braced to prevent rotation and provide lateral stability in accordance with the requirements specified in the construction documents for the building and on the individual truss design drawings. In the absence of specific bracing requirements, trusses shall be braced in accordance with TPI/HIB.
R802.10.4 Alterations to trusses. Truss members shall not be cut, notched, drilled, spliced or otherwise altered in any way without the approval of a registered design professional. Alterations resulting in the addition of load (e.g., HVAC equipment, water heater) that exceeds the design load for the truss shall not be permitted without verification that the truss is capable of supporting such additional loading.
R802.10.5 Truss to wall connection. Provide minimum required uplift force connectors as specified by the roof truss design drawings for the roof truss to wall connection. Connectors shall be installed in accordance with the manufacturer’s specifications.
R802.10.6 Truss live loads for attics with limited storage. Where there are two or more adjacent trusses with the same web configuration, the bottom chords of the trusses shall be designed to support a minimum live load of 20 psf (958 Pa) in attics which are not served by a fixed stair. The design live load shall be applied to portions of the bottom chord that are capable of containing a rectangle 42 inches (1067 mm) high by 2 feet (610 mm) wide, or greater, located within the plane of the truss. The rectangle shall fit between the top of the bottom chord and the bottom of any other truss member, provided that each of the following criteria is met:
1.    The attic area is accessible by a pull-down stairway or framed opening in accordance with Section R807.1; and
2.    The truss shall have a bottom chord pitch less than 2:12.

The bottom chords of trusses in attic spaces served by a fixed stair shall be designed to support the minimum live load as for sleeping rooms, in accordance with Table R301.5.
R802.10.7 Truss live loads for attics without storage. Bottom chords of trusses not meeting the criteria for attics with storage per Section R802.10.6 shall be designed for a minimum live load of 10 psf (479 Pa) uniformly distributed over the entire span. This live load shall not be required to be applied concurrently with other live loads.
R802.11 Roof tie-down.

TABLE R802.11 REQUIRED STRENGTH OF TRUSS OR RAFTER CONNECTIONS TO RESIST WIND UPLIFT FORCESa,b,c,e,f (Pounds per connection)


BASIC WIND SPEED
(3–second gust)

ROOF SPAN (feet)
OVERHANGSd (pounds/feet)
12
20
24
28
32
36
40
85
-72
-120
-145
-169
-193
-217
-241
-38.55
90
-91
-151
-181
-212
-242
-272
-302
-43.22
100
-131
-218
-262
-305
-349
-393
-436
-53.36
110
-175
-292
-351
-409
-467
-526
-584
-64.56


For SI: 1 inch = 25.4 mm, 1 foot = 305 mm, 1 mph = 1.61 km/hr, 1 pound/foot = 14.5939 N/m, 1 pound = 0.454 kg.
a. The uplift connection requirements are based on a 30 foot mean roof height located in Exposure B. For Exposures C and D and for other mean roof heights, multiply the above loads by the Adjustment Coefficients in Table R-301.2(3).
b. The uplift connection requirements are based on the framing being spaced 24 inches on center. Multiply by 0.67 for framing spaced 16 inches on center and multiply by 0.5 for framing spaced 12 inches on center.
c. The uplift connection requirements include an allowance for 10 pounds of dead load.
d. The uplift connection requirements do not account for the effects of overhangs. The magnitude of the above loads shall be increased by adding the overhang loads found in the table. The overhang loads are also based on framing spaced 24 inches on center. The overhang loads given shall be multiplied by the overhang projection and added to the roof uplift value in the table.
e. The uplift connection requirements are based upon wind loading on end zones as defined in Section M1609.6 of the Building Code of New York State. Connection loads for connections located a distance of 20% of the least horizontal dimension of the building from the corner of the building are permitted to
be reduced by multiplying the table connection value by 0.7 and multiplying the overhang load by 0.8.
f. For wall-to-wall and wall-to-foundation connections, the capacity of the uplift connector is permitted to be reduced by 100 pounds for each full wall
above. (For example, if a 600-pound rated connector is used on the roof framing, a 500-pound rated connector is permitted at the next floor level down.)



R802.11.1 Uplift resistance. Roof assemblies which are subject to wind uplift pressures of 20 pounds per square foot (0.958 kN/m2) or greater shall have roof rafters or trusses attached to their supporting wall assemblies by connections capable of providing the resistance required in Table R802.11. Wind uplift pressures shall be determined using an effective wind area of 100 square feet (9.3 m2) and Zone 1 in Table R301.2(2), as adjusted for height and exposure per Table R301.2(3). For roof trusses, where differences occur between the uplift value specified by Table R802.11 and the uplift value specified by the truss manufacturer, the uplift value of the truss manufacturer shall apply.

A continuous load path shall be provided to transmit the uplift forces from the rafter or truss ties to the foundation.