Sauna Bench and Backrest Design: Height, Wood, and Lighting

A sauna bench is not furniture you drop into a finished room. Its height decides which temperature zone your body sits in. Its depth, wood, backrest, and lighting decide whether the room is comfortable to actually use.

Start with the bather, not the bench style. Set the foot level in relation to the heater. Set the sitting bench above it. Only then choose wood, backrest, and lighting.

The short version:

Set Bench Height Before You Choose a Bench Style

Bench height is not a style choice. It sets whether your whole body sits in the sauna's warm zone or spans two different temperature zones at once.

• The Finnish Sauna Society places the foot bench 100 to 200 mm (4 to 8 in) above the top of the heater stones, with the upper sitting bench about 450 mm (18 in) above the foot bench, and the ceiling 1000 to 1200 mm (39 to 47 in) above that upper bench.¹

Ventilation and air mixing affect how evenly that heat actually distributes, and every heater has its own installation clearances. Treat the figures above as planning guidance, then check your specific heater's manual before finalizing the layout. We cover the full temperature-zone mechanics, plus ceiling shape and ventilation, in Common Home Sauna Design Mistakes (and How to Fix Them). This article focuses on the bench itself.

Give the Bench Real Depth, Not Just Seats

Bench depth changes how the sauna can actually be used, not just how many people can sit on a drawing.

• Harvia recommends an upper bench depth of at least 500 mm (20 in), and 600 mm (24 in) or more for lying down or sitting with the feet up.² The Finnish Sauna Society uses a similar 600 mm of depth and width per adult as a planning reference.¹

Do not trade bench depth for seating capacity. Plan the bench around how the sauna is actually used, not the maximum number of people that fits on paper.

Choose Bench Wood for Skin Contact, Not Just Color

A sauna bench gets sat on, leaned against, and touched with bare skin. That is a different test than wall or ceiling wood has to pass.

• Ilkka's own build recommendation for My Sauna Plus benches is thermally treated aspen: gentle against skin, splinter-free, and slower to heat up than denser woods, with the thermal treatment adding moisture and decay resistance at the cost of a noticeably darker finish than natural aspen.⁴

That preference lines up with the wider guidance for sauna benches. Harvia identifies low-density, porous woods as the common choice because they do not overheat to the touch, and the Finnish Sauna Society lists aspen and alder among the traditional bench species.¹²

Thermal modification is a real trade-off, not simply an upgrade. A 2025 review of thermally modified wood reports improved dimensional stability and better resistance to biological decay, alongside reduced mechanical strength and greater brittleness under some treatment conditions.³ The effect depends on species and process, so treat thermally modified wood as a different material with its own characteristics, not a strictly better version of the untreated species.

If you prefer a pale, understated interior, natural aspen is a valid choice on its own. If you want a deeper brown tone and the added decay resistance, thermally treated aspen is the trade worth making. Either way, buy stock rated for sauna use rather than choosing on color alone. Browse bench-adjacent comfort options, including seat cushions, in our sauna accessories collection.

Build the Backrest as Part of the Bench, Not an Afterthought

A backrest is not a finishing detail added at the end. It takes up real bench depth, so plan it with the seating, not after the seating is already built.

• Ilkka's own installation technique uses small cut wood blocks as temporary spacers to set the backrest's position and gap before fastening it. The spacers come out once the backrest is secured.⁴

Account for how far the backrest projects from the wall before you finalize bench depth. A bench that measures 600 mm on paper measures less than that in usable seat space once a backrest is mounted against it.

Wire Backrest Lighting Before the Woodwork Closes Access

Lighting is the easiest detail to solve early and the hardest to fix late.

• Ilkka's own sequencing rule: run wiring for any concealed lighting before the benches go in. Fitting it in cleanly afterward is nearly impossible.⁴

Dimmable LED strips placed behind the backrest, aimed up or down rather than straight out, keep the light source out of the bather's direct line of sight and wash the wood or wall in soft, indirect light.

The lighting effect does not decide whether a fixture belongs in a sauna. Our own sauna lighting collection is built around fixtures rated for the room: heat resistance to 250°F, an IP65 or higher waterproof rating, and electrical drivers placed outside the sauna room rather than inside it.⁵ Match any concealed lighting to those specifications and follow the fixture manufacturer's install instructions and applicable electrical code, not the reverse.

A Better Sequence for Sauna Bench Design

Do not start a bench design with a wood species or an inspiration photo. Start with the bather, then work outward:

Working in this order keeps the bench tied to how heat actually moves through the room, instead of treating it as furniture added after the room is already decided.

Read Common Home Sauna Design Mistakes for the ceiling and ventilation side of this same design process, or Finishing a Sauna Interior Without Costly Mistakes for the full room-closing sequence this bench work fits into, wiring, vents, and heater placement included. For the full path from room size to installation, see our buyer's guide. Browse bench-adjacent comfort pieces in sauna accessories and sauna-rated fixtures in sauna lighting. If you are planning a build and want a second opinion on the layout, schedule a free expert consultation.

Sources

1. Liikkanen, Lassi A. "Lauteiden suunnittelu, lyhyt oppimäärä." Sauna-lehti, Suomen Saunaseura ry (Finnish Sauna Society), February 9, 2023. sauna.fi. Confirms the foot bench height (100 to 200 mm above the heater stones), the foot-bench-to-upper-bench height (450 mm), the ceiling clearance above the upper bench (1000 to 1200 mm), and the roughly 600 mm of bench depth and width per adult, all fetched and verified against this exact source text.
2. Harvia. "What to Consider When Choosing Sauna Benches: Frequently Asked Questions." harvia.com. Confirms the recommended upper bench depth (at least 500 mm, 600 mm or more to lie down) and the preference for low-density, porous bench woods.
3. Jančíková, Veronika, and Michal Jablonský. "Thermal Modification of Wood: A Review." Sustainable Chemistry, Vol. 6, No. 3, Article 19, July 11, 2025. DOI: 10.3390/suschem6030019. mdpi.com. Confirms the dimensional-stability and decay-resistance gains of thermal modification alongside its mechanical-strength and brittleness trade-offs.
4. My Sauna Plus source video transcripts, pulled 2026-09-10: "This bench mistake makes your head overheat while your feet freeze" (YouTube Shorts, pMvdaqxkbB4), "BUILD BENCHES THAT LAST" (rNhsJZ-mCtQ), and "THE BACKREST TRICK PRO BUILDERS USE" (cRgI43lgelU). Source of Ilkka's own stated build recommendation for thermally treated aspen, the temporary-spacer backrest installation technique, and the wire-before-benches lighting sequencing. Presented here as My Sauna Plus's own field experience, not as an independently verified industry standard.
5. My Sauna Plus, Sauna Lighting collection page. Confirmed live 2026-09-19. mysaunaplus.com/collections/sauna-lighting. Confirms the heat-resistance (250°F), waterproof rating (IP65 or higher), and outside-the-room driver placement that sauna-rated lighting fixtures on this site are built to.