• CHAPTER8
    ROOF-CEILING CONSTRUCTION 

    User note:

    About this chapter: Chapter 8 addresses the design and construction of roof-ceiling systems. This chapter contains two roof-ceiling framing systems: wood framing and cold-formed steel framing. Allowable span tables are provided to simplify the selection of rafter and ceiling joist size for wood roof framing and cold-formed steel framing. Chapter 8 also provides requirements for the application of ceiling finishes, the proper ventilation of concealed spaces in roofs (for example, enclosed attics and rafter spaces), unvented attic assemblies and attic access.

    SECTIONR801
    GENERAL

    R801.1Application.

    The provisions of this chapter shall control the design and construction of the roof-ceiling system for buildings.

    R801.2Requirements.

    Roof and ceiling construction shall be capable of accommodating all loads imposed in accordance with Section R301 and of transmitting the resulting loads to the supporting structural elements.

    R801.3Roof drainage.

    In areas where expansive soils or collapsible soils are known to exist, all dwellings shall have a controlled method of water disposal from roofs that will collect and discharge roof drainage to the ground surface not less than 5 feet (1524 mm) from foundation walls or to an approved drainage system.

    SECTIONR802
    WOOD ROOF FRAMING 

    R802.1General.

    Wood and wood-based products used for load-supporting purposes shall conform to the applicable provisions of this section.

    R802.1.1Sawn lumber.

    Sawn lumber shall be identified by a grade mark of an accredited lumber grading or inspection agency and have design values certified 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.

    R802.1.1.1End-jointed lumber.

    Approved end-jointed lumber identified by a grade mark conforming to Section R802.1.1 shall be permitted to be used interchangeably with solid-sawn members of the same species and grade. End-jointed lumber used in an assembly required elsewhere in this code to have a fire-resistance rating shall have the designation “Heat-Resistant Adhesive” or “HRA” included in its grade mark.

    R802.1.2Structural glued-laminated timbers.

    Glued-laminated timbers shall be manufactured and identified as required in ANSI A190.1, ANSI 117 and ASTM D3737.

    R802.1.3Structural log members.

    Structural log members shall comply with the provisions of ICC 400.

    R802.1.4Structural composite lumber.

    Structural capacities for structural composite lumber shall be established and monitored in accordance with ASTM D5456.

    R802.1.5Fire-retardant-treated wood.

    Fire-retardant-treated wood (FRTW) is any wood product that, when impregnated with chemicals by a pressure process or other means during manufacture, shall have, when tested in accordance with ASTM E84 or UL 723, a listed flame spread index of 25 or less and does not show evidence of significant progressive combustion where 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.

    R802.1.5.1Pressure process.

    For wood products impregnated with chemicals by a pressure process, the process shall be performed in closed vessels under pressures not less than 50 pounds per square inch gauge (psig) (344.7 kPa).

    R802.1.5.2Other means during manufacture.

    For wood products produced by other means during manufacture the treatment shall be an integral part of the manufacturing process of the wood product. The treatment shall provide permanent protection to all surfaces of the wood product.

    R802.1.5.3Testing.

    For wood products produced by other means during manufacture, other than a pressure process, all sides of the wood product shall be tested in accordance with and produce the results required in Section R802.1.5. Testing of only the front and back faces of wood structural panels shall be permitted.

    R802.1.5.4Labeling.

    In addition to the labels required by Section 802.1.1 for sawn lumber and Section 803.2.1 for wood structural panels, each piece of fire-retardant-treated lumber and wood structural panel shall be labeled. The label shall contain:

    1. 1.The identification mark of an approved agency in accordance with Section 1703.5 of the International Building Code.

    2. 2.Identification of the treating manufacturer.

    3. 3.The name of the fire-retardant treatment.

    4. 4.The species of wood treated.

    5. 5.Flame spread index and smoke-developed index.

    6. 6.Method of drying after treatment.

    7. 7.Conformance to applicable standards in accordance with Sections R802.1.5.5 through R802.1.5.10.

    8. 8.For FRTW exposed to weather, or a damp or wet location, the words “No increase in the listed classification when subjected to the Standard Rain Test” (ASTM D2898).

    R802.1.5.5Strength 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 on an approved method of investigation that 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.

    R802.1.5.6Wood 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 D5516. The test data developed by ASTM D5516 shall be used to develop adjustment factors, maximum loads and spans, or both for untreated plywood design values in accordance with ASTM D6305. Each manufacturer shall publish the allowable maximum loads and spans for service as floor and roof sheathing for their treatment.

    R802.1.5.7Lumber.

    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 D5664. The test data developed by ASTM D5664 shall be used to develop modification factors for use at or near room temperature and at elevated temperatures and humidity in accordance with ASTM D6841. Each manufacturer shall publish the modification factors for service at temperatures of not less than 80°F (27°C) and for roof framing. The roof framing modification factors shall take into consideration the climatological location.

    R802.1.5.8Exposure 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 not an increase in the listed flame spread index as defined in Section R802.1.5 when subjected to ASTM D2898.

    R802.1.5.9Interior applications.

    Interior fire-retardant-treated wood shall have a moisture content of not over 28 percent when tested in accordance with ASTM D3201 procedures at 92-percent relative humidity. Interior fire-retardant-treated wood shall be tested in accordance with Section R802.1.5.6 or R802.1.5.7. Interior fire-retardant-treated wood designated as Type A shall be tested in accordance with the provisions of this section.

    R802.1.5.10Moisture 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 R802.1.5.6 for plywood and R802.1.5.7 for lumber.

    R802.1.6Cross-laminated timber.

    Cross-laminated timber shall be manufactured and identified as required by ANSI/APA PRG 320.

    R802.1.7Engineered wood rim board.

    Engineered wood rim boards shall conform to ANSI/APA PRR 410 or shall be evaluated in accordance with ASTM D7672. Structural capacities shall be in accordance with ANSI/APA PRR 410 or established in accordance with ASTM D7672. Rim boards conforming to ANSI/APA PRR 410 shall be marked in accordance with that standard.

    R802.1.8Prefabricated wood I-joists.

    Structural capacities and design provisions for prefabricated wood I-joists shall be established and monitored in accordance with ASTM D5055.

    R802.2Design and construction.

    The roof and ceiling assembly shall provide continuous ties across the structure to prevent roof thrust from being applied to the supporting walls. The assembly shall be designed and constructed in accordance with the provisions of this chapter and Figures R606.11(1), R606.11(2) and R606.11(3) or in accordance with AWC NDS.

    R802.3Ridge.

    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 joist or rafter ties do not provide continuous ties across the structure, a ridge beam shall be provided and supported on each end by a wall or girder.

    R802.4Rafters.

    Rafters shall be in accordance with this section.

    R802.4.1Rafter 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.

    TABLE R802.4.1(1)

    RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof live load = 20 psf, ceiling not attached to rafters, L/Δ = 180)

