Prefabricated timber roof trusses are the standard method for constructing pitched roofs on new-build domestic properties and extensions in the UK. They are manufactured off-site to a structural design, delivered to site, and lifted into place — typically in a single day for a standard house. In 2026, truss supply alone costs £30–£60 per truss; a fully installed truss roof with ridge, bracing, felt, and battens (but not tiles) on a three-bedroom semi typically costs £5,000–£10,000.
This guide covers supply costs, installation costs, truss types, and when a cut (traditional) roof might be preferable.
What Is a Roof Truss?
A roof truss is a prefabricated engineered timber frame that spans from wall plate to wall plate, forming the structural skeleton of a pitched roof. Each truss is designed by a structural engineer to carry the required dead loads (tiles, felt, battens), imposed loads (snow), and wind loads specific to the site location and roof geometry.
The most common UK domestic truss is the fink truss (also called a W-truss) — a simple triangular form with internal web members forming a W or V pattern. Other types:
- Howe truss — internal diagonals run in the opposite direction; used for longer spans
- Attic truss (room-in-roof truss) — creates a habitable room within the roof space; much larger section members
- Mono truss — single-slope for lean-to roofs or extensions
- Hip truss — used at the hip ends of a hipped roof in combination with standard trusses
- Girder truss — multiple trusses fastened together to carry concentrated loads (dormer openings, chimney stacks)
Truss Supply Cost (2026)
Prices are per truss, delivered to site. These are supply-only prices from a UK roof truss manufacturer:
| Truss Type | Span | Pitch | Supply Price (Each) |
|---|---|---|---|
| Fink / W-truss | 5–7 m | 35–42° | £35–£55 |
| Fink / W-truss | 7–10 m | 35° | £50–£80 |
| Attic truss (2.4 m ceiling) | 6–8 m | 40° | £180–£320 |
| Mono truss (lean-to) | 3–5 m | 10–20° | £30–£55 |
| Hip truss (set per hip end) | Various | Various | £150–£350 per set |
| Girder truss (laminated) | 5–7 m | 35° | £120–£220 |
A typical 3-bed semi needs 16–22 standard fink trusses plus 2 gable trusses and ancillary bracing timber, so supply-only for the truss set alone: £600–£1,400.
Installation Cost
Truss installation requires a team (typically carpenter + 1–2 labourers), a crane or Mewp for larger roofs, and a scaffold platform at wall-plate level.
| Element | Typical Cost |
|---|---|
| Truss supply (16–22 fink, 3-bed semi) | £600–£1,200 |
| Wall plate (C24 timber, galvanised straps) | £300–£600 |
| Ridge board, purlins, bracing | £400–£800 |
| Crane hire (if needed, half day) | £500–£800 |
| Carpenter labour (2 days, 2 men) | £900–£1,500 |
| Felt and batten | £800–£1,800 |
| Scaffold (if not already in place) | £800–£2,000 |
| Total (excl. tiling) | £4,300–£8,700 |
For a larger or more complex roof (hipped ends, dormers, valley), add 30–60%. A hipped roof on a 4-bed detached: £8,000–£14,000 for the full roof structure and felt/batten stage.
Truss Roof vs. Cut Roof
Traditional cut (stick-built) roofs are assembled on site from individual rafters, purlins, and collars. They were standard before the widespread adoption of prefabricated trusses in the 1960s–1970s.
| Factor | Truss Roof | Cut Roof |
|---|---|---|
| Cost | Lower | Higher (more skilled labour) |
| Speed | Faster (1–2 days) | Slower (4–8 days) |
| Loft use | Limited (web members obstruct) | Open loft space |
| Future conversion | Requires attic trusses or reframe | Easier |
| Structural design | Off-site engineer-designed | Site carpenter + SE calcs |
| Common use | New build, extensions | Period renovation, loft conversion prep |
If you plan to convert the loft within the next 10–15 years, specify attic trusses or a cut roof from the outset — retrofitting is expensive.
Attic Trusses (Room-in-Roof)
Attic trusses create a habitable room within the roof space without the need for dormer windows. They are designed with a central clear span (typically 2.4–2.7 m wide) for a room, with structural knee walls at the eaves.
An attic truss roof on a 3-bed semi (using 10–14 attic trusses) costs significantly more:
| Element | Cost |
|---|---|
| Attic truss supply (12 trusses, 7 m span) | £2,400–£3,800 |
| Installation (additional complexity) | £2,500–£5,000 |
| Floor cassette or joists | £800–£1,800 |
| Felt and batten | £800–£1,800 |
| Total (excl. tiling, insulation, staircase) | £6,500–£12,400 |
Building Regulations are required for any new roof — Part A (structure), Part L (thermal) for new roofs where U-value must meet 0.16 W/m²K. New roofs are not exempt from Part B fire-stopping requirements at eaves and gable junctions.
Key Specifications and Standards
- Timber grade — C24 is standard for truss rafters and webs; C16 is sometimes used for ceiling tie members in lighter-loaded spans.
- Metal plate fasteners — gang-nail plates (toothed metal connector plates) pressed hydraulically at manufacture; comply with BS EN 14250.
- Fixing to wall plate — truss clips (galvanised steel straps fixed to wall plate and nailed to truss) are mandatory to resist wind uplift; spacing and type per the structural design.
- Bracing — longitudinal diagonal bracing per BS 5268 or Eurocode 5 is essential for racking resistance; often omitted on site leading to structural instability. Your structural design should specify bracing layout.
Always use a truss manufacturer who provides a structural engineer’s certificate for each truss set — most established UK manufacturers offer this as standard.
