Extension Costs: Timber Frame vs Brick 2026 (UK)
Timber-frame extensions cost £1,800–£2,400/m² in 2026; traditional masonry-cavity (brick) costs £2,000–£2,800/m². On a typical 30m² single-storey rear extension that is roughly £54,000–£72,000 (timber) vs £60,000–£84,000 (brick) — a 10–20% headline cost gap. But headline cost is the wrong question. Timber-frame wins on build speed (8–10 weeks vs 12–16), thermal performance (easier to hit Future Homes Standard U-values), and moisture during winter builds. Brick wins on long-term resale (surveyors still mark down some timber stock), structural alterations later, and insurance excesses. Here is the full side-by-side, costed for 2026 prices.
Side-by-side comparison
| Factor | Timber frame | Brick (masonry cavity) |
|---|---|---|
| Cost per m² (2026) | £1,800–£2,400 | £2,000–£2,800 |
| 30m² build total | £54k–£72k | £60k–£84k |
| Typical build time | 8–10 weeks | 12–16 weeks |
| U-value (wall) | 0.15–0.18 W/m²K easily | 0.18–0.22 W/m²K standard |
| Future Homes Standard compliance | Easier (factory tolerances) | Harder (needs full-fill insulation) |
| Weather-tolerance during build | Faster to dry, less rain-sensitive shell | Mortar curing delays in cold/wet weather |
| Mortgage acceptance | Mainstream lenders OK, some niche caution on "non-standard" stock | Universally accepted ("standard construction") |
| Resale value uplift | Roughly equal in many areas, lower in conservative markets | Slight premium in traditional markets (5–7% on average) |
| Future structural changes | Limited (load paths fixed at factory) | Flexible (any internal layout) |
| Acoustic performance | Good with mass-loaded panels | Excellent without modification |
Three variables that flip the answer
1. Site access
If your only access is through the house or a 1m side passage, factory-cut timber-frame panels save weeks of wheelbarrow brickwork. Brick can cost an extra 10–15% in labour on access-restricted sites.
2. Local market expectations
In areas where the housing stock is uniformly brick (much of the Midlands and South-East suburban), surveyors and buyers expect brick. Resale uplift is materially lower on a timber-frame extension in those postcodes. In Scotland and parts of the South-West where timber frame is mainstream, this concern disappears.
3. Future Homes Standard
From mid-2025 the Future Homes Standard tightened U-value requirements. Brick now typically needs full-fill insulation plus thermal blocks to comply, adding £1,500–£3,000 to a 30m² build. Timber frame meets the standard with stock panels.
FAQs
Related guides
- Compare extension materials: brick vs timber frame
- How much does a rear extension cost in 2026?
- Is a home extension worth it in 2026 UK?
- Do I need planning permission for an extension?
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