    RAFTER SPACING (inches)SPECIES AND GRADEDEAD LOAD = 10 psfDEAD LOAD = 20 psf
    2 × 42 × 62 × 82 × 102 × 122 × 42 × 62 × 82 × 102 × 12
    Maximum rafter spansa
    (feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)
    12Douglas fir-larchSS11-618-023-9Note bNote b11-618-023-9Note bNote b
    Douglas fir-larch#111-117-422-5Note bNote b10-615-419-523-9Note b
    Douglas fir-larch#210-1016-1021-426-0Note b10-014-718-522-626-0
    Douglas fir-larch#38-912-1016-319-1023-07-711-114-117-219-11
    Hem-firSS10-1017-022-5Note bNote b10-1017-022-5Note bNote b
    Hem-fir#110 -716-822-0Note bNote b10-415-219-223-5Note b
    Hem-fir#210-115-1120-825-3Note b9-814-217-1121-1125-5
    Hem-fir#38-712-615-1019-522-67-510-1013-916-919-6
    Southern pineSS11-317-823-4Note bNote b11-317-823-4Note bNote b
    Southern pine#110-1017-022-5Note bNote b10-615-819-1023-2Note b
    Southern pine#210-415-719-823-5Note b9-013-617-120-323-10
    Southern pine#38-011-914-1018-021-46-1110-212-1015-718-6
    Spruce-pine-firSS10-716-821-11Note bNote b10-716-821-9Note bNote b
    Spruce-pine-fir#110-416-321-025-8Note b9-1014-418-222-325-9
    Spruce-pine-fir#210-416-321-025-8Note b9-1014-418-222-325-9
    Spruce-pine-fir#38-712-615-1019-522-67-510-1013-916-919-6
    16Douglas fir-larchSS10-516-421-7Note bNote b10-516-320-725-2Note b
    Douglas fir-larch#110-015-419-523-9Note b9-113-316-1020-723-10
    Douglas fir-larch#29-1014-718-522-626-08-712-716-019-622-7
    Douglas fir-larch#37-711-114-117-219-116-79-812-1214-1117-3
    Hem-firSS9-1015-620-5Note bNote b9-1015-619-1124-4Note b
    Hem-fir#19-815-219-223-5Note b9-013-116-720-423-7
    Hem-fir#29-214-217-1121-1125-58-512-315-618-1122-0
    Hem-fir#37-510-1013-916-919-66-59-511-1114-616-10
    Southern pineSS10-316-121-2Note bNote b10-316-121-225-7Note b
    Southern pine#19-1015-619-1023-2Note b9-113-717-220-123-10
    Southern pine#29-013-617-120-323-107-911-814-917-620-8
    Southern pine#36-1110-212-1015-718-66-08-1011-213-616-0
    Spruce-pine-firSS9-815-219-1125-5Note b9-814-1018-1023-0Note b
    Spruce-pine-fir#19-514-418-222-325-98-612-515-919-322-4
    Spruce-pine-fir#29-514-418-222-325-98-612-515-919-322-4
    Spruce-pine-fir#37-510-1013-916-919-66-59-511-1114-616-10
    19.2Douglas fir-larchSS9-1015-520-425-11Note b9-1014-1018-1023-0Note b
    Douglas fir-larch#19-514-017-921-825-28-412-215-418-921-9
    Douglas fir-larch#29-113-316-1020-723-107-1011-614-717-1020-8
    Douglas fir-larch#36-1110-212-1015-818-36-08-911-212-715-9
    Hem-firSS9-314-719-224-6Note b9-314-418-222-325-9
    Hem-fir#19-113-1017-621-524-108-212-015-218-621-6
    Hem-fir#28-812-1116-420-023-27-811-214-217-420-1
    Hem-fir#36-99-1112-715-417-95-108-710-1013-315-5
    Southern pineSS9-815-219-1125-5Note b9-815-219-723-4Note b
    Southern pine#19-314-318-121-225-28-412-415-818-421-9
    Southern pine#28-212-315-718-621-97-110-813-616-018-10
    Southern pine#36-49-411-914-316-105-68-110-212-414-7
    Spruce-pine-firSS9-114-318-923-11Note b9-113-717-221-024-4
    Spruce-pine-fir#18-1013-116-720-323-67-911-414-417-720-4
    Spruce-pine-fir#28-1013-116-720-323-67-911-414-417-720-4
    Spruce-pine-fir#36-99-1112-715-417-95-108-710-1013-315-5
    24Douglas fir-larchSS9-114-418-1023-9Note b9-113-316-1020-723-10
    Douglas fir-larch#18-712-615-1019-522-67-510-1013-916-919-6
    Douglas fir-larch#28-211-1115-118-521-47-010-413-015-1118-6
    Douglas fir-larch#36-29-111-614-116-35-47-1010-012-214-1
    Hem-firSS8-713-617-1022-9Note b8-712-1016-319-1023-0
    Hem-fir#18-512-415-819-222-27-410-913-716-719-3
    Hem-fir#27-1111-714-817-1020-96-1010-012-815-617-11
    Hem-fir#36-18-1011-313-815-115-37-89-911-1013-9
    Southern pineSS8-1114-118-623-8Note b8-1113-1017-620-1024-8
    Southern pine#18-712-916-218-1122-67-511-114-016-519-6
    Southern pine#27-411-013-1116-619-66-49-612-114-416-10
    Southern pine#35-88-410-612-915-14-117-39-111-013-1
    Spruce-pine-firSS8-513-317-521-825-28-412-215-418-921-9
    Spruce-pine-fir#18-011-914-1018-221-06-1110-212-1015-818-3
    Spruce-pine-fir#28-011-914-1018-221-06-1110-212-1015-818-3
    Spruce-pine-fir#36-18-1011-313-815-115-37-89-911-1013-9

    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 kPa.

    1. 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. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:

      HC/HRRafter Span Adjustment Factor
      1/30.67
      1/40.76
      1/50.83
      1/60.90
      1/7.5 or less1.00

      where:

      HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

      HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    2. b.Span exceeds 26 feet in length.

    TABLE R802.4.1(2)

    RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof live load = 20 psf, ceiling attached to rafters, L/Δ = 240)

    RAFTER SPACING (inches)SPECIES AND GRADEDEAD LOAD = 10 psfDEAD LOAD = 20 psf
    2 × 42 × 62 × 82 × 102 × 122 × 42 × 62 × 82 × 102 × 12
    Maximum rafter spansa
    (feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)
    12Douglas fir-larchSS10-516-421-7Note bNote b10-516-421-7Note bNote b
    Douglas fir-larch#110-015-920-10Note bNote b10-015-419-523-9Note b
    Douglas fir-larch#29-1015-620-526-0Note b9-1014-718-522-626-0
    Douglas fir-larch#38-912-1016-319-1023-07-711-114-117-219-11
    Hem-firSS9-1015-620-5Note bNote b9-1015-620-5Note bNote b
    Hem-fir#19-815-219-1125-5Note b9-815-219-223-5Note b
    Hem-fir#29-214-519-024-3Note b9-214-217-1121-1125-5
    Hem-fir#38-712-615-1019-522-67-510-1013-916-919-6
    Southern pineSS10-316-121-2Note bNote b10-316-121-2Note bNote b
    Southern pine#19-1015-620-5Note bNote b9-1015-619-1023-2Note b
    Southern pine#29-514-919-623-5Note b9-013-617-120-323-10
    Southern pine#38-011-914-1018-021-46-1110-212-1015-718-6
    Spruce-pine-firSS9-815-219-1125-5Note b9-815-219-1125-5Note b
    Spruce-pine-fir#19-514-919-624-10Note b9-514-418-222-325-9
    Spruce-pine-fir#29-514-919-624-10Note b9-514-418-222-325-9
    Spruce-pine-fir#38-712-615-1019-522-67-510-1013-916-919-6
    16Douglas fir-larchSS9-614-1119-725-0Note b9-614-1119-725-0Note b
    Douglas fir-larch#19-114-418-1123-9Note b9-113-316-1020-723-10
    Douglas fir-larch#28-1114-118-522-626-08-712-716-019-622-7
    Douglas fir-larch#37-711-114-117-219-116-79-812-214-1117-3
    Hem-firSS8-1114-118-623-8Note b8-1114-118-623-8Note b
    Hem-fir#18-913-918-123-1Note b8-913-116-720-423-7
    Hem-fir#28-413-117-321-1125-58-412-315-618-1122-0
    Hem-fir#37-510-1013-916-919-66-59-511-1114-616-10
    Southern pineSS9-414-719-324-7Note b9-414-719-324-7Note b
    Southern pine#18-1114-118-623-2Note b8-1113-717-220-123-10
    Southern pine#28-713-517-120-323-107-911-814-917-620-8
    Southern pine#36-1110-212-1015-718-66-08-1011-213-616-0
    Spruce-pine-firSS8-913-918-123-1Note b8-913-918-123-0Note b
    Spruce-pine-fir#18-713-517-922-325-98-612-515-919-322-4
    Spruce-pine-fir#28-713-517-922-325-98-612-515-919-322-4
    Spruce-pine-fir#37-510-1013-916-919-66-59-511-1114-616-10
    19.2Douglas fir-larchSS8-1114-018-523-7Note b8-1114-018-523-0Note b
    Douglas fir-larch#18-713-617-921-825-28-412-215-418-921-9
    Douglas fir-larch#28-513-316-1020-723-107-1011-614-717-1020-8
    Douglas fir-larch#36-1110-212-1015-818-36-08-911-213-715-9
    Hem-firSS8-513-317-522-3Note b8-513-317-522-325-9
    Hem-fir#18-312-1117-121-524-108-212-015-218-621-6
    Hem-fir#27-1012-416-320-023-27-811-214-217-420-1
    Hem-fir#36-99-1112-715-417-95-108-710-1013-315-5
    Southern pineSS8-913-918-223-1Note b8-913-918-223-1Note b
    Southern pine#18-513-317-521-225-28-412-415-818-421-9
    Southern pine#28-112-315-718-621-97-110-813-616-018-10
    Southern pine#36-49-411-914-316-105-68-110-212-414-7
    Spruce-pine-firSS8-312-1117-121-9Note b8-312-1117-121-024-4
    Spruce-pine-fir#18-112-816-720-323-67-911-414-417-720-4
    Spruce-pine-fir#28-112-816-720-323-67-911-414-417-720-4
    Spruce-pine-fir#36-99-1112-715-417-95-108-710-1013-315-5
    24Douglas fir-larchSS8-313-017-221-10Note b8-313-016-1020-723-10
    Douglas fir-larch#18-012-615-1019-522-67-510-1013-916-919-6
    Douglas fir-larch#27-1011-1115-118-521-47-010-413-015-1118-6
    Douglas fir-larch#36-29-111-614-116-35-47-1010-012-214-1
    Hem-firSS7-1012-316-220-825-17-1012-316-219-1023-0
    Hem-fir#17-812-015-819-222-27-410-913-716-719-3
    Hem-fir#27-311-514-817-1020-96-1010-012-815-617-11
    Hem-fir#36-18-1011-313-815-115-37-89-911-1013-9
    Southern pineSS8-112-916-1021-6Note b8-112-916-1020-1024-8
    Southern pine#17-1012-316-218-1122-67-511-114-016-519-6
    Southern pine#27-411-013-1116-619-66-49-612-114-416-10
    Southern pine#35-88-410-612-915-14-117-39-111-013-1
    Spruce-pine-firSS7-812-015-1020-224-77-812-015-418-921-9
    Spruce-pine-fir#17-611-914-1018-221-06-1110-212-1015-818-3
    Spruce-pine-fir#27-611-914-1018-221-06-1110-212-1015-818-3
    Spruce-pine-fir#36-18-1011-313-815-115-37-89-911-1013-9

    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 kPa.

