- Most specified species: Siberian larch shadow gap 20x146mm — Class 3 durability, no treatment, 20–30 years, clean contemporary profile suited to most extension designs.
- Zero maintenance alternative: ThermoWood — Class 2, 25–40 years, zero maintenance, most dimensionally stable species.
- Most popular profiles: Shadow gap for contemporary. Shiplap for traditional or rural. Charred or black-stained for bold contemporary extensions.
- Cost: Supply only from £25–55/m² depending on species. Supply and install typically £60–120/m² all in.
- Planning: Permitted development often applies — but conservation areas, listed buildings, and Article 4 areas require consent. Always check first.
- Value added: Timber cladding on a house extension adds value — particularly where it signals design quality through contrast with the existing house material.
Timber cladding is one of the most popular exterior finish choices for house extensions in the UK — used on rear extensions, side extensions, garden rooms, and full house reclads to add contemporary character, design quality, and a zero-maintenance natural facade that performs reliably for 20–40 years. This guide covers everything you need to know about timber cladding for house extensions in the UK in 2026 — the best species, profiles, colours, costs, planning requirements, and how to specify correctly to avoid the most common mistakes.
Siberian larch cladding on a contemporary house extension — the warm honey-gold of fresh larch weathers naturally to silver-grey over time, requiring no treatment throughout its 20–30 year service life. Shadow gap is the most widely specified profile for contemporary extensions across the UK.
Why Timber Cladding Works So Well on House Extensions
Timber cladding on a house extension does something that most other exterior materials cannot — it deliberately reads as different from the existing house, using contrast to signal that the extension is a deliberate architectural addition rather than an attempt to blend in. A contemporary larch-clad rear extension on a Victorian brick terraced house in London is now one of the most reproduced residential design moves in the UK, and for good reason: it works. The warm natural material, the horizontal shadow line of the cladding profile, and the absence of mortar joints and brickwork detail create an extension that reads as contemporary and designed without being out of place.
Beyond aesthetics, naturally durable timber cladding on a house extension offers practical advantages that matter over a 20–30 year ownership period:
- Zero maintenance on naturally durable species: Siberian larch (Class 3) and ThermoWood (Class 2) require no preservative treatment, painting, or staining throughout their service life. Left untreated, they weather to a silver-grey that most homeowners find more attractive than the fresh honey-gold starting point
- Value addition: Natural timber cladding consistently adds value on UK residential properties — particularly where it signals design intent through contrast. See our full guide on whether timber cladding adds value to a house
- Planning compliance: Natural timber is one of the most widely accepted exterior materials by UK planning authorities across all contexts — rural, suburban, urban, conservation area, and listed building curtilage
- Design flexibility: The range of profiles, finishes, and species available in timber cladding is wider than any other single exterior material — from traditional feather edge to contemporary shadow gap to bold black charred finishes
Best Timber Species for House Extension Cladding UK
| Species | Durability | Service life | Maintenance | Weathered colour | Best for |
|---|---|---|---|---|---|
| Siberian Larch | Class 3 | 20–30 yrs | None required | Honey gold → silver-grey | Most extensions — the default premium specification |
| ThermoWood | Class 2 | 25–40 yrs | Zero | Honey brown → silver-grey | Premium extensions, buy-to-let, where maintenance is a concern |
| Nordic Spruce | Class 4 | 15–20 yrs | Every 2–4 yrs | Pale cream → silver-grey | Budget extensions, charred/black finish, garden rooms |
| Charred Nordic Spruce | Enhanced by charring | 25+ yrs | Minimal | Deep black — permanent | Black/charred extensions, contemporary bold design |
Best Cladding Profiles for House Extensions UK
Clean recessed horizontal shadow line. The dominant profile for contemporary house extensions — works on rear extensions, side returns, and full house reclads. Available in all species. See our larch shadow gap 20x146mm.
Overlapping boards with a machined rebate. Suits rural extensions, cottage-style properties, and projects where planning requires a more traditional profile. More shadow depth than shadow gap. Available in larch, ThermoWood, and spruce.
Open-joint concealed fix. The most architectural profile for extensions — no visible fixings, maximum shadow depth, clean board face. Higher cost due to the concealed fix sub-frame. See our larch rainscreen 20x68mm.
The most traditional profile — tapered overlapping boards. Suits barn-style extensions, rural properties, and planning contexts that require agricultural vernacular references. See our feather edge guide.
Contemporary timber cladding on a London house extension — the horizontal shadow gap profile, warm natural larch, and clean lines create an extension that reads as contemporary and designed without being out of character in an established residential street. This is the most reproduced residential extension cladding aesthetic in the UK.
Black Cladding for House Extensions UK — Charred and Dark Stained
Charred timber cladding on a house extension — the deep black character of charred Nordic spruce creates a bold, contemporary extension that contrasts dramatically with brick or render. Charring carbonises the surface layer, providing genuine weather resistance and reducing the maintenance obligation compared to standard stained softwood.
