Diagram — what is being calculated
01 / Select Scenario
02 / Joist Dimensions
For continuous joists, enter the span on the other side of this support. LD will use whichever is longer.
NZS 3604 cl. 1.3: The loaded dimension is the horizontal plan distance from the member centreline to the nearest parallel load-bearing line. For joists, it is half the joist clear span (or half the maximum joist span where continuous). Use the result directly in span table lookups.
03 / Result
Select a scenario and enter dimensions
NZS 3604:2011 Clause 1.3. The loaded dimension is the plan horizontal distance from the member's centreline to the nearest parallel load-bearing line. This value is used directly in all NZS 3604 span table lookups. The definition applies to joists, bearers, purlins, rafters, and lintels.
Quick Reference — Loaded Dimension Formulae
| Member | Loaded Dimension | Notes |
|---|---|---|
| Floor joists → bearer | ½ × joist clear span | Continuous: use ½ × longest adjacent span |
| Bearers → wall or pile | ½ × bearer clear span | Continuous: use ½ × longest adjacent span |
| Lintel in long wall (rafters span across) | ½ × rafter span | Each long wall takes half the roof load |
| Lintel in gable end (rafters parallel) | ½ × rafter run | LW = half the distance ridge to outer wall |
| Purlins | Plan distance to nearest support | Refer to purlin span tables |