Effective Date of Rule: April 1, 2008.
Purpose: To amend chapter 51-51 WAC, the 2006 International Residential Code, Section R403.1.6.1 to reinstate the requirement that bearing walls be anchored to the foundation in certain seismic design categories.
Citation of Existing Rules Affected by this Order: Amending WAC 51-51-0403.
Statutory Authority for Adoption: RCW 19.27.190 and 19.27.020.
Other Authority: Chapters 19.27 and 34.05 RCW.
Adopted under notice filed as WSR 07-16-109 on July 31, 2007.
Number of Sections Adopted in Order to Comply with Federal Statute: New 0, Amended 0, Repealed 0; Federal Rules or Standards: New 0, Amended 0, Repealed 0; or Recently Enacted State Statutes: New 0, Amended 0, Repealed 0.
Number of Sections Adopted at Request of a Nongovernmental Entity: New 0, Amended 1, Repealed 0.
Number of Sections Adopted on the Agency's Own Initiative: New 0, Amended 0, Repealed 0.
Number of Sections Adopted in Order to Clarify, Streamline, or Reform Agency Procedures: New 0, Amended 0, Repealed 0.
Number of Sections Adopted Using Negotiated Rule Making: New 0, Amended 0, Repealed 0; Pilot Rule Making: New 0, Amended 0, Repealed 0; or Other Alternative Rule Making: New 0, Amended 1, Repealed 0.
Date Adopted: November 9, 2007.
John P. Neff
AMENDATORY SECTION(Amending WSR 07-01-090, filed 12/19/06, effective 7/1/07)
WAC 51-51-0403 Section R403 -- Footings.
R403.1 General. All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, wood foundations, or other approved structural systems which shall be of sufficient design to accommodate all loads specified in Section R301 and to transmit the resulting loads to the supporting soil within the limitations determined from the characteristics of the soil. Footings shall be supported on undisturbed natural soil or engineered fill. Foundation walls complying with Section R404 or stem walls complying with Section R403.1.3 shall be permitted to support exterior walls, exterior braced wall lines and exterior braced wall panels provided they are supported by continuous footings.
R403.1.2 Braced Wall Panels in Seismic Design Categories D0, D1 and D2. The braced wall panels at exterior and interior walls of buildings located in Seismic Design Categories D0, D1 and D2 shall be supported by foundations.
|EXCEPTIONS:||1. In buildings in Seismic Design Categories D0 and D1, and in one-story buildings in Seismic Design Category D2, interior braced wall panels are not required to be supported by foundations, provided no building plan dimension perpendicular to the interior braced wall lines is greater than 50 feet.|
|2. In two-story buildings in Seismic Design Category D2, interior braced wall panels are not required to be supported by foundations, provided all of the following conditions are met:|
|2.1. No building plan dimension perpendicular to the interior braced wall lines exceeds 50 feet;|
|2.2. The distances between braced wall lines do not exceed twice the building width measured parallel to the braced wall lines;|
|2.3. The braced wall panels at the first story are continuously supported by floor joists, blocking or floor beams; and|
|2.4. The heights of braced wall panels in under-floor spaces do not exceed 48 inches (1219 mm).|
|EXCEPTIONS:||1. In under-floor spaces, cripple walls shall be permitted to substitute for masonry or concrete foundation walls provided they comply with the following:|
|a. They are located directly below the interior braced wall panels above;|
|b. They are braced in accordance with Sections R602.10.2 and R602.10.11.4 for cripple wall bracing; and|
|c. They are supported by footings complying with Sections R402 and R403, except that the footing of a foundation supporting an interior braced wall panel is not required to be continuous.|
|2. Footings of foundations supporting interior braced wall panels are not required to be continuous but shall be constructed beyond the ends of foundation walls, stem walls and cripple walls supporting braced wall panels for a minimum distance of 4 inches and a maximum distance of the footing thickness. The footing extension is not required at intersections with other footings.|
Where a construction joint is created between a concrete footing and a concrete stem wall, minimum vertical reinforcement of one No. 4 bar shall be provided at not more than 4 feet (1219 mm) on center. The bars shall extend to 3 inches (76 mm) clear of the bottom of the footing, have a standard hook, and extend into the stem wall the lesser of 2 inches (49 mm) clear of the top of the wall and 14 inches (357 mm).
