Is a Home Extension Cheaper in 2026 With CLT Timber?
Usually not on the headline structure price: cross-laminated timber (CLT) panels typically cost 10–20% more than an equivalent blockwork shell in 2026. But CLT structures go up in days rather than weeks, the lighter frame can shrink foundation costs, and exposed timber can double as the finished surface — so on the right project the whole-build gap narrows to low single digits, and occasionally flips. Here's the honest 2026 comparison.
CLT extension cost — quick answer
- Structure cost: CLT typically 10–20% above an equivalent blockwork shell
- All-in 2026 rate: roughly £2,400–£3,100/m² vs £2,200–£2,800/m² for masonry
- Speed: panels erected in 2–5 days; whole build often 3–5 weeks shorter
- Hidden savings: lighter foundations, shorter prelims, exposed-timber finishes
- Best fit: awkward access, first-floor additions, design-led schemes
- Budget pick: straightforward ground-floor box? Blockwork still wins on price
Judge the whole project, not the panel quote. CLT loses on materials and wins on programme — the faster, drier build is where the money comes back. Get both systems priced against the same drawings before deciding.
CLT vs other extension build systems, 2026 UK
Indicative all-in rates for a typical 20m² single-storey rear extension, fitted and VAT-inclusive.
Where CLT costs more — and where it claws it back
CLT is a precision product: panels are CNC-cut offsite (most UK supply is still imported from Austria and Scandinavia) and craned or hand-balled into place. That supply chain is what drives the 10–20% structure premium over blockwork, and small domestic orders carry proportionally higher design and delivery overheads.
The payback is programme and simplicity. A CLT shell stands in 2–5 days, weathertight almost immediately — no wet trades, no curing time, and follow-on trades start weeks earlier. The panels weigh a fraction of masonry, which on poor ground can mean smaller foundations, and where the budget allows a visual-grade finish, exposed timber walls and soffits can delete plasterboard and decoration from whole rooms. On a straightforward ground-floor box none of that fully closes the gap — but on first-floor additions, tight-access urban sites or design-led schemes it frequently does.
Regs, insurance and the alternatives to weigh up
For houses, building regulations treat CLT extensions like any other structure — Approved Document B fire provisions are readily met at domestic scale (the exposed-timber restrictions that affect tall buildings don't apply to a two-storey home), and U-values are hit with external insulation over the panel. Do check that your builder has CLT experience and that your structural warranty or insurer is comfortable with mass timber — a specialist supply-and-erect subcontractor alongside a general builder is the common model.
Before committing, compare the neighbouring systems: our guides on steel-frame extensions and SIPs panel extensions cover the same question for those systems. Benchmark your budget with the house extension cost guide and extension cost calculator, then get like-for-like prices from vetted firms via our free quote service.
Get CLT and Blockwork Quotes Side by Side
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Frequently asked questions
Related Guides
More guides to help you plan and budget.
Sources used in our 2026 figures
- Structural Timber Association — engineered timber guidance
- Timber Development UK — timber construction resources
- gov.uk — Approved Document B (fire safety)
Methodology: Rates reflect fitted, VAT-inclusive quotes and supplier panel pricing gathered Q2–Q3 2026 for typical 20m² single-storey extensions; regional variation applies. Always price both systems against identical drawings. Last updated .