How Many Roof Trusses Do I Need?
Quick Answer
Approximately 18 trusses for a 10-metre building
Based on: 600mm centres along the building length, including gable-end trusses
How We Calculated This
Trussed rafters are spaced at regular centres along the length of the building:
- Building length: 10m
- Truss spacing: 600mm centres (standard)
- Number of spaces: 10,000 ÷ 600 = 16.67, rounded up to 17 spaces
- Number of trusses: 17 + 1 = 18 trusses
Truss Spacing Options
- 600mm centres: Standard for most UK domestic roofs (concrete tiles, slates)
- 450mm centres: Heavy coverings or long spans
- 400mm centres: Some engineered truss specifications
Types of Truss
- Fink (W): Most common domestic truss — suits spans up to ~11m
- Attic truss: Provides habitable room in the roof space
- Mono truss: Single slope (lean-to extensions)
- Raised tie: Higher ceiling height in rooms below
- Gable-end truss: Infilled or ladder-frame type at gable walls
Ordering Tips
Trusses are manufactured to order — lead times are typically 3–6 weeks. You will need to provide the span, pitch, eaves detail, and any special requirements (e.g., water tank loads, room-in-roof). A structural engineer or the truss manufacturer will produce the design and layout drawings.
Last updated: April 2026. Truss design must comply with BS EN 1995 (Eurocode 5) and be carried out by a competent engineer. Quantities are estimates only.