    1. 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. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:

      HC/HRRafter Span Adjustment Factor
      1/30.67
      1/40.76
      1/50.83
      1/60.90
      1/7.5 or less1.00

      where:

      HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

      HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    2. b.Span exceeds 26 feet in length.

    TABLE R802.4.1(3)

    RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load = 30 psf, ceiling not attached to rafters, L/Δ = 180)

    RAFTER SPACING (inches)SPECIES AND GRADEDEAD LOAD = 10 psfDEAD LOAD = 20 psf
    2 × 42 × 62 × 82 × 102 × 122 × 42 × 62 × 82 × 102 × 12
    Maximum rafter spansa
    (feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)
    12Douglas fir-larchSS10-015-920-9Note bNote b10-015-920-524-11Note b
    Douglas fir-larch#19-814-918-822-9Note b9-013-216-820-423-7
    Douglas fir-larch#29-614-017-821-725-18-612-615-1019-422-5
    Douglas fir-larch#37-310-813-616-619-26-69-612-114-917-1
    Hem-firSS9-614-1019-725-0Note b9-614-1019-724-1Note b
    Hem-fir#19-314-618-522-626-08-1113-016-620-123-4
    Hem-fir#28-1013-717-221-024-48-412-215-418-921-9
    Hem-fir#37-110-513-216-118-86-49-411-914-516-8
    Southern pineSS9-1015-620-5Note bNote b9-1015-620-525-4Note b
    Southern pine#19-614-1019-022-3Note b9-013-517-019-1123-7
    Southern pine#28-712-1116-419-522-107-811-714-817-420-5
    Southern pine#36-79-912-415-017-95-118-911-013-515-10
    Spruce-pine-firSS9-314-719-224-6Note b9-314-718-822-9Note b
    Spruce-pine-fir#19-113-917-521-424-88-512-415-719-122-1
    Spruce-pine-fir#29-113-917-521-424-88-512-415-719-122-1
    Spruce-pine-fir#37-110-513-216-118-86-49-411-914-516-8
    16Douglas fir-larchSS9-114-418-1024-1Note b9-114-017-821-725-1
    Douglas fir-larch#18-912-916-219-922-107-1011-514-517-820-5
    Douglas fir-larch#28-312-115-418-921-87-510-1013-816-919-5
    Douglas fir-larch#36-49-311-814-316-75-88-310-612-914-10
    Hem-firSS8-713-617-1022-9Note b8-713-617-120-1024-2
    Hem-fir#18-512-715-1119-622-77-811-314-317-520-2
    Hem-fir#28-011-914-1118-221-17-210-613-416-318-10
    Hem-fir#36-29-011-513-1116-25-68-110-312-614-6
    Southern pineSS8-1114-118-623-8Note b8-1114-118-51-1125-11
    Southern pine#18-713-016-619-322-107-1011-714-917-320-5
    Southern pine#27-611-214-216-1019-106-810-012-815-117-9
    Southern pine#35-98-610-813-015-45-27-79-711-713-9
    Spruce-pine-firSS8-513-317-522-125-78-512-916-219-922-10
    Spruce-pine-fir#18-211-1115-118-521-57-310-813-616-619-2
    Spruce-pine-fir#28-211-1115-118-521-57-310-813-616-619-2
    Spruce-pine-fir#36-29-011-513-1116-25-68-110-312-614-6
    19.2Douglas fir-larchSS8-713-617-922-125-78-712-916-219-922-10
    Douglas fir-larch#17-1111-814-918-020-117-110-513-216-118-8
    Douglas fir-larch#27-711-014-017-119-106-99-1012-615-317-9
    Douglas fir-larch#35-98-510-813-115-25-27-79-711-813-6
    Hem-firSS8-112-916-921-424-88-112-415-719-122-1
    Hem-fir#17-1011-614-717-920-77-010-313-015-1118-5
    Hem-fir#27-410-913-716-719-36-79-712-214-1017-3
    Hem-fir#35-78-310-512-914-95-07-49-411-513-2
    Southern pineSS8-513-317-522-3Note b8-513-316-1020-023-7
    Southern pine#18-011-1015-117-720-117-110-713-515-918-8
    Southern pine#26-1010-212-1115-418-16-19-211-713-916-2
    Southern pine#35-37-99-911-1014-04-86-118-910-712-6
    Spruce-pine-firSS7-1112-516-520-223-47-1111-814-918-020-11
    Spruce-pine-fir#17-510-1113-916-1019-66-89-912-415-117-6
    Spruce-pine-fir#27-510-1113-916-1019-66-89-912-415-117-6
    Spruce-pine-fir#35-78-310-512-914-95-07-49-411-513-2
    24Douglas fir-larchSS8-012-616-219-922-107-1011-514-517-820-5
    Douglas fir-larch#17-110-513-216-118-86-49-411-914-516-8
    Douglas fir-larch#26-99-1012-615-317-96-08-1011-213-815-10
    Douglas fir-larch#35-27-79-711-813-64-76-98-710-512-1
    Hem-firSS7-611-1015-719-122-17-611-013-1117-019-9
    Hem-fir#17-010-313-015-1118-56-39-211-814-316-6
    Hem-fir#26-79-712-214-1017-35-108-710-1013-315-5
    Hem-fir#35-07-49-411-513-24-66-78-410-211-10
    Southern pineSS7-1012-316-220-023-77-1011-1015-017-1121-2
    Southern pine#17-110-713-515-918-86-49-612-014-116-8
    Southern pine#26-19-211-713-916-25-58-210-412-314-6
    Southern pine#34-86-118-910-712-64-26-27-109-611-2
    Spruce-pine-firSS7-411-714-918-020-117-110-513-216-118-8
    Spruce-pine-fir#16-89-912-415-117-65-118-811-013-615-7
    Spruce-pine-fir#26-89-912-415-117-65-118-811-013-615-7
    Spruce-pine-fir#35-07-49-411-513-24-66-78-410-211-10

    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 kPa.

    1. 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. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:

      HC/HRRafter Span Adjustment Factor
      1/30.67
      1/40.76
      1/50.83
      1/60.90
      1/7.5 or less1.00

      where:

      HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

      HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    2. b.Span exceeds 26 feet in length.

    TABLE R802.4.1(4)

    RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load = 30 psf, ceiling attached to rafters, L/Δ = 240)