Black and dark-finished timber cladding for house extensions has become one of the most searched and specified finishes in the UK residential market — driven by the growth in contemporary rear extensions where bold contrast with the existing Victorian or Edwardian brickwork is the design intent. The two main approaches:
- Charred / Shou Sugi Ban inspired: Deep charring of Nordic spruce boards carbonises the surface layer, producing a near-black matte finish with visible grain texture. The carbonised surface provides genuine weather resistance — reducing maintenance significantly compared to black-stained untreated softwood. Our Shou Sugi Ban range includes charred, brushed, and stained black finishes on Nordic spruce and Siberian larch. See our full charred cladding guide for the complete picture
- Black-stained or dark-treated larch: Factory or site-applied black or near-black stain on Siberian larch — produces a consistent, slightly less rustic dark finish than charring. Requires re-staining every 5–7 years. More uniform in appearance than charred boards — suits contemporary extensions where a very clean, consistent dark finish is the design intent
Black-treated timber cladding on a contemporary house extension — a factory-applied dark stain on Siberian larch produces a consistent, uniform dark finish suited to extensions where a very clean, contemporary aesthetic is the design intent. Consistent colour across large elevations is easier to achieve with factory-applied stain than site application.
How Much Does It Cost to Clad a House Extension UK? 2026 Prices
| Specification | Supply only (per m²) | Supply & install (per m²) | Typical 25m² extension total |
|---|---|---|---|
| Nordic spruce feather edge / shiplap | £8–15/m² | £35–55/m² | £875–1,375 |
| Siberian larch shiplap 20x146mm | £25–35/m² | £55–80/m² | £1,375–2,000 |
| Siberian larch shadow gap 20x146mm | £30–40/m² | £60–90/m² | £1,500–2,250 |
| Charred Nordic spruce (Shou Sugi Ban) | £35–50/m² | £65–95/m² | £1,625–2,375 |
| ThermoWood shadow gap | £40–55/m² | £70–100/m² | £1,750–2,500 |
| Siberian larch rainscreen (hidden fix) | £35–50/m² | £75–120/m² | £1,875–3,000 |
All prices include batten system and fixings for supply-and-install figures. Supply-only prices are for boards only. See our full cost to clad a house extension guide and our timber cladding cost per m² guide for detailed pricing breakdowns.
Planning Permission for Timber Cladding on a House Extension UK
Planning requirements for timber cladding on house extensions depend on whether the extension itself required planning permission, and whether the property is in a restricted area:
- Extensions built under permitted development: If the extension was built under permitted development rights, the external cladding material may also fall under permitted development — provided the material is of similar appearance to the existing house. However, this is a grey area and local planning authorities interpret it differently. If in doubt, seek written confirmation from your local planning authority before cladding
- Extensions requiring full planning permission: The approved external materials will typically be specified as a condition of consent. Changing to timber cladding requires a non-material amendment or formal material amendment application
- Conservation areas: In conservation areas, any change to the external appearance of a dwelling — including adding cladding to an extension — requires a householder planning application. Natural timber is generally well received in conservation areas but the specific profile and finish will need to be approved
- Listed buildings: Any external material change on a listed building or its curtilage requires listed building consent in addition to any planning permission required
Specifying Nordic spruce (Class 4) on a house extension because it is cheaper, without factoring in the maintenance obligation. A 2–4 year preservative treatment cycle on a rear extension requires scaffolding or access equipment, a professional treatment contractor, and typically costs £300–800 per treatment visit. Over 20 years, the cumulative maintenance cost of treated spruce routinely exceeds the initial saving on board cost over naturally durable Siberian larch. Specify larch or ThermoWood and remove the obligation entirely. See our timber cladding maintenance guide for the full picture.
What is the best timber cladding for a house extension UK?
Siberian larch shadow gap 20x146mm — Class 3, no treatment required, 20–30 years, clean contemporary profile. ThermoWood for zero maintenance. Charred Nordic spruce for black extensions. The choice of profile depends on the design intent — shadow gap for contemporary, shiplap for traditional, rainscreen for high-spec architectural projects.
Do you need planning permission to clad a house extension UK?
It depends on how the extension was built and where the property is. Permitted development extensions may allow cladding without consent if the material is of similar appearance to the existing house. Conservation areas and listed buildings always require consent for external material changes. Always check with your local planning authority before cladding.
How much does it cost to clad a house extension UK?
Supply and install typically £60–120/m² depending on species and profile. A typical 25m² single-storey rear extension costs £1,500–3,000 all in for timber cladding. Siberian larch shadow gap supply only from £30–40/m². Nordic spruce from £8–15/m² supply only. ThermoWood from £40–55/m² supply only.
Does timber cladding on a house extension add value?
Yes — particularly where it creates a deliberate contrast with the existing house material. A contemporary larch-clad extension on a Victorian brick house is widely recognised by surveyors and estate agents as a quality addition. The value addition is most pronounced where the cladding signals design quality and the species is naturally durable (no maintenance obligation for future buyers).
Timber Cladding for House Extensions — Supply Nationwide
We supply Siberian larch, ThermoWood, Nordic spruce, and charred cladding for house extensions across the UK. Shadow gap, shiplap, rainscreen, and feather edge profiles. Natural, grey, and black finishes. FSC and PEFC certified. 7–14 day delivery. Contact us for a quote or free samples.