Swell Sport · Outdoor sauna guide

Hemlock vs Japanese Cedar for Outdoor Saunas

Choosing between hemlock and Japanese cedar for an outdoor sauna means comparing the actual timber components and the cabin around them. Start with species, thickness, slat construction and weather protection, then consider the interior finish, seating and care routine. Here is how to compare a hemlock cabin with the Japanese cedar used in Swell’s Cube range.

Japanese cedar: the Cube timber specification

Swell specifies Japanese cedar for its Cube range, with 38mm solid timber.^[1]^[2] Swell confirms that the timber slats are continuous, unjoined pieces with no epoxy or filler repairs. When comparing a hemlock cabin, request the same details: the exact species, wall thickness, which parts use that timber, and whether each slat is one continuous piece. This gives you a component-by-component comparison rather than relying on the timber name alone.

Hemlock: distinguish interior lining from outdoor walls

If a cabin specifies western hemlock, WoodSolutions identifies that species as Tsuga heterophylla and describes it as a pale timber used in construction and joinery. It notes that it is not durable and requires treatment for external use.^[3] Check whether the hemlock is protected internal lining or exposed exterior timber, and ask how the roof, cladding and finish protect it. That guidance applies to western hemlock, not every species sold under the hemlock name. Use only manufacturer-approved finishes in a heated sauna interior.

Ask how the timber pieces are made

Compare the timber you will receive, not just a sample photograph. Request close-up views of slat ends, joints and surface finish, together with the written timber specification. The Cube’s 38mm solid Japanese cedar and continuous unjoined slats give you concrete details to compare against the proposed hemlock wall system. The no-epoxy-or-filler-repairs specification applies to those timber slats; roof layers, glazing and accessories have their own construction details.

Check finishes and any emissions testing

Ask what finishes or treatments are used on the interior, benches and exterior, and how those surfaces should be maintained. If emissions performance matters to your purchase, request a report identifying the finished product, test conditions and components covered. Solid timber and the absence of repair filler describe construction; a whole-cabin emissions claim needs its own evidence.

Compare the entire outdoor weather strategy

Check roof covering, drainage, timber thickness, ground separation, fittings and access for inspection. Swell lists solid Japanese cedar and bitumen roof shingles for the Cube range.^[1]^[2] These features need to be considered together with installation and ongoing care. Ask how the cabin should be cleaned, whether exterior finishing is required and which surfaces must remain untreated. For either Japanese cedar or hemlock, a roof that sheds water, a drained base and access for inspection are practical parts of outdoor ownership.

Choose the construction and interior you want to live with

Request written specifications, component drawings and care instructions, then compare seating, heater packages and installation costs alongside timber choice. If you have a health concern that may affect sauna use, ask your GP for individual advice rather than relying on a timber label. If a supplier makes an emissions or certification claim, ask exactly what was tested. Choose Japanese cedar or hemlock as part of a complete cabin specification: the wall system, protected exterior, comfortable benches and care requirements should all suit your home.