Diagram — what is being calculated
01 / Inputs
Distance from lintel to ridge / roof structure supported, measured on plan.
How to measure load width: Load width is the horizontal distance on plan from the lintel centreline to the nearest parallel load-bearing line (ridge, load-bearing wall, or support). For a gable roof: LW = half the roof width. For a lean-to: LW = full lean-to width.
02 / Result
Enter inputs and find lintel size
Available lintel options for this span & load combination
| Size (depth×thickness) | Make-up | Max Span @ entered LW | Adequate? |
|---|
NZS 3604:2011 — scope and limitations. Spans are interpolated from NZS 3604:2011 Table 8.9 (roof only) for solid timber lintels in timber-framed buildings within the standard's scope (residential and similar buildings up to two storeys, ≤10 m wall height). Note: The load-factor adjustments applied here for roof + floor and roof + two floors are conservative approximations — NZS 3604 provides separate span tables (Tables 8.10 and 8.12) for each load scenario rather than multipliers on Table 8.9. Results may be 10–20% more conservative than the actual standard tables; always verify against Tables 8.10 and 8.12 directly for lower-storey lintels. LVL values are indicative — always use the manufacturer's span tables. Steel lintels and buildings outside NZS 3604 scope require engineering design. All results must be verified by a Chartered Professional Engineer or Licensed Building Practitioner before use in construction.
NZS 3604:2011 Table 8.9 — Roof Load Only, SG8, Light Roof
Maximum clear span (mm) by load width. Sizes expressed as depth × thickness. 90mm thick = 2/45mm nailed members.
| Size (mm) | Make-up | LW 2m | LW 3m | LW 4m | LW 6m |
|---|---|---|---|---|---|
| 90×70 | Single 70mm | 1200 | 1100 | 1000 | 800 |
| 90×90 | 2/45×90 | 1400 | 1200 | 1100 | 1000 |
| 140×70 | Single 70mm | 2000 | 1700 | 1500 | 1300 |
| 140×90 | 2/45×140 | 2100 | 1900 | 1800 | 1600 |
| 190×70 | Single 70mm | 2700 | 2400 | 2100 | 1800 |
| 190×90 | 2/45×190 | 2900 | 2600 | 2400 | 2100 |
| 240×70 | Single 70mm | 3400 | 3000 | 2700 | 2200 |
| 240×90 | 2/45×240 | 3600 | 3300 | 3100 | 2700 |
| 290×70 | Single 70mm | 4000 | 3700 | 3200 | 2700 |
| 290×90 | 2/45×290 | 4200 | 3900 | 3700 | 3300 |
Source: NZS 3604:2011 Table 8.9. Applies to all wind zones. Heavy roof spans are approximately 15–25% less.
External References
Northpine SG8/SG10 Span Tables 2023 — PDF
Full NZS 3604:2011 span tables for SG8 and SG10 timber including lintels, beams, rafters and joists
BRANZ Lintels and Beams Calculator
BRANZ online tool for lintel and beam sizing under NZS 3604
MBIE — Using NZS 3604
Building.govt.nz guidance on scope and application of NZS 3604:2011