    RAFTER SPACING (inches)SPECIES AND GRADEDEAD LOAD = 10 psfDEAD LOAD = 20 psf
    2 × 42 × 62 × 82 × 102 × 122 × 42 × 62 × 82 × 102 × 12
    Maximum rafter spansa
    (feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)
    12Douglas fir-larchSS9-114-418-1024-1Note b9-114-418-1024-1Note b
    Douglas fir-larch#18-913-918-222-9Note b8-913-216-820-423-7
    Douglas fir-larch#28-713-617-821-725-18-612-615-1019-422-5
    Douglas fir-larch#37-310-813-616-619-26-69-612-114-917-1
    Hem-firSS8-713-617-1022-9Note b8-713-617-1022-9Note b
    Hem-fir#18-513-317-522-326-08-513-016-620-123-4
    Hem-fir#28-012-716-721-024-48-012-215-418-921-9
    Hem-fir#37-110-513-216-118-86-49-411-914-516-8
    Southern pineSS8-1114-118-623-8Note b8-1114-118-623-8Note b
    Southern pine#18-713-617-1022-3Note b8-713-517-019-1123-7
    Southern pine#28-312-1116-419-522-107-811-714-817-420-5
    Southern pine#36-79-912-415-017-95-118-911-013-515-10
    Spruce-pine-firSS8-513-317-522-3Note b8-513-317-522-3Note b
    Spruce-pine-fir#18-312-1117-021-424-88-312-415-719-122-1
    Spruce-pine-fir#28-312-1117-021-424-88-312-415-719-122-1
    Spruce-pine-fir#37-110-513-216-118-86-49-411-914-516-8
    16Douglas fir-larchSS8-313-017-221-10Note b8-313-017-221-725-1
    Douglas fir-larch#18-012-616-219-922-107-1011-514-517-820-5
    Douglas fir-larch#27-1012-115-418-921-87-510-1013-816-919-5
    Douglas fir-larch#36-49-311-814-316-75-88-310-612-914-10
    Hem-firSS7-1012-316-220-825-17-1012-316-220-824-2
    Hem-fir#17-812-015-1019-622-77-811-314-317-520-2
    Hem-fir#27-311-514-1118-221-17-210-613-416-318-10
    Hem-fir#36-29-011-513-1116-25-68-110-312-614-6
    Southern pineSS8-112-916-1021-6Note b8-112-916-1021-625-11
    Southern pine#17-1012-316-219-322-107-1011-714-917-320-5
    Southern pine#27-611-214-216-1019-106-810-012-815-117-9
    Southern pine#35-98-610-813-015-45-27-79-711-713-9
    Spruce-pine-firSS7-812-015-1020-224-77-812-015-1019-922-10
    Spruce-pine-fir#17-611-915-118-521-57-310-813-616-619-2
    Spruce-pine-fir#27-611-915-118-521-57-310-813-616-619-2
    Spruce-pine-fir#36-29-011-513-1116-25-68-110-312-614-6
    19.2Douglas fir-larchSS7-912-316-120-725-07-912-316-119-922-10
    Douglas fir-larch#17-611-814-918-020-117-110-513-216-118-8
    Douglas fir-larch#27-411-014-017-119-106-99-112-615-317-9
    Douglas fir-larch#35-98-510-813-115-25-27-79-711-813-6
    Hem-firSS7-411-715-319-523-77-411-715-319-122-1
    Hem-fir#17-211-414-717-920-77-016-313-015-1118-5
    Hem-fir#26-1010-913-716-719-36-79-712-214-1017-3
    Hem-fir#35-78-310-512-914-95-07-49-411-513-2
    Southern pineSS7-812-015-1020-224-77-812-015-1020-023-7
    Southern pine#17-411-715-117-720-117-110-713-515-918-8
    Southern pine#26-1010-212-1115-418-16-19-211-713-916-2
    Southern pine#35-37-99-911-1014-04-86-118-910-712-6
    Spruce-pine-firSS7-211-414-1119-023-17-211-414-918-020-11
    Spruce-pine-fir#17-010-1113-916-1019-66-89-912-415-117-6
    Spruce-pine-fir#27-010-1113-916-1019-66-89-912-415-117-6
    Spruce-pine-fir#35-78-310-512-914-95-07-49-411-513-2
    24Douglas fir-larchSS7-311-415-019-122-107-311-414-517-820-5
    Douglas fir-larch#17-010-513-216-118-86-49-411-914-516-8
    Douglas fir-larch#26-99-1012-615-317-96-08-1011-213-815-10
    Douglas fir-larch#35-27-79-711-813-64-76-98-710-512-1
    Hem-firSS6-1010-914-218-021-116-1010-913-1117-019-9
    Hem-fir#16-810-313-015-1118-56-39-211-814-316-6
    Hem-fir#26-49-712-214-1017-35-108-710-1013-315-5
    Hem-fir#35-07-49-411-513-24-66-78-410-211-10
    Southern pineSS7-111-214-818-922-107-111-214-817-1121-2
    Southern pine#16-1010-713-515-918-86-49-612-014-116-8
    Southern pine#26-19-211-713-916-25-58-210-412-314-6
    Southern pine#34-86-118-910-712-64-26-27-109-611-2
    Spruce-pine-firSS6-810-613-1017-820-116-810-513-216-118-8
    Spruce-pine-fir#16-69-912-415-117-65-118-811-013-615-7
    Spruce-pine-fir#26-69-912-415-117-65-118-811-013-615-7
    Spruce-pine-fir#35-07-49-411-513-24-66-78-410-211-10

    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 kPa.

    1. 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. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:

      HC/HRRafter Span Adjustment Factor
      1/30.67
      1/40.76
      1/50.83
      1/60.90
      1/7.5 or less1.00

      where:

      HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

      HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    2. b.Span exceeds 26 feet in length.

    TABLE R802.4.1(5)

    RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load = 50 psf, ceiling not attached to rafters, L/Δ = 180)

    RAFTER SPACING (inches)SPECIES AND GRADEDEAD LOAD = 10 psfDEAD LOAD = 20 psf
    2 × 42 × 62 × 82 × 102 × 122 × 42 × 62 × 82 × 102 × 12
    Maximum rafter spansa
    (feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)
    12Douglas fir-larchSS8-513-317-622-426-08-513-317-321-124-5
    Douglas fir-larch#18-212-015-318-721-77-711-214-117-320-0
    Douglas fir-larch#27-1011-514-517-820-57-310-713-416-418-11
    Douglas fir-larch#36-08-911-013-615-75-68-110-312-614-6
    Hem-firSS8-012-616-621-125-68-012-616-620-423-7
    Hem-fir#17-1011-1015-018-421-37-611-013-1117-019-9
    Hem-fir#27-511-114-017-219-117-010-313-015-1018-5
    Hem-fir#35-108-610-913-215-35-57-1010-012-214-1
    Southern pineSS8-413-117-221-11Note b8-413-117-221-525-3
    Southern pine#18-012-315-618-221-77-711-414-516-1020-0
    Southern pine#27-010-613-415-1018-86-69-912-414-817-3
    Southern pine#35-58-010-112-314-65-07-59-411-413-5
    Spruce-pine-firSS7-1012-316-220-824-17-1012-315-919-322-4
    Spruce-pine-fir#17-811-314-317-520-27-110-513-216-118-8
    Spruce-pine-fir#27-811-314-317-520-27-110-513-216-118-8
    Spruce-pine-fir#35-108-610-913-215-35-57-1010-012-214-1
    16Douglas fir-larchSS7-812-115-1119-922-107-811-1014-1118-321-2
    Douglas fir-larch#17-110-513-216-118-86-79-812-214-1117-3
    Douglas fir-larch#26-99-1012-615-317-96-39-211-714-216-5
    Douglas fir-larch#35-27-79-711-1813-64-97-08-1010-1012-6
    Hem-firSS7-311-515-019-122-17-311-514-517-820-5
    Hem-fir#17-010-313-015-1118-56-69-612-114-917-1
    Hem-fir#26-79-712-214-1017-36-18-1111-313-915-11
    Hem-fir#35-07-49-411-513-24-86-108-810-612-3
    Southern pineSS7-611-1015-719-1123-77-611-1015-718-621-10
    Southern pine#17-110-713-515-918-86-79-1012-514-717-3
    Southern pine#26-19-211-713-916-25-88-510-912-915-0
    Southern pine#34-86-118-910-712-64-46-58-19-1011-7
    Spruce-pine-firSS7-111-214-818-020-117-110-913-815-1119-4
    Spruce-pine-fir#16-89-912-415-117-66-29-011-513-1116-2
    Spruce-pine-fir#26-89-912-415-117-66-29-011-513-1116-2
    Spruce-pine-fir#35-07-49-411-513-24-86-108-810-612-3
    19.2Douglas fir-larchSS7-311-414-918-020-117-310-913-816-819-4
    Douglas fir-larch#16-69-612-014-817-16-08-1011-213-715-9
    Douglas fir-larch#26-29-011-513-1116-25-88-410-912-1115-0
    Douglas fir-larch#34-86-118-910-812-44-46-48-19-1011-5
    Hem-firSS6-1010-914-217-520-26-1010-513-216-118-8
    Hem-fir#16-59-511-1114-616-108-118-811-013-515-7
    Hem-fir#26-08-911-113-715-95-78-110-312-714-7
    Hem-fir#34-76-98-610-512-14-36-37-119-711-2
    Southern pineSS7-111-214-818-321-77-111-214-216-1120-0
    Southern pine#16-69-812-314-417-16-09-011-413-415-9
    Southern pine#25-78-410-712-614-95-27-99-911-713-8
    Southern pine#34-36-48-09-811-54-05-107-48-1110-7
    Spruce-pine-firSS6-810-613-516-519-16-89-1012-515-317-8
    Spruce-pine-fir#16-18-1111-313-915-115-78-310-512-914-9
    Spruce-pine-fir#26-18-1111-313-915-115-78-310-512-914-9
    Spruce-pine-fir#34-76-98-610-512-14-36-37-119-711-2
    24Douglas fir-larchSS6-810-513-216-118-86-79-812-214-1117-3
    Douglas fir-larch#15-108-610-913-215-35-57-1010-012-214-1
    Douglas fir-larch#25-68-110-312-614-65-17-69-511-713-5
    Douglas fir-larch#34-36-27-109-611-13-115-87-38-1010-3
    Hem-firSS6-49-1112-915-718-06-49-411-914-516-8
    Hem-fir#15-98-510-813-015-18-47-99-1012-013-11
    Hem-fir#25-47-109-1112-114-14-117-39-211-313-0
    Hem-fir#34-16-07-79-410-93-105-77-18-710-0
    Southern pineSS6-710-413-816-419-36-710-012-815-217-10
    Southern pine#15-108-811-012-1015-35-58-010-211-1114-1
    Southern pine#25-07-59-511-313-24-76-118-910-512-3
    Southern pine#33-105-87-18-810-33-65-36-78-09-6
    Spruce-pine-firSS6-29-612-014-817-16-08-1011-213-715-9
    Spruce-pine-fir#15-57-1110-112-414-35-07-49-411-513-2
    Spruce-pine-fir#25-57-1110-112-414-35-07-49-411-513-2
    Spruce-pine-fir#34-16-07-79-410-93-105-77-18-710-0

    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 kPa

    1. 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. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:

      HC/HRRafter Span Adjustment Factor
      1/30.67
      1/40.76
      1/50.83
      1/60.90
      1/7.5 or less1.00

      where:

      HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

      HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    2. b.Span exceeds 26 feet in length.

