relatept0 maximum allowable span of beams
Figure 460-12. Decking, joist, and beam span relationships.
house sill along one edge. The joists are supported by a ledger connected to the house sill and a continuous beam which in turn Is supported by three 1 200 mm (4 ft) long piers. Although the effective span is the distance from the face of beam to the face of the sill ledger, a margin of safety is achieved by using the centerline span value in calculations. Basic wood deck and boardwalk member sizing involves the following steps:
1. Preliminary Framing Plan: Develop a preliminary framing plan to locate the position of bearing beams, associated posts and piers, joists, and decking systems with the aim of creating a simple, uncluttered structural design.
2. Estimate the Design Loads: Estimate the loads to be carried by each structural element of the deck and the accumulated loads bearing down on each post or pier. Local codes require minimum load allowances for live loads (people, snow drifts, etc.) and dead loads (decking and hardware weight), which vary from region to region. (Refer to 4.3 Estimating Design Loads for calculations).
3. Calculate Lumber Dimensions: Using the appropriate span tables, determine the dimensions required for each structural element, in this case, the joists, beams, and posts The design loads exerted by each tributary load area (t) are transferred to their respective posts. Figure 460-13 illustrates the general framing plan of the proposed deck, and the dashed lines outline the center (tO and corner (t) load areas. The total tributary load area exerted on
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