Diagram — what is being calculated
01 / Inputs
Enter your actual clear span to check adequacy. Leave blank to view max spans only.
Continuous spans: Joists continuous over two or more spans may use a 10% increase per NZS 3604:2011 Table 7.1 Note 1 — but only where each adjacent span is between 80% and 125% of the span being checked. If spans differ more than that, treat each as a single span.
02 / Result
Enter inputs to find maximum span
All joist sizes at entered spacing
| Size (depth×thickness) | Spacing (mm) | Max Span | Adequate? |
|---|
NZS 3604:2011 — scope and limitations. Applies to solid timber joists in timber-framed buildings within NZS 3604 scope (residential, ≤ two storeys, ≤ 10 m wall height, good ground). 2.0 kPa table values are from NZS 3604:2011 Table A7.1. For spans exceeding standard tables, consider LVL or engineered joists (use manufacturer span tables). All results must be verified by a Chartered Professional Engineer or Licensed Building Practitioner before use in construction.
NZS 3604:2011 Table 7.1 — Floor Joist Maximum Clear Span (m) @ 1.5 kPa, Dry in Service
Single span. For continuous spans add 10%. Source: NZS 3604:2011 Table 7.1.
| Size (mm) | @ 400c | @ 450c | @ 600c |
|---|---|---|---|
| 90×45 | 1.45 / 1.55 | 1.40 / 1.50 | 1.30 / 1.40 |
| 140×45 | 2.70 / 2.90 | 2.60 / 2.80 | 2.00 / 2.15 |
| 190×45 | 3.55 / 3.80 | 3.45 / 3.70 | 3.15 / 3.35 |
| 240×45 | 4.40 / 4.70 | 4.30 / 4.60 | 3.90 / 4.20 |
| 290×45 | 5.10 / 5.45 | 5.00 / 5.30 | 4.50 / 4.80 |
Values shown as SG8 / SG10. Table 7.1 applies to all wind zones.
NZS 3604:2011 Table A7.1 — Floor Joist Maximum Clear Span (m) @ 2.0 kPa, Dry in Service
Single span. For continuous spans add 10%. Source: NZS 3604:2011 Table A7.1.
| Size (mm) | @ 400c | @ 450c | @ 600c |
|---|---|---|---|
| 90×45 | 1.35 / 1.45 | 1.30 / 1.40 | 1.20 / 1.30 |
| 140×45 | 2.50 / 2.70 | 2.40 / 2.60 | 1.90 / 2.05 |
| 190×45 | 3.35 / 3.55 | 3.25 / 3.45 | 2.95 / 3.15 |
| 240×45 | 4.15 / 4.40 | 4.00 / 4.30 | 3.65 / 3.90 |
| 290×45 | 4.80 / 5.10 | 4.65 / 5.00 | 4.25 / 4.55 |
Values shown as SG8 / SG10. Table A7.1 applies to all wind zones.