This is the first edition of CSA Standard CAN3-S406-M, Construction of Preserved Wood Foundations. It is written in SI (metric) units.
Previously, the principal Canadian source of information on this subject was the Construction Guide for Preserved Wood Foundations, PWF-l, issued by the Canadian Wood Council. Although the Construction Guide has been referenced in some building codes, it was not prepared to be used as a specification or a standard, not being written in mandatory language, but only as a guide.
The purpose of CSA Standard CAN3-S406-M is to provide a standard for the construction of preserved wood foundations that can be referenced in building codes and whose requirements, written in mandatory language, can be legally enforced by regulatory authorities.
The construction requirements of this Standard are based on those of the National Building Code of Canada - 1980 (NBCC-1980) and on additional requirements set forth in CSA Standard CAN3-086-M, Code for Engineering Design in Wood.
Except for the special provisions outlined herein, the building practices should conform to those of the National Building Code of Canada and/or appropriate provincial and municipal building codes, and in all matters good building practices are assumed.
This Standard was prepared by the Technical Committee on Engineering Design in Wood under the jurisdiction of the Standards Steering Committee on Structures (Design), and was formally approved by these Committees. It has been approved as a National Standard of Canada by the Standards Council of Canada.
This Standard applies to the materials and principles of fabrication or installation of preserved wood foundations.
1.1.2 Specific Details
Specific details are provided for buildings up to 2 storeys above the foundation in building height and having a building area not exceeding 600 m2.
1.1.3 Design Assumptions
Tabular data and figures in this Standard are based upon the general principles provided in CSA Standard CAN3-086-M, Code for Engineering Design in Wood, with the following assumptions:
(a) Soil bearing capacity: 75 kN/m2 or more;
(b) Clear spans for floors: 5000 mm or less;
(c) Floor loadings:
(i) 1.9 kN/m2 for first floor and suspended floor; and
(ii) 1.4 kN/m2 for second storey floor;
(d) Foundation wall heights:
i) 2400 mm for slab floor foundation; and
(ii) 3000 mm for suspended wood floor foundation;
(e) Top of granular layer to top of suspended wood floor: 600 mm;
(f) Lateral load from soil pressure: equivalent to fluid pressure of 4.7 kN/m2 per metre of depth;
(g) Ground snow load: 3 kN/m2;
(h) Basic snow load coefficient: 0.6;
(j) Roof loads are carried to the exterior wall;
(j) Dead loads:
(j) Roof: 0.50 kN/m2;
(ii) Floor: 0.47;
(iii) Wall (with siding): 0.32;
(iv) Wall (with masonry veneer): 1.94;
(v) Foundation wall: 0.27;
(vi) Partitions: 0.20;
(k) Modification factors:
(j) Duration of load: 0.90;
(ii) Load sharing: 1.15 for bending and shear; 1.10 for compression parallel to grain;
(iii) Service condition: 0.S4 for bending; 0.69 for compression; 0.96 for shear; 0.94 for MOE.
Note: In calculating footing sizes and allowable backfill heights for foundation walls, a factor of 0.8 was used to reduce live loads from the roof and floors. This factor is intended to reflect the probability of full design loads on the roof and floors at the same time.
1.1.4 Other Conditions
For more severe conditions, preserved wood foundations shall be designed using CSA Standard CAN3-086-M, Code for Engineering Design in Wood.