Browse
  • CHAPTER 8
    ROOF-CEILING CONSTRUCTION 

    SECTION R801
    GENERAL

    R801.1 Application.

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

    R801.2 Requirements.

    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.

    R801.3 Roof drainage.

    In areas where expansive 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.

    SECTION R802
    WOOD ROOF FRAMING 

    R802.1 General.

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

    R802.1.1 Sawn 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.

    R802.1.1.1 End-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.

    R802.1.2 Structural glued laminated timbers.

    Glued laminated timbers shall be manufactured and identified as required in ANSI/AITC A190.1 and ASTM D 3737.

    R802.1.3 Structural log members.

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

    R802.1.4 Structural composite lumber.

    Structural capacities for structural composite lumber shall be established and monitored in accordance with ASTM D 5456.

    R802.1.5 Fire-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 E 84 or UL 723, a listed flame spread index of 25 or less and shows no 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.

    R802.1.5.1 Pressure 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).

    R802.1.5.2 Other 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.

    R802.1.5.3 Testing.

    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.

    R802.1.5.4 Labeling.

    Fire-retardant-treated lumber and wood structural panels 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 D 2898).

    R802.1.5.5 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 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.

    R802.1.5.6 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.

    R802.1.5.7 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 ASTM D 6841. 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.

    R802.1.5.8 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 not an increase in the listed flame spread index as defined in Section R802.1.5 when subjected to ASTM D 2898.

    R802.1.5.9 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 R802.1.5.6 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.

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

    R802.1.6 Cross-laminated timber.

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

    R802.1.7 Engineered wood rim board.

    Engineered wood rim boards shall conform to ANSI/APA PRR 410 or shall be evaluated in accordance with ASTM D 7672. Structural capacities shall be in accordance with ANSI/APA PRR 410 or established in accordance with ASTM D 7672. Rim boards conforming to ANSI/APA PRR 410 shall be marked in accordance with that standard.

    R802.2 Design and construction.

    The framing details required in Section R802 apply to roofs having a minimum slope of three units vertical in 12 units horizontal (25-percent slope) or greater. Roof-ceilings 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. Components of roof-ceilings shall be fastened in accordance with Table R602.3(1).

    R802.3 Framing details.

    Rafters shall be framed not more than 11/2-inches (38 mm) offset from each other to ridge board or directly opposite from each other with a gusset plate as a tie. Ridge board shall be not less than 1-inch (25 mm) nominal thickness and not less in depth than the cut end of the rafter. At 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 Table R802.5.1(9), and the rafter shall be nailed to the top wall plate in accordance with Table R602.3(1). Ceiling joists shall be continuous or securely joined in accordance with Table R802.5.1(9) where they meet over interior partitions and are nailed to adjacent rafters to provide a continuous tie across the building where such joists are parallel to the rafters.

    Where ceiling joists are not connected to the rafters at the top wall plate, joists connected higher in the attic shall be installed as rafter ties, or rafter ties shall be installed to provide a continuous tie. Where ceiling joists are not parallel to rafters, rafter ties shall be installed. Rafter ties shall be not less than 2 inches by 4 inches (51 mm by 102 mm) (nominal), installed in accordance with the connection requirements in Table R802.5.1(9), or connections of equivalent capacities shall be provided. Where ceiling joists or rafter ties are not provided, the ridge formed by these rafters shall be supported by a wall or girder designed in accordance with accepted engineering practice.

    Collar ties or ridge straps to resist wind uplift shall be connected in the upper third of the attic space in accordance with Table R602.3(1).

    Collar ties shall be not less than 1 inch by 4 inches (25 mm by 102 mm) (nominal), spaced not more than 4 feet (1219 mm) on center.

    R802.3.2 Ceiling 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 R802.5.1(9) 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).

    R802.3.3 Blocking.

    Blocking shall be a minimum of utility grade lumber.

    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 AWC STJR.

    TABLE R802.4(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 R802.4(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 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 AWC STJR. The span of each rafter shall be measured along the horizontal projection of the rafter.

    R802.5.1 Purlins.

    Installation of purlins to reduce the span of rafters is permitted as shown in Figure R802.5.1. 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).

    TABLE R802.5.1(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#27-411-010-1116-619-66-49-612-114-416-10
    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 R802.5.1(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 R802.5.1(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 R802.5.1(4)

    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 R802.5.1(5)

    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 R802.5.1(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 R802.5.1(7)

    RAFTER SPANS FOR 70 PSF GROUND SNOW LOAD (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#26-19-211-713-916-25-9