Where all rafters are placed directly opposite each other or are offset at the ridge board by less than the thickness of the rafter, the ridge board shall have a nominal thickness of at least 1 inch.
Where one or more rafters are offset at the ridge board by more than the thickness of the rafter, the ridge board shall have a nominal thickness of at least 2 inches.
Rafters shall be attached to ridge beams using engineered clips, straps or hangers or the connection shall be designed through structural analysis.
The required bearing for wood rafters shall be in accordance with the NDS adopted in Table 320.24-6m, except in no case shall the bearing be less than 1 1/2 inches on wood or metal or less than 3 inches on masonry or concrete.
Overhangs at gable end walls of more than 12 inches shall be provided with ladders which extend into the structure a distance no less than the length of the overhang.
The interior end of each ladder shall be attached to a rafter or truss with a hanger.
SPS 321.27 Note
Note: For the purposes of this section, a ladder is defined as a perpendicular projection extending beyond the face of the wall below.
Ceiling joists shall be nailed to exterior walls and to the ends of rafters.
Ends of ceiling joists shall be lapped at least 3 inches and be fastened either with 3-16d nails or in accordance with the floor joist requirements under s. SPS 321.22 (4) (a) 1. d.
SPS 321.27 Note
See the fastener table in the ch. SPS 325 Appendix A
for a nailing schedule for ceiling joists.
Where ceiling joists are placed at right angles to the rafters, the lookout joist or ties shall be fastened to the parallel ceiling joists or rafters using engineered clips, straps or hangers or the connection shall be designed through structural analysis.
Where no bearing is provided under valley rafters at the intersection of 2 roof areas, the valley rafters shall be doubled in thickness and shall be at least 2 inches deeper than the required common rafter to permit full bearing at the beveled end.
Where ridges are provided at different elevations, vertical support shall be provided for the interior end of the lower ridge board or ridge beam.
Where no bearing is provided under hip rafters, the hip rafters shall be of the same thickness as common rafters and shall be at least 2 inches deeper than required to permit full contact with the jack rafter.
Metal plate connected wood roof trusses shall be designed in accordance with TPI 1 and the NDS adopted under s. SPS 320.24
If connection is provided to stabilize a non-load bearing wall, a slotted expansion joint or clip shall be used.
Notching and boring of beams or girders is prohibited unless determined through structural analysis.
Notches located in the top or bottom of ceiling joists and rafters are prohibited from all of the following:
Where ceiling joists or rafters are notched at the ends, the notch may not exceed ¼
the depth of the member.
Bird mouth cuts may not exceed 1/3
the depth of the rafter unless the seat cut bears fully on the wall plate.
Holes bored within 2 inches of the top or bottom of ceiling joists or rafters may not be located in the middle 1/3
of the span of the member.
The distance between adjacent holes may not be less than the diameter of the larger hole.
Engineered wood products.
Notching or boring of engineered wood products shall be done in accordance with the manufacturer's instructions provided those instructions were developed through structural analysis or product testing.
The allowable loads and spans for structural sheathing shall be in accordance with the grade stamp on the panel.
Where the rafter spacing is 24 inches on center or less, roof boards may be used that have a minimum thickness of 5/8
-inch for solid sheathing and 3/4
-inch for spaced sheathing.
Where the rafter spacing is greater than 24 inches on center, roof boards shall be tongue and groove, at least 1.5 inches thick.
Roof planks shall be tongue and groove or splined and at least 2 inches, nominal, in thickness.
Planks shall terminate over beams unless the joints are end matched.
The planks shall be laid so that no continuous line of joints will occur except at points of support.