    TABLE R802.4.1(6)

    RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load = 50 psf, ceiling attached to rafters, L/Δ = 240)

    RAFTER SPACING (inches)SPECIES AND GRADEDEAD LOAD = 10 psfDEAD LOAD = 20 psf
    2 × 42 × 62 × 82 × 102 × 122 × 42 × 62 × 82 × 102 × 12
    Maximum rafter spansa
    (feet- inches)(feet- inches)(feet- inches)(feet- inches)(feet- inches)(feet- inches)(feet- inches)(feet- inches)(feet- inches)(feet- inches)
    12Douglas fir-larchSS7-812-115-1120-324-87-812-115-1120-324-5
    Douglas fir-larch#17-511-715-318-721-77-511-214-117-320-0
    Douglas fir-larch#27-311-514-517-820-57-310-713-416-418-11
    Douglas fir-larch#36-08-911-013-615-75-68-110-312-614-6
    Hem-firSS7-311-515-019-223-47-311-515-019-223-4
    Hem-fir#17-111-214-818-421-37-111-013-1117-019-9
    Hem-fir#26-910-814-017-219-116-910-313-015-1018-5
    Hem-fir#35-108-610-913-215-35-57-1010-012-214-1
    Southern pineSS7-611-1015-719-1124-37-611-1015-719-1124-3
    Southern pine#17-311-515-018-221-77-311-414-516-1020-0
    Southern pine#26-1110-613-415-1018-86-69-912-414-817-3
    Southern pine#35-58-010-112-314-65-07-59-411-413-5
    Spruce-pine-firSS7-111-214-818-922-107-111-214-818-922-4
    Spruce-pine-fir#16-1110-1114-317-520-26-1110-513-216-118-8
    Spruce-pine-fir#26-1110-1114-317-520-26-1110-513-216-118-8
    Spruce-pine-fir#35-108-610-913-215-35-57-1010-012-214-1
    16Douglas fir-larchSS7-011-014-518-522-57-011-014-518-321-2
    Douglas fir-larch#16-910-513-216-118-86-79-812-214-1117-3
    Douglas fir-larch#26-79-1012-615-317-96-39-211-714-216-5
    Douglas fir-larch#35-27-79-711-813-64-97-08-1010-1012-6
    Hem-firSS6-710-413-817-521-26-710-413-817-520-5
    Hem-fir#16-510-213-015-1118-56-59-612-114-917-1
    Hem-fir#26-29-712-214-1017-36-18-1111-313-915-11
    Hem-fir#35-07-49-411-513-24-86-108-810-612-3
    Southern pineSS6-1010-914-218-122-06-1010-914-218-121-10
    Southern pine#16-710-413-515-918-86-79-1012-514-717-3
    Southern pine#26-19-211-713-916-25-88-510-912-915-0
    Southern pine#34-86-118-910-712-64-46-58-19-1011-7
    Spruce-pine-firSS6-510-213-417-020-96-510-213-416-819-4
    Spruce-pine-fir#16-49-912-415-117-66-29-011-513-1116-2
    Spruce-pine-fir#26-49-912-415-117-66-29-011-513-1116-2
    Spruce-pine-fir#35-07-49-411-513-24-86-108-810-612-3
    19.2Douglas fir-larchSS6-710-413-717-420-116-710-413-716-819-4
    Douglas fir-larch#16-49-612-014-817-16-08-1011-213-715-9
    Douglas fir-larch#26-29-011-513-1116-25-88-410-712-1115-0
    Douglas fir-larch#34-86-118-910-812-44-46-48-19-1011-5
    Hem-firSS6-29-912-1016-519-116-29-912-1016-118-8
    Hem-fir#16-19-511-1114-616-105-118-811-013-515-7
    Hem-fir#25-98-911-113-715-95-78-110-312-714-7
    Hem-fir#34-76-98-610-512-14-36-37-119-711-2
    Southern pineSS6-510-213-417-020-96-510-213-416-1120-0
    Southern pine#16-29-812-314-417-16-09-011-413-415-9
    Southern pine#25-78-410-712-614-95-27-99-911-713-8
    Southern pine#34-36-48-09-811-54-05-107-48-1110-7
    Spruce-pine-firSS6-19-612-716-019-16-19-612-515-317-8
    Spruce-pine-fir#15-118-1111-313-915-115-78-310-512-914-9
    Spruce-pine-fir#25-118-1111-313-915-115-78-310-512-914-9
    Spruce-pine-fir#34-76-98-610-512-14-36-37-119-711-2
    24Douglas fir-larchSS6-19-712-716-118-86-19-712-214-1117-3
    Douglas fir-larch#15-108-610-913-215-35-57-1010-012-214-1
    Douglas fir-larch#25-68-110-312-614-65-17-69-511-713-5
    Douglas fir-larch#34-36-27-109-611-13-115-87-38-1010-3
    Hem-firSS5-99-111-1115-218-05-99-111-914-515-11
    Hem-fir#15-88-510-813-015-15-47-99-1012-013-11
    Hem-fir#25-47-109-1112-114-14-117-39-211-313-0
    Hem-fir#34-16-07-79-410-93-105-77-18-710-0
    Southern pineSS6-09-512-515-1019-36-09-512-515-217-10
    Southern pine#15-98-811-012-1015-35-58-010-211-1114-1
    Southern pine#25-07-59-511-313-24-76-118-910-512-3
    Southern pine#33-105-87-18-810-33-65-36-78-09-6
    Spruce-pine-firSS5-88-1011-814-817-15-88-1011-213-715-9
    Spruce-pine-fir#15-57-1110-112-414-35-07-49-411-513-2
    Spruce-pine-fir#25-57-1110-112-414-35-07-49-411-513-2
    Spruce-pine-fir#34-16-07-79-410-93-105-77-18-710-0

    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 kPa.

    1. 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. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:

      HC/HRRafter Span Adjustment Factor
      1/30.67
      1/40.76
      1/50.83
      1/60.90
      1/7.5 or less1.00

      where:

      HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

      HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    TABLE R802.4.1(7)

    RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load = 70 psf, ceiling not attached to rafters, L/Δ = 180)

    RAFTER SPACING (inches)SPECIES AND GRADEDEAD LOAD = 10 psfDEAD LOAD = 20 psf
    2 × 42 × 62 × 82 × 102 × 122 × 42 × 62 × 82 × 102 × 12
    Maximum Rafter Spansa
    (feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)
    12Douglas fir-larchSS7-711-1015-819-922-107-711-1015-318-721-7
    Douglas fir-larch#17-110-513-216-118-86-89-1012-515-217-7
    Douglas fir-larch#26-99-1012-615-317-96-49-411-914-516-8
    Douglas fir-larch#35-27-79-711-813-64-107-19-011-012-9
    Hem-firSS7-211-314-918-1022-17-211-314-818-020-10
    Hem-fir#17-010-313-015-1118-56-79-812-315-017-5
    Hem-fir#26-79-712-214-1017-36-29-111-514-016-3
    Hem-fir#35-07-49-411-513-24-96-118-910-912-5
    Southern pineSS7-511-815-419-723-77-511-815-418-1022-3
    Southern pine#17-110-713-515-918-86-910-012-814-1017-7
    Southern pine#26-19-211-713-916-25-98-710-1112-1115-3
    Southern pine#34-86-118-910-712-64-56-68-310-011-10
    Spruce-pine-firSS7-011-014-618-020-117-011-013-1117-019-8
    Spruce-pine-fir#16-89-912-415-117-66-39-211-814-216-6
    Spruce-pine-fir#26-89-912-415-117-66-39-211-814-216-6
    Spruce-pine-fir#35-07-49-411-513-24-96-118-910-912-5
    16Douglas fir-larchSS6-1010-914-017-119-106-1010-513-216-118-8
    Douglas fir-larch#16-29-011-513-1116-25-108-610-913-215-3
    Douglas fir-larch#25-108-710-1013-315-45-68-110-312-614-6
    Douglas fir-larch#34-66-68-310-111-94-36-27-109-611-1
    Hem-firSS6-610-213-516-619-26-610-112-915-718-0
    Hem-fir#16-18-1111-313-916-05-98-510-813-015-1
    Hem-fir#25-88-410-612-1014-115-47-109-1112-114-1
    Hem-fir#34-46-48-19-1011-54-16-07-79-410-9
    Southern pineSS6-910-714-017-420-56-910-713-916-419-3
    Southern pine#16-29-211-813-816-25-108-811-012-1015-3
    Southern pine#25-37-1110-011-1114-05-07-59-511-313-2
    Southern pine#34-16-07-79-210-103-105-87-18-810-3
    Spruce-pine-firSS6-410-012-915-718-16-49-612-014-817-1
    Spruce-pine-fir#15-98-510-813-115-25-57-1110-112-414-3
    Spruce-pine-fir#25-98-510-813-115-25-57-1110-112-414-3
    Spruce-pine-fir#34-46-48-19-1011-54-16-07-79-410-9
    19.2Douglas fir-larchSS6-610-112-915-718-16-69-612-014-817-1
    Douglas fir-larch#15-78-310-512-914-95-47-99-1012-013-11
    Douglas fir-larch#25-47-109-1112-114-05-07-49-411-513-2
    Douglas fir-larch#34-16-07-79-310-83-105-77-18-810-1
    Hem-firSS6-19-712-415-117-46-19-211-814-215-5
    Hem-fir#15-78-210-312-714-75-37-89-811-1013-9
    Hem-fir#25-27-79-711-913-74-117-29-111-112-10
    Hem-fir#34-05-107-49-010-53-95-66-118-69-10
    Southern pineSS6-410-013-215-1018-86-49-1012-614-1117-7
    Southern pine#15-88-510-812-514-95-47-1110-011-913-11
    Southern pine#24-107-39-210-1012-94-66-108-810-312-1
    Southern pine#33-85-66-118-49-113-65-26-67-119-4
    Spruce-pine-firSS6-09-211-814-316-65-118-811-013-515-7
    Spruce-pine-fir#15-37-89-911-1113-105-07-39-211-313-0
    Spruce-pine-fir#25-37-89-911-1113-105-07-39-211-313-0
    Spruce-pine-fir#34-05-107-49-010-53-95-66-118-69-10
    24Douglas fir-larchSS6-09-011-513-1116-25-108-610-913-215-3
    Douglas fir-larch#15-07-49-411-513-24-96-118-910-912-5
    Douglas fir-larch#24-97-08-1010-1012-64-66-78-410-211-10
    Douglas fir-larch#33-85-46-98-39-73-55-06-47-99-10
    Hem-firSS5-88-811-013-613-115-78-310-512-412-4
    Hem-fir#15-07-39-211-313-04-86-108-810-712-4
    Hem-fir#24-86-98-710-612-24-46-58-19-1111-6
    Hem-fir#33-75-26-78-19-43-44-116-37-78-10
    Southern pineSS5-119-311-1114-216-85-118-1011-213-415-9
    Southern pine#15-07-69-611-113-24-97-19-010-612-5
    Southern pine#24-46-58-29-911-54-16-17-99-210-9
    Southern pine#33-44-116-27-68-103-14-75-107-18-4
    Spruce-pine-firSS5-68-310-512-914-95-47-99-1012-012-11
    Spruce-pine-fir#14-86-118-910-812-44-56-68-310-011-8
    Spruce-pine-fir#24-86-118-910-812-44-56-68-310-011-8
    Spruce-pine-fir#33-75-26-78-19-43-44-116-37-78-10

