Estimate preliminary FLW
This is a plain estimator for understanding FLW. Complex layouts, cantilevers, point loads, stairs, roof loads and concentrated loads need separate review.
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What Is Floor Load Width?
Floor load width is one of the key inputs for deck bearer span tables. This guide explains FLW in plain English and links to the FLW calculator.
FLWExplains floor load width, bearer FLW and span-table column selection.
Estimated floor load width
1200 mm
For an edge bearer, preliminary FLW is half the joist span loading from one side.
Use this to understand the term only. Always check the original bearer span table and project-specific requirements.
FLW rules of thumb
- Edge bearers often carry load from one side of the deck.
- Internal bearers can carry load from joists on both sides.
- Bearer tables commonly list FLW columns such as 900, 1200, 1800, 2400 or 3000 mm.
- Using a larger available FLW column is usually more conservative than using a smaller one.
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Floor load width FAQs
What is floor load width?
Floor load width is the width of deck or floor area that contributes load to a bearer or beam.
Is FLW the same as joist span?
Not always. For a simple internal bearer carrying joists from both sides, FLW may relate to half the joist span on each side. For an edge bearer it may relate to one side only.
How do I calculate FLW for a deck bearer?
For preliminary estimating, add the tributary joist length feeding into each side of the bearer. Edge bearers usually carry one side. Internal bearers may carry load from both sides.
Why does a larger FLW reduce span?
A larger floor load width means the bearer carries load from a wider strip of deck, so the allowable span generally reduces.
Should I round FLW up?
For preliminary comparisons, rounding up to the next available published FLW column can be conservative, but final design must follow the source table rules.