How to Build a Sauna Bench - Dimensions, Heights, and Spacing That Actually Work

You’ve got the sauna shell built or the kit delivered, and now you’re staring at a pile of lumber wondering how high the benches should actually sit. This is the part people rush, and it’s the part that decides whether your sauna feels great or just okay every single session. Get the bench dimensions right and the room does its job without you thinking about it. Get them wrong and you’ll be shuffling around a bench that’s too low to feel the heat properly, or too high to climb onto comfortably after a long day.

What you need to know before you cut anything

Sauna benches work in tiers because heat stratifies. The air near the ceiling can run 30 to 50°C (55 to 90°F) hotter than the air near the floor, sometimes more depending on room height and heater output, so where you sit changes your whole experience. A tiered bench setup lets you choose your temperature by choosing your seat, which is the entire point of building more than one level.

Most home saunas use two tiers: an upper sitting bench and a lower bench that doubles as a footrest or a cooler seat for anyone who wants a gentler session. Bigger saunas sometimes add a third tier, but two levels covers the vast majority of home builds and keeps the room simpler to insulate and heat evenly.

Before you touch a saw, decide who’s using this sauna. A bench sized for a household of adults who mostly sit will differ slightly from one built so people can stretch out and lie down, which is the traditional way to take a proper sauna and genuinely more comfortable for a long session.

Bench heights, depths, and spacing

Here’s where the actual numbers live. Treat these as a solid starting range, not a single magic figure. Real builds vary by ceiling height, room size, and who’s using the sauna.

Upper (sitting) bench height. Aim for roughly 90 to 110 cm (35 to 43 in) off the floor, with some traditional Finnish builds going a bit higher, up to around 120 cm (47 in), in taller rooms. Higher puts you in noticeably hotter air, which is exactly why it’s the seat of choice for people chasing serious heat. If your household includes shorter people or kids, don’t just chase the upper end of that range because it sounds more authentic. A bench nobody can climb onto without a step stool isn’t better sauna.

Lower bench height. Somewhere around 45 to 60 cm (18 to 24 in) works for most builds. This tier sits in noticeably cooler air, which makes it the right spot for beginners, longer sessions, or anyone easing back into heat after a break.

Step riser consistency. If you’re adding a step between floor and lower bench, or lower and upper bench, keep every riser the same height, somewhere in the 35 to 45 cm range mirrors a normal stair rise and won’t trip anyone reaching for a towel in low light. Mismatched riser heights are a genuinely common reason people stub a toe or misjudge a step in a dim, steamy room.

Upper bench depth. Give it at least 50 to 60 cm (20 to 24 in) if people will only be sitting. If you want anyone to be able to lie down, which is worth building toward if your room allows it, push the depth closer to 60 cm (24 in) or a touch more. Lying down properly, rather than sitting hunched, is a big part of why a well built sauna bench feels so much better than a bare platform.

Lower bench depth. This tier can run shallower since it’s mostly a footrest and secondary seat, roughly 35 to 50 cm (14 to 20 in) is plenty. Don’t go so narrow that it stops being usable as an actual seat when the sauna’s full and someone needs a cooler spot.

Width per person. Budget about 60 cm (24 in) of bench length per seated person so elbows and knees have room. Tight benches make a two person sauna feel like a three person squeeze the moment you invite a friend.

Board spacing. Leave a small gap between boards, roughly 0.6 to 1.5 cm (1/4 to 1/2 in), so water and sweat can drain and air can move underneath. Stay inside that range: narrower and the gap tends to swell shut as the wood absorbs moisture, wider and it starts to pinch skin on the backs of thighs. Tight, gapless boards trap moisture against the wood, which speeds up staining, warping, and eventually rot. This is one of those details that’s invisible until you skip it, and then it’s very visible.

Building the frame

Two common approaches work well for home builds.

A ledger and cross-support system bolts a horizontal board (commonly a 2x4 or 2x6) directly into the wall studs at your chosen bench height, then runs cross supports out to a front rail every 40 to 60 cm (16 to 24 in), tightening toward the 40 cm end for longer runs or if you’d rather not risk sag. This is the tidier option because it hides the structure and keeps the underside of the bench open for airflow.

A leg-supported bench is simpler to build if you’re not confident drilling into studs at the right height, with legs spaced roughly every 60 to 75 cm (24 to 30 in) along the run. It’s a bit more visually busy but easier to adjust or replace later.

Either way, don’t skimp on support spacing just because the wood looks strong. Sauna heat cycles the wood through repeated expansion and contraction, and a frame that’s underbuilt will start to squeak, sag, or flex within a season or two of real use.

Wood choice actually matters here

This is where a lot of DIY builds go wrong: people use whatever lumber is cheap and available, and then wonder why the bench gets uncomfortably hot to sit on. Sauna heat means bench wood needs to be genuinely low in thermal conductivity, not just “sauna adjacent” softwood.

Aspen, alder, and abachi (sometimes sold as African ayous) are the standard picks for exactly this reason: they stay cooler to the touch at sauna temperatures than most other woods, they’re low in resin, and they don’t carry strong scent compounds that can bother people who are sensitive to them. Cedar shows up a lot in outdoor and structural sauna builds for its rot resistance, but it can run hotter under bare skin and isn’t everyone’s first choice for the actual seating surface.

Whatever you pick, avoid boards with visible resin pockets or knots. Resin heats up and can genuinely burn skin on contact, which is not a subtle problem once it happens. Skip anything stained, varnished, or chemically treated too. Those finishes off-gas at sauna temperatures, and that’s not something you want to be breathing in a small, hot, enclosed room.

Honest caveats

None of these numbers are building code. Sauna dimensions are a strong, well tested convention, not a legal requirement, and you’ll find real builds and reputable guides that land a few centimeters outside every range here. If your ceiling is on the low side, you may need to compress the tier heights to keep proper clearance above the top bench, and that’s a legitimate reason to deviate.

Also don’t over-engineer this. A sauna bench is a wet, hot, heavily used piece of furniture, not fine cabinetry. Simple, well supported, properly spaced boards will outlast a complicated design with tight joinery that traps moisture in the corners.

And resist the urge to add a third tier just because you can. More tiers means more air to heat and more complexity in the frame, and for most home saunas built for two to four people, two well proportioned tiers beat three cramped ones.

The takeaway

Get the tiers right and the bench does the hard work of letting everyone choose their own heat without anyone needing to say a word about it. Rough numbers to work from: upper bench around 90 to 110 cm high and 50 to 60 cm deep, lower bench around 45 to 60 cm high and 35 to 50 cm deep, consistent step risers, small drainage gaps between boards, and wood that’s actually built for the heat rather than just resistant to rot. Build to those ranges, adjust for your room and your household, and you’ll end up with a bench that disappears into the background of a good sauna session, which is exactly where it belongs.