    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 kPa.

    1. 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. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:

      HC/HRRafter Span Adjustment Factor
      1/30.67
      1/40.76
      1/50.83
      1/60.90
      1/7.5 or less1.00

      where:

      HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

      HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    TABLE R802.4.1(8)

    RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load = 70 psf, ceiling attached to rafters, L/Δ = 240)

    RAFTER SPACING (inches)SPECIES AND GRADEDEAD LOAD = 10 psfDEAD LOAD = 20 psf
    2 × 42 × 62 × 82 × 102 × 122 × 42 × 62 × 82 × 102 × 12
    Maximum rafter spansa
    (feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)(feet - inches)
    12Douglas fir-larchSS6-1010-914-318-222-16-1010-914-318-221-7
    Douglas fir-larch#16-710-513-216-118-86-79-1012-515-217-7
    Douglas fir-larch#26-69-1012-615-317-96-49-411-914-516-8
    Douglas fir-larch#35-27-79-711-813-64-107-19-011-012-9
    Hem-firSS6-610-213-517-220-106-610-213-517-220-10
    Hem-fir#16-410-013-015-1118-56-49-812-315-017-5
    Hem-fir#26-19-612-214-1017-36-19-111-514-016-3
    Hem-fir#35-07-49-411-513-24-96-118-910-912-5
    Southern pineSS6-910-714-017-1021-86-910-714-017-1021-8
    Southern pine#16-610-213-515-918-86-610-012-814-1017-7
    Southern pine#26-19-211-713-916-25-98-710-1112-1115-3
    Southern pine#34-86-118-910-712-64-56-68-310-011-10
    Spruce-pine-firSS6-410-013-216-920-56-410-013-216-919-8
    Spruce-pine-fir#16-29-912-415-117-66-29-211-814-216-6
    Spruce-pine-fir#26-29-912-415-117-66-29-211-814-216-6
    Spruce-pine-fir#35-07-49-411-513-24-96-118-910-912-5
    16Douglas fir-larchSS6-39-1012-1116-619-106-39-1012-1116-118-8
    Douglas fir-larch#16-09-011-513-1116-25-108-610-913-215-3
    Douglas fir-larch#25-108-710-1013-315-45-68-110-312-614-6
    Douglas fir-larch#34-66-68-310-111-94-36-27-109-611-1
    Hem-firSS5-119-312-215-718-115-119-312-215-718-0
    Hem-fir#15-98-1111-313-916-05-98-510-813-015-1
    Hem-fir#25-68-410-612-1014-115-47-109-1112-114-1
    Hem-fir#34-46-48-19-1011-54-16-07-79-410-9
    Southern pineSS6-19-712-816-219-86-19-712-816-219-3
    Southern pine#15-119-211-813-816-25-108-811-012-1015-3
    Southern pine#25-37-1110-011-1114-05-07-59-511-313-2
    Southern pine#34-16-07-79-210-103-105-87-18-810-3
    Spruce-pine-firSS5-99-111-1115-318-15-99-111-1114-817-1
    Spruce-pine-fir#15-88-510-813-115-25-57-1110-112-414-3
    Spruce-pine-fir#25-88-510-813-115-25-57-1110-112-414-3
    Spruce-pine-fir#34-46-48-19-1011-54-16-07-79-410-9
    19.2Douglas fir-larchSS5-109-312-215-618-15-109-312-014-817-1
    Douglas fir-larch#15-78-310-512-914-95-47-99-1012-013-11
    Douglas fir-larch#25-47-109-1112-114-05-07-49-411-513-2
    Douglas fir-larch#34-16-07-79-310-83-105-77-18-810-1
    Hem-firSS5-68-811-614-817-45-68-811-614-215-5
    Hem-fir#15-58-210-312-714-75-37-89-811-1013-9
    Hem-fir#25-27-79-711-913-74-117-29-111-112-10
    Hem-fir#34-05-107-49-010-53-95-66-118-69-10
    Southern pineSS5-99-111-1115-318-65-99-111-1114-1117-7
    Southern pine#15-68-510-812-514-95-47-1110-011-913-11
    Southern pine#24-107-39-210-1012-94-66-108-810-312-1
    Southern pine#33-85-66-118-49-113-65-26-67-119-4
    Spruce-pine-firSS5-58-611-314-316-65-58-611-013-515-7
    Spruce-pine-fir#15-37-89-911-1113-105-07-39-211-313-0
    Spruce-pine-fir#25-37-89-911-1113-105-07-39-211-313-0
    Spruce-pine-fir#34-05-107-49-010-53-95-66-118-69-10
    24Douglas fir-larchSS5-58-711-313-1116-25-58-610-913-215-3
    Douglas fir-larch#15-07-49-411-513-24-96-118-910-912-5
    Douglas fir-larch#24-97-08-1010-1012-64-66-78-410-211-10
    Douglas fir-larch#33-85-46-98-39-73-55-06-47-99-0
    Hem-firSS5-28-110-813-613-115-28-110-512-412-4
    Hem-fir#15-07-39-211-313-04-86-108-810-712-4
    Hem-fir#24-86-98-710-612-24-46-58-19-1111-6
    Hem-fir#33-75-26-78-19-43-44-116-37-78-10
    Southern pineSS5-48-511-114-216-85-48-511-113-415-9
    Southern pine#15-07-69-611-113-24-97-19-010-612-5
    Southern pine#24-46-58-29-911-54-16-17-99-210-9
    Southern pine#33-44-116-27-68-103-14-75-107-18-4
    Spruce-pine-firSS5-07-1110-512-914-95-07-99-1012-012-11
    Spruce-pine-fir#14-86-118-910-812-44-56-68-310-011-8
    Spruce-pine-fir#24-86-118-910-812-44-56-68-310-011-8
    Spruce-pine-fir#33-75-26-78-19-43-44-116-37-78-10

    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 kPa.

    1. 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. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:

      HC/HRRafter Span Adjustment Factor
      1/30.67
      1/40.76
      1/50.83
      1/60.90
      1/7.5 or less1.00

      where:

      HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

      HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    R802.4.2Framing details.

    Rafters shall be framed not more than 11/2 inches (38 mm) offset from each other to a ridge board or directly opposite from 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.

    R802.4.3Hips and valleys.

    Hip and valley rafters shall be not less than 2 inches (51 mm) nominal in 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.

    R802.4.4Rafter supports.

    Where the roof pitch is less than 3:12 (25-percent slope), structural members that support rafters, such as ridges, hips and valleys, shall be designed as beams, and bearing shall be provided for rafters in accordance with Section R802.6.

    R802.4.5Purlins.

    Installation of purlins to reduce the span of rafters is permitted as shown in Figure R802.4.5. Purlins shall be sized not 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 (0.79 rad) 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).

