Construction of Preserved Wood Foundations
This is the second edition of CSA Standard CAN/CSA-S406, Construction of Preserved Wood Foundations. It supersedes the first edition, CAN3-S406, published in 1983.
This second edition has been completely reorganized such that the clause numbering follows the normal construction sequence, from site preparation, through construction of the foundation and floor systems, to backfilling and site grading.
The tabulated framing and plywood sheathing requirements have been recalculated based on the latest edition of CSA Standard CAN/CSA-086.1, Engineering Design in Wood (Limit States Design). The stud tables have been expanded to cover three lengths of stud and assumptions for supported floor systems up to 8 m in span. The coverage for size of window openings is increased, and racking due to unbalanced soil loads is addressed. Provisions have been added to address the use of floor trusses and wood sleeper floors. This edition specifies the use of hot-dipped galvanized or stainless steel nails in a treated wood materials. A table has been added to describe the qualities of native soils when used as backfill material. In general, provisions have been added or modified as appropriate to emphasize the need for installation in full conformance to the design and with the Standard.
This Standard was prepared by the CSA Technical Committee on Construction of Preserved Wood Foundations under the jurisdiction to the Standards Steering Committee on Structures (Design) and was formally approved by these Committees. It was approved by the Standards Council of Canada as a National Standard of Canada.
This Standard applies to the selection of materials for, and the fabrication and installation of, preserved wood foundations.
Specific details are provided for buildings up to two storeys in building height above the foundation and having a building area not exceeding 600 m².
This Standard provides for the optional use of wood sleeper, poured concrete slab, and suspended wood basement floor systems as components of the preserved wood foundation, and for the use of preserved wood foundations enclosing crawl spaces (see Figures A1 and A6).
The values given in SI (metric) units are the standard. The values given in parentheses are for information only.
Note: In commercial practice, nails are commonly identified by their length in inches. Lumber sizes are expressed in terms of thickness x width, with metric values (mm x mm) referring to standard dry dressed sizes and with imperial values (in x in) referring to nominal nondressed sizes, both in conformance to CSA Standard CAN/CSA-O141, Softwood Lumber.