16/10/2026
How far can a floor joist span? It depends on four things: the timber grade, the joist size, the spacing and the load. Change one and the answer changes. The same 47 × 195 joist loses 0.78 m of span going from 400 mm to 600 mm centres. HouseBuild's span tables give you the figure for every combination, so you can check before you order.
Always confirm the final design with your engineer.
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