    For SI: 1 inch = 25.4 mm, 1 foot = 305 mm, 1 degree = 0.018 rad.

    HC = Height of ceiling joists or rafter ties measured vertically above the top of rafter support walls.

    HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    FIGURE R802.4.5

    BRACED RAFTER CONSTRUCTION

    R802.4.6Collar ties.

    Where collar ties are used to connect opposing rafters, they shall be located in the upper third of the attic space and fastened in accordance with Table R602.3(1). Collar ties shall be not less than 1 inch by 4 inches (25 mm × 102 mm) nominal, spaced not more than 4 feet (1220 mm) on center. Ridge straps in accordance with Table R602.3(1) shall be permitted to replace collar ties.

    R802.5Ceiling joists.

    Ceiling joists shall be continuous across the structure or securely joined where they meet over interior partitions in accordance with Table R802.5.2.

    R802.5.1Ceiling joist size.

    Ceiling joists shall be sized based on the joist spans in Tables R802.5.1(1) and R802.5.1(2). For other grades and species and for other loading conditions, refer to the AWC STJR.

    TABLE R802.5.1(1)

    CEILING JOIST SPANS FOR COMMON LUMBER SPECIES (Uninhabitable attics without storage, live load = 10 psf, L/Δ = 240)

    CEILING JOIST SPACING (inches)SPECIES AND GRADEDEAD LOAD = 5 psf
    2 × 42 × 62 × 82 × 10
    Maximum ceiling joist spans
    (feet - inches)(feet - inches)(feet - inches)(feet - inches)
    12Douglas fir-larchSS13-220-8Note aNote a
    Douglas fir-larch#112-819-11Note aNote a
    Douglas fir-larch#212-519-625-8Note a
    Douglas fir-larch#311-116-320-725-2
    Hem-firSS12-519-625-8Note a
    Hem-fir#112-219-125-2Note a
    Hem-fir#211-718-224-0Note a
    Hem-fir#310-1015-1020-124-6
    Southern pineSS12-1120-3Note aNote a
    Southern pine#112-519-625-8Note a
    Southern pine#211-1018-824-7Note a
    Southern pine#310-114-1118-922-9
    Spruce-pine-firSS12-219-125-2Note a
    Spruce-pine-fir#111-1018-824-7Note a
    Spruce-pine-fir#211-1018-824-7Note a
    Spruce-pine-fir#310-1015-1020-124-6
    16Douglas fir-larchSS11-1118-924-8Note a
    Douglas fir-larch#111-618-123-10Note a
    Douglas fir-larch#211-317-823-4Note a
    Douglas fir-larch#39-714-117-1021-9
    Hem-firSS11-317-823-4Note a
    Hem-fir#111-017-422-10Note a
    Hem-fir#210-616-621-9Note a
    Hem-fir#39-513-917-521-3
    Southern pineSS11-918-524-3Note a
    Southern pine#111-317-823-10Note a
    Southern pine#210-916-1121-725-7
    Southern pine#38-912-1116-319-9
    Spruce-pine-firSS11-017-422-10Note a
    Spruce-pine-fir#110-916-1122-4Note a
    Spruce-pine-fir#210-916-1122-4Note a
    Spruce-pine-fir#39-513-917-521-3
    19.2Douglas fir-larchSS11-317-823-3Note a
    Douglas fir-larch#110-1017-022-5Note a
    Douglas fir-larch#210-716-821-426-0
    Douglas fir-larch#38-912-1016-319-10
    Hem-firSS10-716-821-11Note a
    Hem-fir#110-416-421-6Note a
    Hem-fir#29-1115-720-625-3
    Hem-fir#38-712-615-1019-5
    Southern -pineSS11-017-422-10Note a
    Southern pine#110-716-822-0Note a
    Southern pine#210-215-719-823-5
    Southern pine#38-011-914-1018-0
    Spruce-pine-firSS10-416-421-6Note a
    Spruce-pine-fir#110-215-1121-025-8
    Spruce-pine-fir#210-215-1121-025-8
    Spruce-pine-fir#38-712-615-1019-5
    24Douglas fir-larchSS10-516-421-7Note a
    Douglas fir-larch#110-015-920-124-6
    Douglas fir-larch#29-1015-019-123-3
    Douglas fir-larch#37-1011-614-717-9
    Hem-firSS9-1015-620-5Note a
    Hem-fir#19-815-219-1024-3
    Hem-fir#29-214-518-622-7
    Hem-fir#37-811-214-217-4
    Southern pineSS10-316-121-2Note a
    Southern pine#19-1015-620-524-0
    Southern pine#29-313-1117-720-11
    Southern pine#37-210-613-316-1
    Spruce-pine-firSS9-815-219-1125-5
    Spruce-pine-fir#19-514-918-922-11
    Spruce-pine-fir#29-514-918-922-11
    Spruce-pine-fir#37-811-214-217-4

    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 kPa.

    1. a.Span exceeds 26 feet in length.

    TABLE R802.5.1(2)

    CEILING JOIST SPANS FOR COMMON LUMBER SPECIES (Uninhabitable attics with limited storage, live load = 20 psf, L/Δ = 240)

    CEILING JOIST SPACING (inches)SPECIES AND GRADEDEAD LOAD = 10 psf
    2 × 42 × 62 × 82 × 10
    Maximum ceiling joist spans
    (feet - inches)(feet - inches)(feet - inches)(feet - inches)
    12Douglas fir-larchSS10-516-421-7Note a
    Douglas fir-larch#110-015-920-124-6
    Douglas fir-larch#29-1015-019-123-3
    Douglas fir-larch#37-1011-614-717-9
    Hem-firSS9-1015-620-5Note a
    Hem-fir#19-815-219-1024-3
    Hem-fir#29-214-518-622-7
    Hem-fir#37-811-214-217-4
    Southern pineSS10-316-121-2Note a
    Southern pine#19-1015-620-524-0
    Southern pine#29-313-1117-720-11
    Southern pine#37-210-613-316-1
    Spruce-pine-firSS9-815-219-1125-5
    Spruce-pine-fir#19-514-918-922-11
    Spruce-pine-fir#29-514-918-922-11
    Spruce-pine-fir#37-811-214-217-4
    16Douglas fir-larchSS9-614-1119-725-0
    Douglas fir-larch#19-113-917-521-3
    Douglas fir-larch#28-1113-016-620-2
    Douglas fir-larch#36-109-1112-715-5
    Hem-firSS8-1114-118-623-8
    Hem-fir#18-913-717-221-0
    Hem-fir#28-412-816-019-7
    Hem-fir#36-89-812-415-0
    Southern pineSS9-414-719-324-7
    Southern pine#18-1114-017-920-9
    Southern pine#28-012-015-318-1
    Southern pine#36-29-211-614-0
    Spruce-pine-firSS8-913-918-123-1
    Spruce-pine-fir#18-712-1016-319-10
    Spruce-pine-fir#28-712-1016-319-10
    Spruce-pine-fir#36-89-812-415-0
    19.2Douglas fir-larchSS8-1114-018-523-7
    Douglas fir-larch#18-712-615-1019-5
    Douglas fir-larch#28-211-1115-118-5
    Douglas fir-larch#36-29-111-614-1
    Hem-firSS8-513-317-522-3
    Hem-fir#18-312-415-819-2
    Hem-fir#27-1011-714-817-10
    Hem-fir#36-18-1011-313-8
    Southern pineSS8-913-918-223-1
    Southern pine#18-512-916-218-11
    Southern pine#27-411-013-1116-6
    Southern pine#35-88-410-612-9
    Spruce-pine-firSS8-312-1117-121-8
    Spruce-pine-fir#18-011-914-1018-2
    Spruce-pine-fir#28-011-914-1018-2
    Spruce-pine-fir#36-18-1011-313-8
    24Douglas fir-larchSS8-313-017-221-3
    Douglas fir-larch#17-811-214-217-4
    Douglas fir-larch#27-310-813-616-5
    Douglas fir-larch#35-78-110-312-7
    Hem-firSS7-1012-316-220-6
    Hem-fir#17-711-114-017-1
    Hem-fir#27-110-413-116-0
    Hem-fir#35-57-1110-012-3
    Southern pineSS8-112-916-1021-6
    Southern pine#17-811-514-616-11
    Southern pine#26-79-1012-614-9
    Southern pine#35-17-59-511-5
    Spruce-pine-firSS7-812-015-1019-5
    Spruce-pine-fir#17-210-613-316-3
    Spruce-pine-fir#27-210-613-316-3
    Spruce-pine-fir#35-57-1110-012-3

    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 kPa.

    1. a.Span exceeds 26 feet in length.

    R802.5.2Ceiling joist and rafter connections.

    Where ceiling joists run parallel to rafters, they shall be connected to rafters at the top wall plate in accordance with Table R802.5.2. Where ceiling joists are not connected to the rafters at the top wall plate, they shall be installed in the bottom third of the rafter height in accordance with Figure R802.4.5 and Table R802.5.2. Where the ceiling joists are installed above the bottom third of the rafter height, the ridge shall be designed as a beam.Where ceiling joists do not run parallel to rafters, the ceiling joists shall be connected to top plates in accordance with Table R602.3(1). Each rafter shall be tied across the structure with a rafter tie or a 2-inch by 4-inch (51 mm × 102 mm) kicker connected to the ceiling diaphragm with nails equivalent in capacity to Table R802.5.2.