SPS 321.27 History
Cr. Register, November, 1979, No. 287
, eff. 6-1-80; am (3) (a), Register, January, 1989, No. 397
, eff. 2-1-89; r. and recr. (1), am. (3) (a), Register, March, 1992, No. 435
, eff. 4-1-92; r. and recr. (3) (a), Register, November, 1995, No. 479
, eff. 12-1-95; r. and recr. (3) (a) 1. and 2. c., Register, January, 1999, No. 517
, eff. 2-1-99; am. (3) (a) 1. a., Register, March, 2001, No. 543
, eff. 4-1-01; CR 02-077
: r. and recr. (3) (b) Register May 2003 No. 569
, eff. 8-1-03; CR 08-043
: r. and recr. Register March 2009 No. 639
, eff. 4-1-09; correction in (1) (a), (c), (4) (d), (5) (b), (7) (a) made under s. 13.92 (4) (b) 7.
, Stats., Register December 2011 No. 672
; CR 15-041
: am. (4) (d) Register December 2015 No. 720
, eff. 1-1-16.
SPS 321.28 Weather protection for roofs. SPS 321.28(1)(a)(a)
All roofs shall be designed and constructed to assure drainage of water.
(2) Underlayment for shingles.
Underlayment consisting of number 15 asphalt-impregnated felt paper or equivalent or other type I material that shows no water transmission when tested in accordance with ASTM D 226 or ASTM D 4869 shall be provided under shingles.
SPS 321.28 Note
Note: Underlayment materials meeting the requirements of ASTM D 1970 meet the performance requirements of this section.
Shingles that have a self-sealing adhesive strip shall include a sealant which has an average bond strength of at least 1.5 pounds per 3.75 inches of shingle width, at 32°
SPS 321.28 Note
Note: The department will accept results of testing conducted in accordance with an approved test method for verifying compliance with the sealant uplift resistance required in this paragraph. Information on the applicable test method may be obtained from the department.
Each shingle package shall be labeled by the manufacturer to indicate conformance to the applicable ASTM standard for each type of shingle or the exception in par. (c)
Shingles shall be installed in accordance with the manufacturer's recommendations.
Shingles shall have at least 4 fasteners per strip shingle or 2 fasteners per interlocking shingle, unless the manufacturer has other specifications.
Shingle head lap shall be at least 2 inches, unless the manufacturer has other specifications.
SPS 321.28 Note
See s. SPS 320.07 (62)
for definitions of shingle terms.
SPS 321.28 Note
Section SPS 320.04 (2)
requires compliance with all parts of this code, including these roofing provisions, for an alteration to any dwelling that is regulated under this code.
Fiberglass asphalt shingles shall conform to ASTM D 3462 except that laminated shingles shall have a tear strength of at least 1450 grams in each ply.
Shingled or shake roofs that extend over a heated area of a dwelling or attached garage and that have a slope of 4:12 or less shall be provided with ice dam protection in the form of sheet metal or a product labeled as meeting the requirements of ASTM D 1970.
The ice dam protection shall extend at least 30 inches up the roof slope from the roof edge and at least 12 inches up the roof slope beyond the inner face of the exterior wall.
(5) Other roof coverings.
All roof coverings not otherwise addressed in this section shall be installed in accordance with the manufacturer's instructions or a national standard recognized by the department.
New roof coverings may not be installed over existing roof coverings where any of the following conditions exist:
The existing roof or roof covering is water-soaked or has deteriorated such that it is inadequate as a base for additional roofing.
The existing roof is wood shake, slate, clay, cement or asbestos-cement tile.
The existing roof has 2 or more applications of any type of permanent roof covering.
Flashing shall be installed at the junction of chimneys and roofs, in all valleys, and around all roof openings.
Open valleys shall be flashed with at least No. 28 gauge corrosion-resistant sheet metal, 16 inches wide, or a layer of at least 50-pound roll roofing, 16 inches wide, placed over a layer of number 15 roofing underlayment.
Flashing of closed valleys.
Where shingles are laced or woven over the valley, the valley shall be flashed with one of the following:
At least one layer of 50-pound roofing, at least 20 inches wide, over a layer of number 15 roofing underlayment.
Chimneys shall be flashed and counter-flashed to a height of at least 6 inches.
Chimney crickets or saddles shall be installed where the upper side of a chimney is more than 30 inches wide on a sloping roof.
The intersection of the cricket and the chimney shall be flashed and counter-flashed to a height of at least 6 inches.