Technical Booklet D Structure·Page 30·4B.11
Joist section sizes and processing standards
Floor joist section sizes must be sawn and processed according to specified tolerances (BS EN 336 tolerance classes 1 and 2) or Canadian/American Lumber Standards (CLS/ALS) processed sizes to provide level surfaces.
The section sizes are either sawn across the timber thickness in accordance with tolerance class 1 of BS EN 336 and processed in accordance with tolerance class 2 of BS EN 336 across the timber width (joist depth), or are Canadian Lumber Standards/ American Lumber Standards (CLS/ALS) processed sizes in accordance with tolerance class 2, to provide level surfaces for ease of ceiling lining and the fixing of structural decking.
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