Timber species / Thermally modified softwood
Thermowood
cladding.
Thermowood is heat modified to improve stability and durability without chemical preservatives. Its consistent colour, light weight and predictable movement make it an excellent all-round cladding material.
Request Thermowood pricing →Thermowood cladding
Specify the timber, modification and finished board.
Thermowood cladding is selected for its warm starting colour, precise machining and the altered moisture behaviour created by thermal modification. Those qualities do not make every brown, heat-modified board interchangeable. Source species, grade, modification process, product class, dimensions and intended exterior use should all appear in the quotation.
The term ThermoWood® has a specific meaning. The International ThermoWood Association's 2025 handbook describes it as a registered trademark used by association members whose production is subject to audited quality control. “Thermally modified timber” is a broader description, so ask what process and evidence support the actual product being offered.
A representative sample set is more useful than one selected board. Review the grade, knots, surface texture, profile joint and colour range together. For a large or closely viewed elevation, a joined sample panel provides a better basis for approving board rhythm, fixings and finish.
Product class and exterior use
Ask what the declared class proves for the product.
The ThermoWood® system distinguishes Thermo-S and Thermo-D product classes. The handbook explains that S refers to stability and D to durability, with separate data for softwood and hardwood products. A class name should be read alongside the species, manufacturer information and intended application rather than used as a stand-alone specification.
For exterior cladding, request the current technical sheet, profile drawing and installation guidance for the exact product. Confirm board orientation, finished dimensions, installed cover, fixing zone, support arrangement and treatment of cut ends. The wall still needs a coordinated cavity, membrane, battens, flashings and junction details.
- 01Name the source species and supplied grade
- 02Record the process, producer and product class
- 03Confirm exterior application and board orientation
- 04Request technical, installation and maintenance evidence
Plan colour, sourcing and compliance as separate decisions.
Uncoated thermally modified timber changes colour outdoors. Where the initial brown tone matters, ask the board and coating suppliers to confirm compatible preparation, application, end-grain treatment and maintenance. If certified sourcing is required, request the chain-of-custody claim and certificate details that apply to the order; PEFC explains how certified material is tracked through the supply chain. Fire performance and regulatory suitability depend on the complete external-wall design, building and product evidence—not the Thermowood name alone. The appointed team should check the current Approved Document B guidance for England.
Profiles, prices and quotation scope
Compare installed coverage and the complete package.
Thermowood may be offered in tongue-and-groove, shadow-gap, shiplap, board-on-board and open-rainscreen arrangements, subject to the manufacturer's range. Profile names are not standard dimensions. Ask for finished thickness, overall width, installed cover, joint geometry and fixing position.
Price is shaped by species, class, grade, profile, length mix, texture, finish, quantity and documentation. Send each supplier the same elevations, openings, direction, postcode and programme, then compare boards, battens, fixings, trims, finish and delivery on the same basis. Our guide to what Thermowood cladding is covers the process, appearance and maintenance choices behind that shortlist.
- 01Drawings, openings and approximate quantity
- 02Profile, direction and installed cover
- 03Grade, texture, finish and accessories
- 04Documentation, delivery access and required date
Why choose Thermowood?
A material with its own point of view.
Thermowood is heat modified to improve stability and durability without chemical preservatives. Its consistent colour, light weight and predictable movement make it an excellent all-round cladding material.
- 01Improved dimensional stability
- 02Chemical-free thermal modification
- 03Consistent contemporary appearance
- 04Suitable for demanding exterior applications
Colour & weathering
Choose the finish — then plan for how it changes.
Exterior timber naturally responds to sunlight and weather. Left unfinished, most species gradually soften towards silver-grey. Coatings can slow this change or establish a more uniform tone. We’ll help you factor appearance, exposure and maintenance into the decision.
Available directions
One timber. Many expressions.
Before you request pricing
Thermowood cladding questions.
What is Thermowood cladding?
Thermowood cladding is made from timber whose properties have been altered using controlled heat and steam. ThermoWood® is a registered trademark for products made by members of the International ThermoWood Association under its audited quality-control system; other thermally modified timber products may use different processes and evidence.
Is Thermowood suitable for exterior cladding?
Thermally modified timber is widely used for exterior cladding, but suitability must be confirmed for the exact species, product class, profile, orientation, exposure and wall design being proposed. Request the current manufacturer's technical and installation information with the quotation.
Does Thermowood cladding need a finish?
A finish is not only an aesthetic decision. Uncoated boards will change colour outdoors, while a compatible surface treatment can help retain the original tone and reduce surface weathering. Confirm preparation, end-grain treatment, application and maintenance with the board and finish suppliers.
What affects Thermowood cladding prices?
Source species, product class, grade, finished dimensions, installed cover, profile, length mix, surface texture, coating, fire-treatment requirements, accessories, documentation, quantity and delivery all affect the quotation. Compare complete supply scope and installed coverage rather than headline board price.