Monday, December 9, 2013


Example in the Use of Approved Documents

Problem:- the sizing of suspended upper floor joists to be spaced at 400mm centres with a clear span of 3600m for use in a two storey domestic dwelling.

Building Regulation A1:- states that the building shall be constructed so that the combined dead, imposed and wind loads are sustained and transmitted by it to the ground †

(a) safely, and
(b) without causing such deflection or deformation of any part of the building, or such movement of the ground, as will impair the stability of any part of another building.

Approved Document A:- guidance on sizing floor joists can be found in `Span Tables for Solid Timber Members in Dwellings', published by the Timber Research And Development Association (TRADA), and BS5268-2: Structural use of timber. Code of practice for permissible stress design, materials and workmanship.

Dead loading is therefore in the 0.25 to 0.50kN/m2 band From table on page 633 suitable joist sizes are:- 38 X 200, 50 X 175, 63 X 175 and 75 X 150.

Final choice of section to be used will depend upon cost; availability; practical considerations and/or personal preference.

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