Section 246-359-180 - Concrete footings and foundations for wood framed construction(1) Concrete used for footings and foundations must have a minimum compressive strength of two thousand pounds per square inch (psi). Concrete must be mixed and delivered in accordance with the requirements of ASTM C94 (Ready-Mix Concrete), or may be field mixed. Field mixed concrete will be subject to independent compressive strength testing and special inspection.(2) Concrete footings must be placed on firm, undisturbed soil.(3)Concrete footings must be continuous, be a minimum of twelve inches wide by six inches thick, be reinforced with a minimum of two No. 4 continuous rebar, and be at least eighteen inches below finished grade measured from the bottom of the footing.(4) Concrete foundations must be a minimum of six inches thick, be reinforced with a minimum of one continuous horizontal No. 4 rebar within twelve inches from the top, and one continuous horizontal No. 4 rebar near mid-height, be reinforced vertically with No. 4 at forty-eight inches on center, extend at least six inches above the finished grade, and have a total height of not greater than forty-eight inches.(5) Concrete foundation stem walls that are formed by a thickened concrete slab edge as part of a slab on grade floor must be reinforced with one piece of No. 4 rebar in the upper part and one piece of No. 4 rebar in the lower part of the foundation. The concrete floor will be reinforced according to WAC 246-359-430. The thickened concrete slab edge must extend at least eighteen inches below finished grade, be at least twelve inches in width, and provide a slab height of at least six inches above finished grade.(6)Where the walls are of wood construction, the treated foundation plates or sills must be bolted to the foundation or foundation wall with not less than one-half inch nominal diameter steel bolts embedded at least seven inches into the concrete and spaced not more than seventy-two inches apart. There must be a minimum of two bolts per piece with one bolt located within twelve inches of each end of each piece. A properly sized nut and washer must be tightened on each bolt to secure the place.Wash. Admin. Code § 246-359-180
Amended by WSR 15-13-091, Filed 6/15/2015, effective see belowStatutory Authority: RCW 70.114A.081. 99-03-065, § 246-359-180, filed 1/18/99, effective 2/18/99.