How many roof trusses do I need?

The number of trusses is calculated as: (Roof length / 0.6m spacing) + 1, plus gable trusses. For example, a 10m long roof needs (10 / 0.6) + 1 = 17.67, rounded up to 18 standard trusses, plus 2 gable trusses = 20 trusses total. Standard UK spacing is 600mm (2 feet) on centre.

What is the standard truss spacing in the UK?

The standard spacing for domestic roof trusses in the UK is 600mm (approximately 2 feet) centre to centre. This spacing works with standard plasterboard sheets (1200mm wide, supported on every other truss) and standard insulation rolls. Some designs may require 400mm spacing for heavier tile loads or longer spans.

What is a gable truss?

A gable truss (also called a gable ladder or gable frame) sits at each gable end of the roof. It has a different design to standard trusses — usually a simplified frame with vertical studs instead of internal web members, designed to support the gable wall cladding and verge overhang. They are essential for a proper gable end finish.

What is the maximum span for a Fink truss?

Standard Fink (W) trusses can span up to about 11 metres for domestic loading in the UK. For wider spans, the truss design may need to be modified with additional web members, or an attic truss or steel beam may be more appropriate. All trusses should be designed and certified by a structural engineer or truss manufacturer to comply with BS 5268 or Eurocode 5.

How much do roof trusses cost in the UK?

Roof truss prices vary significantly depending on the span, type and complexity. As a rough guide: standard Fink trusses for a 6-8m span typically cost £50-£100 each. Attic/room-in-roof trusses cost £150-£350 each due to their heavier construction. Prices also depend on delivery distance from the manufacturer. Always get a specific quote from a truss fabricator. For the rest of your roofing materials, use our Roof Tile Calculator and Felt and Batten Calculator.

Roof Truss Calculator — How Many Trusses Do I Need?

Roof Truss Calculator — Quantities & Spacing

Calculate how many roof trusses you need based on building span and roof length. Standard 600mm centres for UK construction.

Building Span

Width of building (wall to wall)

Roof Length

Length of building along the ridge

Truss Type

Include gable trusses

Adds 2 gable trusses (one per end)

Price Per Truss (optional)

Enter your supplier quote per truss

How We Calculate This

Our roof truss calculator determines the number of trusses needed based on your roof length and the standard 600mm spacing used in UK domestic construction. It also accounts for gable trusses at each end.

The formula

Standard trusses = (Roof length ÷ 0.6m) + 1
Gable trusses = 2 (one at each end)
Total = Standard trusses + Gable trusses

The +1 accounts for the truss at the starting position. For mono-pitch roofs, only one gable truss is typically needed.

Truss types

Fink (W): Most common domestic truss, suitable for spans up to ~11m. Internal W-shaped web members.
Attic / Room-in-Roof: Designed to create usable space in the loft. Heavier and more expensive.
Mono-Pitch: Single slope, used for lean-to extensions, porches and garages.
Raised Tie: Bottom chord raised to give more headroom in the loft space, useful for storage.

Important notes

All trusses must be designed by a qualified truss manufacturer or structural engineer. They are made to order based on your specific span, pitch, loading (tile type, snow load, wind load) and any special requirements. This calculator gives an estimate of quantities only — always confirm with your truss supplier.

Frequently Asked Questions

Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Roof Truss Calculator — Quantities & Spacing

How We Calculate This

The formula

Truss types

Important notes

Frequently Asked Questions

Related Calculators

Roof Tile Calculator

Ridge Tile Calculator

Felt and Batten Calculator

Soffit and Fascia Calculator

Gutter Sizing Calculator