Choose timber by its job
The “best wood” depends on where it is used
A hot tub may have a water-retaining liner, timber cladding and separate structural parts. A sauna has external cladding, framing, benches and an interior exposed to heat. Comparing species without naming the component leads to the wrong conclusion.
First identify what the timber is doing
Water retention
In a solid-timber vessel, the staves themselves retain water. In a liner-based model, the liner is the water-retaining component and the timber may be external cladding.
Exterior cladding
Cladding provides appearance and weather protection but still needs suitable detailing, drying and maintenance for the exposure.
Sauna interior
Benches and internal linings are chosen for heat behaviour, comfort, low splinter risk and indoor-sauna conditions—not simply outdoor durability.
Structure
Frames, runners and supports are specified for strength, moisture exposure and the construction system. They may differ from the visible finish.
Common timber choices in outdoor-wellness products
| Timber | Why buyers consider it | Where it may suit | Points to confirm |
|---|---|---|---|
| Thermowood | Thermal modification improves dimensional stability and gives a warm, even appearance. | Exterior cladding and selected sauna applications, depending on grade and component. | Exact species, modification class, surface treatment and whether colour change is acceptable. |
| Larch | Dense softwood character, visible grain and useful natural durability for many external applications. | Outdoor cladding and selected structural or decorative components. | Grade, detailing, resin, checking and the maintenance finish. |
| Spruce | Light colour, familiar Nordic appearance and efficient use in protected construction. | Sauna structures, interiors or cladding when the grade and exposure are appropriate. | Whether the component is weather-exposed, the treatment and ventilation details. |
| Western red cedar | Low density, characteristic aroma and natural durability valued in premium outdoor work. | Selected cladding, sauna and solid-timber applications when correctly specified. | Species authenticity, grade, colour variation, availability and price. |
| Redwood / pine grades | Workable, widely available and suitable for many treated or protected applications. | Frames, cladding and components where the treatment system matches the exposure. | Exact commercial species, treatment, grade and permitted finish. |
| Accoya and other modified woods | High dimensional stability and durability from a controlled modification process. | Premium external components where the product design and budget justify it. | Availability, approved coatings, fixings, warranty and model-specific compatibility. |
Hot tubs
Solid timber vessel or timber-clad liner?
This is the most important distinction. A solid-timber tub relies on accurately made staves and controlled swelling to hold water. It behaves differently from a fibreglass or polypropylene liner surrounded by timber cladding.
For a liner-based model, compare the liner material and support system separately from the exterior wood. The cladding can often be selected for appearance and weathering preference without changing the water-retaining body.
- Confirm what actually holds the water.
- Ask which timber is structural and which is decorative.
- Check whether the selected finish is factory applied.
- Use only cleaning and coating products approved for that component.
Outdoor saunas
Separate the weather shell from the hot room
The exterior must manage rain, sun and drying. The hot-room lining and benches must remain comfortable at operating temperature and be detailed for ventilation and cleaning. The same species can sometimes appear in both areas, but the grade, profile and treatment should still be specified by component.
Never apply an exterior coating to sauna benches or interior surfaces unless the product manufacturer explicitly approves that use. Internal finishes must be suitable for the temperature and skin contact involved.
Appearance and maintenance over time
Untreated exterior timber normally changes colour under UV and weather exposure. This is not the same as structural decay. A pigmented, compatible finish can slow visible greying, while good detailing helps surfaces dry after rain.
- Identify the supplied wood and factory finish. Keep the order specification and care instructions.
- Inspect before coating. Look for dirt, trapped moisture, failed sealant and mechanical damage.
- Use compatible products. Test a discreet area and respect drying times and temperature limits.
- Avoid aggressive cleaning. High pressure and harsh chemistry can raise fibres or damage finishes.
- Maintain drainage and ventilation. No coating compensates for persistent water traps.
Timber-selection questions
Is cedar always the best wood for a hot tub?
No. It is a valued premium timber, but the correct choice depends on whether the wood retains water, forms cladding, carries load or is used inside a sauna.
Does Thermowood require no maintenance?
No. Thermal modification improves material properties but does not prevent weathering, dirt, surface checking or colour change. Care depends on the component and desired appearance.
Can exterior sauna timber be treated with any decking oil?
No. Confirm compatibility with the supplied timber and factory finish. Keep exterior products away from hot-room surfaces unless approved for that use.
Why can photographs of the same model show different timber tones?
Natural variation, exposure, age, lighting, finish and configurable wood options all affect appearance. The written order identifies the supplied choice.
Compare like with like
Ask for the material by component
Confirm the liner or vessel, cladding, structure and sauna-interior materials separately in the final specification.