Where a solidly grouted masonry stem wall is supported on a concrete footing, minimum vertical reinforcement of one No. 4 bar shall be provided at not more than 4 feet (1219 mm) on center. The bars shall extend to 3 inches (76 mm) clear of the bottom of the footing, have a standard hook, and extend into the stem wall to 2 inches (49 mm) clear of the top of the wall.
Masonry stem walls without solid grout and vertical reinforcing are not permitted.
Concrete and masonry stem walls shall comply with the requirements of Section R404 for foundation walls.
|EXCEPTION:||In detached one- and two-family dwellings of light-framed construction and three stories or less above grade, plain concrete footings supporting walls, columns or pedestals are permitted.|
R403.1.4 Minimum depth. All exterior footings shall be placed at least 12 inches (305 mm) below the undisturbed ground surface. Where applicable, the depth of footings shall also comply with Sections R403.1.4.1 through R403.1.4.2.
R403.1.4.1 Frost protection. Except where otherwise protected from frost, foundation walls, piers and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:
1. Extend below the frost line specified in Table R301.2(1);
2. Construct in accordance with Section R403.3;
3. Construct in accordance with ASCE 32; or
4. Erect on solid rock.
|EXCEPTIONS:||1. Protection of freestanding accessory structures with an area of 600 square feet (56 m2) or less and an eave height of 10 feet (3048 mm) or less shall not be required.|
|2. Protection of freestanding accessory structures with an area of 400 square feet (37 m2) or less, of other than light-framed construction, with an eave height of 10 feet (3048 mm) or less shall not be required.|
|3. Decks not supported by a dwelling need not be provided with footings that extend below the frost line.|
R403.1.6 Anchorage at braced wall panels. Where braced wall panels are supported by monolithic slabs, footings or foundations, the wood sole plates, wood sill plates or cold-formed steel bottom tracks shall be anchored to the slab cast monolithically with a footing, footing or foundation in accordance with ((
this)) Section R403.1.6.
The wood sole or sill plate shall be anchored to the monolithic slab, footing or foundation with anchor bolts spaced a maximum of 6 feet (1829 mm) on center. There shall be a minimum of two bolts per plate section with one bolt located not more than 12 inches (305 mm) and not less than seven bolt diameters from each end of the plate section. Bolts shall be at least 1/2 inch (13 mm) in diameter and shall extend a minimum of 7 inches (178 mm) into masonry or concrete. A nut and washer shall be tightened to a snug-tight condition on each bolt to the plate.
Cold-formed steel framing systems shall be fastened to wood sill plates or anchored directly to the foundation in accordance with Section R505.3.1 or R603.3.1.
|EXCEPTIONS:||1. Foundation anchorage, spaced as required to provide equivalent anchorage to 1/2-inch-diameter (13 mm) anchor bolts.|
|2. Walls 24 inches (610 mm) in total length or shorter connecting offset braced wall panels shall be anchored to the footing or foundation with a minimum of one anchor bolt located in the center third of the plate section and shall be attached to adjacent braced wall panels as specified in Figure R602.10.5 at the corners.|
|3. Walls 12 inches (305 mm) in total length or shorter connecting offset braced wall panels shall be permitted to be connected to the footing or foundation without anchor bolts. The wall shall be attached to adjacent braced wall panels as specified in Figure R602.10.5 at the corners.|
1. Bearing walls and interior braced wall sill plates shall be anchored to footings or foundations with anchor bolts spaced at not more than 6 feet (1829 mm) on center and located within 12 inches (305 mm) from the ends of each plate section when supported on a continuous foundation.
2. The maximum anchor bolt spacing shall be 4 feet (1219 mm) for buildings over two stories in height.
3. Plate washers complying with Section R602.11.1 shall be provided for all anchor bolts over the full length of required braced wall lines. Properly sized cut washers shall be permitted for anchor bolts in wall lines not containing braced wall panels or in braced wall lines.
4. Stepped cripple walls shall conform to Section R602.11.3.
5. Where wood foundations in accordance with Sections R402.1 and R404.2 are used, the force transfer shall have a capacity equal to or greater than the connections required by Section R602.11.1 or the braced wall panel shall be connected to the wood foundations in accordance with the braced wall panel-to-floor fastening requirements of Table 602.3(1).
[Statutory Authority: RCW 19.27.074, 19.27.020, and chapters 19.27 and 34.05 RCW. 07-01-090, § 51-51-0403, filed 12/19/06, effective 7/1/07.]