    TABLE R802.5.2

    RAFTER/CEILING JOIST HEEL JOINT CONNECTIONSa, b, c, d, e, g

    RAFTER SLOPERAFTER SPACING (inches)GROUND SNOW LOAD (psf)
    20f305070
    Roof span (feet)
    12202836122028361220283612202836
    Required number of 16d common nailsa, b per heel joint splicesc, d, e
    3:121246810468115812156111520
    1658101358111461115208142026
    2471115197111621916233012213039
    4:12123568356846911581215
    1646810468115812156111520
    2458121559121671217229162329
    5:121234563457357947912
    163568357947912591216
    244791247101361014187131823
    7:12123445334534573579
    1634563456357946911
    2435793579471013591317
    9:12123344333433453457
    163445334534573579
    243467346736810471013
    12:12123333333333343345
    163344333433453457
    2434453346346836810

    For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.

    1. a.40d box nails shall be permitted to be substituted for 16d common nails.

    2. b.Nailing requirements shall be permitted to be reduced 25 percent if nails are clinched.

    3. c.Heel joint connections are not required where the ridge is supported by a load-bearing wall, header or ridge beam.

    4. d.Where intermediate support of the rafter is provided by vertical struts or purlins to a load-bearing wall, the tabulated heel joint connection requirements shall be permitted to be reduced proportionally to the reduction in span.

    5. e.Equivalent nailing patterns are required for ceiling joist to ceiling joist lap splices.

    6. f.Applies to roof live load of 20 psf or less.

    7. g.Tabulated heel joint connection requirements assume that ceiling joists or rafter ties are located at the bottom of the attic space. Where ceiling joists or rafter ties are located higher in the attic, heel joint connection requirements shall be increased by the following factors:

      HC/HRHeel Joint Connection Adjustment Factor
      1/31.5
      1/41.33
      1/51.25
      1/61.2
      1/10 or less1.11

      where:

      HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

      HR = Height of roof ridge measured vertically above the top of the rafter support walls.

    R802.5.2.1Ceiling joists lapped.

    Ends of ceiling joists shall be lapped not less than 3 inches (76 mm) or butted over bearing partitions or beams and toenailed to the bearing member. Where ceiling joists are used to provide resistance to rafter thrust, lapped joists shall be nailed together in accordance with Table R802.5.2 and butted joists shall be tied together in a manner to resist such thrust. Joists that do not resist thrust shall be permitted to be nailed in accordance with Table R602.3(1). Wood structural panel roof sheathing, in accordance with Table R503.2.1.1(1), shall not cantilever more than 9 inches (229 mm) beyond the gable endwall unless supported by gable overhang framing.

    R802.5.2.2Rafter ties.

    Wood rafter ties shall be not less than 2 inches by 4 inches (51 mm × 102 mm) installed in accordance with Table R802.5.2 at each rafter. Other approved rafter tie methods shall be permitted.

    R802.5.2.3Blocking.

    Blocking shall be not less than utility grade lumber.

    R802.6Bearing.

    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. The bearing on masonry or concrete shall be direct, or a sill plate of 2-inch (51 mm) minimum nominal thickness shall be provided under the rafter or ceiling joist. The sill plate shall provide a minimum nominal bearing area of 48 square inches (30 865 mm2).

    R802.6.1Finished 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 finished ceiling material shall be installed directly above the top plate of bearing walls if the compressive strength of the finished 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 not less than one-half the width of the top plate. It shall be of material capable of transmitting the loads transferred through it.

    R802.7Cutting, drilling and notching.

    Structural roof members shall not be cut, bored or notched in excess of the limitations specified in this section.

    R802.7.1Sawn lumber.

    Cuts, notches and holes in solid lumber joists, rafters, blocking and beams shall comply with the provisions of Section R502.8.1 except that cantilevered portions of rafters shall be permitted in accordance with Section R802.7.1.1.

    R802.7.1.1Cantilevered portions of rafters.

    Notches on cantilevered portions of rafters are permitted provided the dimension of the remaining portion of the rafter is not less than 31/2 inches (89 mm) and the length of the cantilever does not exceed 24 inches (610 mm) in accordance with Figure R802.7.1.1.

    For SI: 1 inch = 25.4 mm.

    FIGURE R802.7.1.1

    RAFTER NOTCH

    R802.7.1.2Ceiling joist taper cut.

    Taper cuts at the ends of the ceiling joist shall not exceed one-fourth the depth of the member in accordance with Figure R802.7.1.2.

    FIGURE R802.7.1.2

    CEILING JOIST TAPER CUT

    R802.7.2Engineered wood products.

    Cuts, notches and holes bored in trusses, structural composite lumber, structural glue-laminated members, cross-laminated timber members or I-joists are prohibited except where permitted by the manufacturer’s recommendations or where the effects of such alterations are specifically considered in the design of the member by a registered design professional.

    R802.8Lateral support.

    Roof framing members 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. For roof rafters with ceiling joists attached in accordance with Table R602.3(1), the depth-to-thickness ratio for the total assembly shall be determined using the combined thickness of the rafter plus the attached ceiling joist.

    Exception: Roof trusses shall be braced in accordance with Section R802.10.3.

    R802.8.1Bridging.

    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 mm by 76 mm) wood strip nailed across the rafters or ceiling joists at intervals not exceeding 8 feet (2438 mm).

    R802.9Framing of openings.

    Openings in roof and ceiling framing shall be framed with header and trimmer joists. Where the header joist span does not exceed 4 feet (1219 mm), the header joist shall be permitted to be a single member the same size as the ceiling joist or rafter. Single trimmer joists shall be permitted to be used to carry a single header joist that is located within 3 feet (914 mm) of the trimmer joist bearing. Where 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 where 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).

    R802.10Wood trusses.

    R802.10.1Truss design drawings.

    Truss design drawings, prepared in conformance to Section R802.10.1, shall be provided to the building official and approved prior to installation. Truss design drawings shall be provided with the shipment of trusses delivered to the job site. Truss design drawings shall include, at a minimum, the following information:

    1. 1.Slope or depth, span and spacing.

    2. 2.Location of all joints.

    3. 3.Required bearing widths.

    4. 4.Design loads as applicable.

      1. 4.1.Top chord live load (as determined from Section R301.6).

      2. 4.2.Top chord dead load.

      3. 4.3.Bottom chord live load.

      4. 4.4.Bottom chord dead load.

      5. 4.5.Concentrated loads and their points of application.

      6. 4.6.Controlling wind and earthquake loads.

    5. 5.Adjustments to lumber and joint connector design values for conditions of use.

    6. 6.Each reaction force and direction.

    7. 7.Joint connector type and description such as size, thickness or gage and the dimensioned location of each joint connector except where symmetrically located relative to the joint interface.

    8. 8.Lumber size, species and grade for each member.

    9. 9.Connection requirements for:

      1. 9.1.Truss to girder-truss.

      2. 9.2.Truss ply to ply.

      3. 9.3.Field splices.

    10. 10.Calculated deflection ratio or maximum description for live and total load.

    11. 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. 12.Required permanent truss member bracing location.

    R802.10.2Design.

    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.

    R802.10.2.1Applicability limits.

    The provisions of this section shall control the design of truss roof framing where snow controls for buildings that are not greater than 60 feet (18 288 mm) in length perpendicular to the joist, rafter or truss span, not greater than 36 feet (10 973 mm) in width parallel to the joist, rafter or truss span, not more than three stories above grade plane in height, and have roof slopes not smaller than 3:12 (25-percent slope) or greater than 12:12 (100-percent slope). Truss roof framing constructed in accordance with the provisions of this section shall be limited to sites subjected to a maximum design wind speed of 140 miles per hour (63 m/s), Exposure B or C, and a maximum ground snow load of 70 psf (3352 Pa). For consistent loading of all truss types, roof snow load is to be computed as: 0.7 pg.

    R802.10.3Bracing.

    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 accepted industry practice such as the SBCA Building Component Safety Information (BCSI) Guide to Good Practice for Handling, Installing & Bracing of Metal Plate Connected Wood Trusses.

    R802.10.4Alterations 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 such as 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.

    R802.11Roof tie-down.

    TABLE R802.11

    RAFTER OR TRUSS UPLIFT CONNECTION FORCES FROM WIND (ASD) (POUNDS PER CONNECTION)a, b, c, d, e, f, g, h

    RAFTER OR TRUSS SPACINGROOF SPAN(feet)EXPOSURE B
    Ultimate Design Wind Speed VULT (mph)
    110115120130140
    Roof PitchRoof PitchRoof PitchRoof PitchRoof Pitch
    < 5:12≥ 5:12< 5:12≥ 5:12< 5:12≥ 5:12< 5:12≥ 5:12< 5:12≥ 5:12
    12″ o.c.124843595370649588122113
    18595274668981122112157146
    247162897910898149137192178
    2879699988121109167153216