Section SPS 375.17 - Brackets(1) Brackets for a 28 inch or 30 inch platform, when spaced not more than 4 feet apart, shall be made of not less than 7/8 inch square bars or 11/2 x 11/2 x 1/4 inch angles; such bars or angles shall be larger if the platform is wider or if the brackets are farther apart. Each bracket shall be fastened at the top, to the wall, by a through bolt (at least 7/8 inch diameter), nut, and washer (at least 4 inch diameter). The slope of the lower bracket bar shall be not less then 30º with the horizontal. The lower bar shall have a washer or shoulder to give sufficient bearing against the wall. Note: In applying the requirements of the building code to the design of a bracket, the lower bracket bar must be designed according to the column formula. According to this formula (for example), brackets made of 1 inch square wrought iron, 4 feet apart, carrying a 3 feet 4 inches platform, are just within the limit of stiffness. If the brackets were over 4 feet apart, a heavier bar or an angle would have to be used.
(2) The strength of the wall to which brackets are to be attached shall be carefully considered in determining the spacing, shape, and inside connection of brackets, so that under full load the wall will not be unduly strained.Wis. Admin. Code Department of Safety and Professional Services SPS 375.17
1-2-56; renum., Register, September, 1974, No. 225, eff. 10-1-74.