Timber cladding has become one of the most popular exterior finishes for residential extensions across London and the wider UK. From contemporary rear extensions clad in charred timber to garden room offices wrapped in Siberian Larch or ThermoWood shadow gap, the options available to homeowners have expanded significantly. But with that choice comes complexity — particularly around fire performance requirements and understanding the real cost before committing to a design.
Do residential extensions need fire rated cladding?
This is one of the most common questions homeowners face when planning a clad extension. The answer depends on several factors: the height of the building, its proximity to a neighbouring property boundary, and any specific planning or building control conditions attached to the project.
For most single-storey residential extensions in England, standard untreated timber cladding does not require fire retardant treatment — provided the extension falls within permitted development parameters and there are no boundary proximity issues. However, extensions on buildings above two storeys, projects in certain conservation areas, and any scheme where building regulations require a higher reaction-to-fire classification will need a treated system.
For homeowners and developers whose projects require a confirmed fire classification, fire rated cladding for residential extensions UK is available as a factory-applied service. Boards are pressure-impregnated before delivery, arriving on site with the required Euroclass B classification already achieved and documented — simplifying the building control submission and removing the risk of on-site treatment inconsistencies.
If you are unsure whether your project requires fire rated cladding, confirm the requirement with building control at pre-application stage. This is typically a free service and takes the guesswork out of specification before any materials are procured.
How much does timber cladding cost for a home extension?
Cladding costs vary considerably depending on species, profile, finish, and whether boards are supplied standard or factory-coated. Understanding the cost range before finalising a design avoids budget surprises at procurement stage.
As a general guide for 2026, Siberian Larch is typically the most accessible premium timber cladding option, with supply-only costs commonly in the £20 to £40 per m² range depending on profile. ThermoWood — thermally modified timber with improved stability and a longer service life — typically falls in the £45 to £75 per m² range. Charred timber and fire retardant treated boards command a premium, often £60 to £95 per m² or above.
For a full breakdown of current pricing by species and profile, the timber cladding cost per m² UK 2026 guide covers supply costs across ThermoWood, Siberian Larch, Nordic Spruce, and charred timber, with practical guidance on quantity calculation and budgeting for fixings and accessories.
Installation adds significantly to the total budget. Professional timber cladding installation in the UK typically ranges from £30 to £60 per m² for labour, depending on elevation complexity, number of openings, and the fixing system specified. For a typical 40m² rear extension elevation, total installed costs commonly fall between £2,500 and £6,000 depending on specification.
Choosing the right timber for your extension
Beyond cost and fire performance, the right choice of timber cladding depends on three practical considerations: how much maintenance you are prepared to carry out, how you want the material to age visually, and how the finish relates to the character of the existing property and its setting.
Both ThermoWood and Siberian Larch weather naturally to silver-grey when left untreated — a look that suits contemporary extensions well and requires very little ongoing maintenance beyond periodic inspection. If retaining the original warm timber tone is important, a regular oil or coating programme is needed, with south-facing elevations typically requiring more frequent attention.
For extensions in conservation areas, or where a painted finish is required by planning condition, factory-coated boards offer the most consistent and durable result. Coating applied under controlled factory conditions before installation significantly extends the interval between maintenance cycles compared with site-applied finishes.
Whichever species and finish you choose, specifying a ventilated rainscreen installation — with a drained and ventilated cavity between the cladding boards and the wall structure — is strongly recommended for all UK residential extensions. This detail manages moisture, extends cladding life, and is standard practice among reputable cladding installers across London and the wider UK.
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