Quick Answer
Standard Australian roof truss spacing is 600mm or 900mm centres for tile roofs and 600-1200mm for metal roofs per AS 1684. For a 12m long roof at 600mm spacing, you need 21 trusses. Always check wind region (N1-C4) and snow loads for engineered truss design.
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Australian Truss Spacing by Roof Type
| Roof Cladding | Truss Spacing | Batten Spacing |
|---|---|---|
| Concrete tile | 600mm c/c | 330mm gauge (max) |
| Terracotta tile | 600mm c/c | 300-345mm gauge |
| Colorbond / metal | 900-1200mm c/c | 900mm c/c (typical) |
| Slate | 600mm c/c | 240-280mm (smaller slates) |
Wind Region Considerations
Australian wind regions per AS 1170.2 affect truss design:
- N1, N2 (most of southern AU): Standard residential trusses, 600-900mm spacing
- N3, N4 (Adelaide hills, parts of WA): Tighter tie-down required
- C1-C4 (cyclonic — Cairns, Darwin, NW WA): Triple grip plates, 600mm spacing maximum, full engineering certification
FAQs
What is the standard roof truss spacing in Australia?
600mm centres for tile roofs, 900-1200mm for metal sheet roofs. Always per the truss manufacturer’s engineering certificate.
How many trusses do I need for a 12m long roof?
At 600mm centres: 21 trusses (including both ends). At 900mm centres: 14 trusses.
Can I increase truss spacing to save cost?
Only if the engineer redesigns the trusses for the new spacing. Wider spacing requires deeper top chord and stronger battens. Sometimes the saving on truss count is offset by the larger sections.
What is the minimum truss spacing for tiles?
Concrete tiles typically need 600mm maximum spacing because the batten gauge of 330mm is fixed by the tile size. Terracotta is similar.