Is timber frame cheaper than blockwork?

Cost-neutral or slightly more expensive on a single-storey extension once brick veneer is added. The cost advantage emerges on two-storey, large-span or difficult-access projects where speed and structural lightness reduce programme cost and foundation cost.

Will my insurance accept a timber frame extension?

Yes — modern timber frame to NHBC and BBA standards is fully insurable. Notify your insurer at the design stage. Some legacy insurers add a small premium but most price equivalent to masonry.

How does timber frame perform thermally?

Excellent — typical wall U=0.16 with 140mm + 50mm insulated panel; can go to U=0.11 with 215mm deep wall for Passivhaus. Airtightness 1–3 m³/h/m² with proper detailing. Internal services voids prevent puncturing the vapour control layer.

Does Builderr build timber frame?

Yes — we work with closed-panel suppliers Frame Homes, TJL Group, Beattie Passive and Kingspan TEK timber. Design coordinated with our structural engineer at architectural stage; crane logistics handled by us.

Timber Frame Extension Cost London 2026 | Builderr

How Much Does a Timber Frame Extension Cost in London?

A timber frame extension in London costs £2,200–£3,500 per m² turnkey, comparable to blockwork on capital cost but 20–30% faster to weatherproof. Best for: difficult-access sites, sites with poor ground (lighter than masonry), large open spans, and Passivhaus targets. Brick veneer outer skin £80–£140 per m² for conservation area match.

Timber frame construction types

Open panel: factory-prefabricated wall panels with studwork and OSB sheathing — insulation, vapour control and plasterboard added on site. Lower factory cost, more site labour. Closed panel: factory-finished panels with insulation, vapour control, services voids and (sometimes) windows pre-installed. Higher factory cost, faster site programme — a typical single-storey extension goes up in 3–5 days. Engineered timber: I-joists, glulam beams, CLT (cross-laminated timber) for large spans and exposed structural finishes. CLT becoming popular for large open-plan rear extensions where the timber soffit is the architectural feature.

Cost breakdown

Open panel kit (walls + roof structure for 25m² single-storey): £8,000–£14,000 supply only. Closed panel kit: £14,000–£22,000 supply only. Install labour: £4,000–£8,000 (3–5 days closed panel, 5–8 days open panel). Brick veneer or render outer skin: £80–£140 per m² for brick, £40–£80 per m² for render — needed in most London conservation areas. Foundation: timber frame is 30–40% lighter than blockwork, foundations can be reduced — save £800–£2,500. Finishes (plasterboard, plaster, screed, M&E): same as any construction. Total turnkey single-storey 25m² extension with timber frame: £55,000–£90,000 (£2,200–£3,500 per m²).

When timber frame wins

Difficult access (rear garden only, narrow side access): panels craned over the existing house in 1 day vs months of brick deliveries. Poor ground: timber frame's reduced foundation load avoids piling on some sites. Large spans: glulam or LVL beams span 6–9m without intermediate supports — ideal for open-plan kitchen extensions. Speed: closed-panel timber frame extension goes from foundation complete to weathertight in under a week. Sustainability: embodied carbon roughly 50% of equivalent masonry. Passivhaus and EnerPHit: timber frame with deep cavity insulation and exterior wrap is the most cost-effective Passivhaus wall system in London. Conservation areas: brick veneer outer skin matches London stock brick context.