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AFBPA� /� AMERICAN FOREST £� PAPER ASSOCIATION � American Wood Council °' Engineered and Traditional Wood Products Design Requirements for the Permanent Wood Foundation System Prepared for the State of Minnesota by the American Forest& Paper Association Introduction The Permanent W ood Foundation(PWF)system uses pressure preservative-treated dimension lumber and plywood,constructed similarly to wood frame walls,as a building foundation. Foundation walls transfer the weight of the structure,via concrete,gravel or crushed stone footings,to suitable bearing conditions. In addition to transferring vertical loads,the walls of the foundation also resist horizontal forces resulting from backfill. Therefore, the structural elements of a foundation wall are under compression and bending loads, simultaneously. Dimension lumber(e.g. 2x6, 2x8), when sheathed with plywood,provides an ideal structural system for resisting these forces. When properly designed for the appropriate loads and detailed to prohibit water intrusion, the PWF provides a structurally sound foundation system. PWF Acceptance The PWF system is recognized by all U.S.model building codes and the U.S.Department of Housing and Urban Development. The American Forest & Paper Association (AF&PA) is the publisher of TechnicalReport#7,BasicRequirementsfor thePermanent WoodFoundation System-1987(TR7) with 1992 revisions, the building-code-recognized reference for the design and construction requirements of the PWF. This document provides detailed information on design load criteria, treated lumber and plywood requirements, fastener durability, waterproofing materials, and footing design. The publication does not provide prescriptive solutions for the appropriate size, grade, or species of lumber or plywood. The loads induced on foundation walls are unique and may result in a required analysis of the resisting system. With one exception presented later in this paper, it is the position of AF&PA that foundations must be designed for each unique building configuration and soil condition. The State ofMinnesota's buildingcode has adopted the 1997 Uniform Building Code(UBC). Chapter 18,Division II of the 1997 UBC is based on TR7. Therefore,any jurisdiction enacting the Minnesota State Building Code must follow the provisions of this section in the design, construction, and fabrication of wood foundations. Further, any jurisdiction enacting the Minnesota State Building Code has the option of referencing Appendix Chapter 3, Division III, of the UBC. This appendix 1 1 1 1 Nineteenth Street, NW,Suite 800 Washington,DC 20036 202 463-2766 Fax: 202 463-2791 www.awc.org America's Forest �r Paper People S"^—Improving Tomorrow's Environment Today'n