A sauna backrest is one of those small details that changes how long you actually want to stay in the room. Sit upright on a flat bench with nothing behind you and your lower back starts complaining around minute ten. Add a curved backrest and you can comfortably sit through a full round.

It's also one of the easier upgrades to get wrong. A backrest sits on the hottest wall in the room, and it has to be built so it doesn't trap heat, collect moisture, or burn you. This post covers where it goes, how high to make it, what to build it from, and how to build the curved lumbar version we like.

Do you actually need a sauna backrest?

Not every sauna needs one. If your sessions are short and you spend most of them lying down on the upper bench, a flat wall behind you is fine. If you sit upright and stay a while, a backrest is worth building.

The practical question is what you do in there. Sitting upright to talk with someone or read for 20-30 minutes? Add a backrest. Stretching, lying down, or moving between positions? Skip it, or make it a limited section so you aren't giving up bench length.

There's also a layout reason. In an L-shaped or U-shaped sauna, the corners and the long wall are where people end up leaning, so that's where backrests do the most good. In a small room, a full-length backrest can eat clearance you need, so run the numbers first. Our sauna size guide and floor plan layouts help you check this before you build.

Why the wall behind a backrest matters

Here's the part people miss. The wall behind the upper bench is already the hottest place you can sit, because heat collects near the ceiling. When you lean on a solid wall, you're pressing your back against the hottest, driest surface in the room, with no air moving behind you.

A backrest that stands off the wall fixes that. Leaving a gap between the backrest and the wall lets air move behind it, keeps the back from getting hot-spotted, and gives moisture a way to leave. It also means your skin touches a slatted surface that has had time to shed heat, not a solid board pressed against hot framing.

The same principle applies to the bench itself. Bench slats are spaced so air and moisture move through them, and a backrest should do the same job vertically. If you want the broader picture on why the upper bench sits where it does, read our sauna bench height guide.

Where the backrest goes and how high

Placement is straightforward. The backrest goes on the wall behind the upper bench, because that's where people sit and lean. Lower benches usually don't get one. People on the lower bench are sitting up less, and a backrest down there tends to get in the way of the upper bench's legroom.

For the upper bench in our designs, the seat is typically 40-48 inches below the interior ceiling, and the seating depth is about 24 inches. That depth matters. If the bench is shallow, a backrest eats the space you'd use to sit, and you end up perched on the edge. At 24 inches, you have room to sit with a backrest and still get your legs up when you want to.

For height, think of it as supporting the lumbar spine and mid-back, not as a chair back. A backrest that runs from roughly the seat up to about shoulder height is plenty. Going all the way to the ceiling gains you nothing and puts more wood in the hottest zone.

A note on heat: the hottest air is near the ceiling, so keep the top edge well below it. If you're building with a tight ceiling, see our post on a 7-foot ceiling sauna for how to handle the compromises.

What to build a sauna backrest from

The same rules apply here as for the rest of the interior. Use a low-density softwood that doesn't get too hot to touch. Cedar is the usual choice for backrests because it stays comfortable against skin and resists moisture. Aspen, alder, and hemlock also work. Our comparison of cedar vs hemlock vs aspen goes through the trade-offs.

Whatever wood you choose, a few rules hold:

Fasteners should be stainless steel, and they should never be exposed where your skin touches. Metal gets hot and will burn you. Drive screws from the back or underneath, or recess them and plug them.

Avoid finishes. Raw wood only. Oils and stains cook, smell, and can produce fumes you don't want to breathe. See our post on sauna wood treatment.

Round every edge you can. Backrests get leaned on, and a sharp corner at your shoulder blade gets old fast.

How to build a curved lumbar backrest

This is the design we like, and it's easy to build with basic tools. The idea is a set of gently curved vertical supports with horizontal slats across them. The curve follows your lumbar spine, and the slats and gaps let air through.

Materials

You'll need cedar 1x4s for the curved supports and cedar 1x2s for the horizontal slats, stainless steel screws, and a way to cut a gentle arc, usually a jigsaw. A router with a roundover bit is useful for softening edges.

Step by step

Cut three or four arched supports from 1x4 cedar. Each one is a gentle curve, roughly 2-3 inches of arc over about 16 inches of height. Don't overdo the curve. A tight arc pushes you forward off the wall, and a gentle one supports your lower back without feeling like a ramp.

Mount the supports vertically to the wall behind the upper bench, spaced about 12-16 inches apart. Fasten them into studs or blocking, not just the paneling, because they'll take your weight. If you're framing the wall, add blocking where the supports will land. Our post on framing a sauna room shows where blocking goes.

Attach horizontal 1x2 cedar strips across the curved supports, spaced about half an inch apart. Run the first slat low enough to catch the small of your back and work upward. The gaps between slats are what keep air moving, so don't close them up.

Sand everything, round the edges, and check every fastener by running your hand over it. Then run a break-in heat cycle before you sit on it. If this is a brand new room, our post on how to break in a new sauna heater covers that.

Optional lighting

If you want a soft glow, you can mount an LED strip behind the backrest, in the gap between the supports and the wall. This only works if the fixture and wiring are rated for sauna temperatures, and it has to stay clear of the heat zone. Check ratings before you buy, and see our sauna lighting ideas for what holds up.

Backrest mistakes to avoid

Most backrest problems come from the same few mistakes.

Building it flush to the wall. With no gap, you lose the airflow benefit and moisture can sit behind it. Leave the space.

Making the curve too aggressive. A backrest that pushes you forward is worse than none at all. Keep the arc gentle.

Putting hardware where skin touches. Screw heads, brackets, and metal strapping get hot. Hide them or avoid them.

Making it too tall. More wood near the ceiling means more surface at the hottest temperature, with no added comfort.

Stealing bench depth. If adding a backrest drops your usable seat below about 20 inches, rethink the design. A comfortable backrest on a cramped bench is not an upgrade.

Skipping the stud blocking. A backrest that's only attached to wall paneling will loosen over time as the wood shrinks and swells.

Backrests in kits and prebuilt saunas

Many prebuilt and kit saunas include a simple backrest, usually a slab or a few slats. These work fine for short sessions, but the benches in many kits sit low, which creates other comfort problems that a backrest won't fix. If you're deciding between a kit and a custom build, our post on whether to buy a sauna kit lays out the trade-offs. A backrest is a nice touch, but bench height and ventilation do most of the work in whether a sauna feels good.

Next steps

If you're designing a sauna and want the bench depth, bench height, and backrest worked out for the way you'll actually use the room, that's what our remote sauna design service does. We draw the benches, supports, and blocking so a builder can put it together without guessing. You can also use the sauna design checklist to work through the details yourself.

Frequently Asked Questions

How high should a sauna backrest be?

Run it from about seat height up to roughly shoulder height. That supports the lumbar spine and mid-back without putting extra wood in the hottest air near the ceiling.

Should a sauna backrest touch the wall?

No. Leave a gap behind it so air and moisture can move. Standing the backrest off the wall on curved supports keeps it from hot-spotting your back and helps it dry.

What wood is best for a sauna backrest?

Cedar is the most common choice because it stays comfortable against skin and handles moisture well. Aspen, alder, and hemlock also work. Use raw, unfinished wood and stainless steel fasteners that stay out of skin contact.

Do I need a backrest on the lower bench?

Usually not. Most people lie down or sit less upright on the lower bench, and a backrest there tends to crowd the upper bench's legroom. Put the backrest behind the upper bench where people lean.