The short answer
- Heat layers are unavoidable. Hot air rises, so a sauna is always hottest under the ceiling and coolest at the floor. Benches are how a design puts people in the right layer.
- The top bench sits high, close to the ceiling. Harvia recommends about 1,100 to 1,200 mm from the upper bench to the ceiling; Finnish guidance gives 1,000 to 1,200 mm.
- The lower bench is mainly a foot rest. A Finnish rule of thumb keeps the bather’s feet above the heater stones so the heat feels even. It is good practice, not a law, and heater design and ventilation affect it.
- Dimensions are ranges, not one number. Harvia, the Finnish Sauna Society and other specialists publish slightly different figures. The room, the heater and the people using it decide the final dimensions.
- Bench timber is chosen for touch. Anything skin rests on should be low-density, clear (knot-free) and resin-free. We use western red cedar, with clear grades wherever skin touches.
- Details make a bench. Rounded edges, concealed stainless fixings from below, airflow under and behind, and sections that lift out.
Why the top bench is hottest
An electric sauna heater warms the room mainly by moving air. Cool air is drawn into the base of the heater, warmed by the elements and stones, and rises to the ceiling. It spreads out, cools and sinks again. The result is a room that settles into layers: the hottest air under the ceiling, a steep fall in temperature down the walls and the coolest air at the floor. Our guide to how a sauna heats explains that loop in more detail.
How steep the difference is surprises many people. Published measurements give a sense of it:
| Source | What was measured | Finding |
|---|---|---|
| Laatikainen-Raussi et al., Temperature (2026); four Finnish saunas in normal use | Air temperature at sitting height and at 1.73 m, minutes 2–10 of sessions with löyly | About 51 °C at sitting height vs about 69 °C at 1.73 m |
| Saunologia.fi pilot test with a Finnish heater maker (2019); 8.5 m³ test room, three heaters | Temperature from ceiling to foot level | About 36 °C difference with a closed-body heater; the smallest spread with a tall, open-mesh heater |
| Harvia, illustrative example in a North American heater manual | Thermometer readings around one room | About 82 °C above the heater, 74 °C on the opposite wall, 60 °C at upper-bench level, 49 °C at lower-bench level and 38 °C at the floor |
These are examples, not targets. The exact figures depend on the heater, the ventilation, the room and where the thermometer sits. The pattern, though, is always the same.
Why this matters: a bather sitting even half a metre lower can be in air ten or more degrees cooler. A room with low benches and a tall ceiling can feel lukewarm at the bench while the control says the room is at temperature.
The sensor reads the hottest air, not the bench
The heater’s temperature sensor goes high, in the hottest part of the room. Harvia’s control manual places it on the wall above a wall-mounted heater, about 100 mm below the ceiling, and keeps it well away from supply vents so incoming air does not cool it. Other manufacturers place it differently (one even forbids putting it directly above its heater), so the selected heater’s manual governs.
Why this matters: the number on the panel is the temperature near the ceiling, not at your back. That is one more reason the upper bench is placed close to the ceiling: it brings the bather nearer the air the heater is controlling.
Feet above the stones
A long-standing Finnish principle, often called the “law of löyly”, says a bather should sit entirely above the top of the heater stones, feet included. It is attributed to the Finnish ethnologist Sakari Pälsi and restated in the Finnish Sauna Society’s Sauna magazine, which suggests setting the foot bench about 100 to 200 mm above the level of the stones. Saunologia.fi, a Finnish sauna research site, states it the same way and notes that some practitioners add a further 100 mm.
The reasoning is simple. Below the stone line, the air is noticeably cooler, so a bather whose feet hang below it has hot shoulders and cool feet.
It should be treated with care:
- It comes from naturally ventilated saunas. Saunologia points out that mechanical ventilation changes the picture.
- Heater design matters as much as height. In Saunologia’s 2019 test, a closed-body heater left a much larger head-to-foot difference than an open-mesh design, and the site suggests heaters that release heat straight up may need up to about 200 mm more.
- Heaters vary widely in height. A compact wall heater and a tall tower heater put the stone line at very different heights, so the same bench heights can satisfy the rule with one heater and fail it with another.
Why this matters: bench heights and heater choice should be decided together. Choose the heater after the benches are drawn, or draw the benches without knowing the heater’s height, and the foot bench may end up in the cool layer.
Upper and lower benches: different jobs
| Upper bench | Lower bench | |
|---|---|---|
| Main role | The main seat, in the hottest air | A foot rest for the upper bench, and a cooler seat |
| Who uses it | Bathers who want full heat; lying down if it is long and deep enough | Children, first-time bathers, anyone wanting a gentler session |
| What sets its height | Distance to the ceiling | Comfortable step below the upper bench, and the heater’s stone line |
| Typical depth | Deeper, for sitting back or lying | Can be shallower if used mainly for feet |
| Design risk | Too far below the ceiling, so bathers sit in cooler air | Below the stone line, so feet sit in cold air |
Two tiers suit most home saunas. A third tier is mainly for taller rooms and larger commercial saunas. One Swedish heater maker’s building guide, for example, treats about 1,900 to 2,200 mm as the right ceiling height for a normal family sauna and suggests going higher only with more than two bench levels.
Head clearance: upper bench to ceiling
This is the single most important bench dimension. Too much space and the bather sits below the best heat; too little and they cannot sit up comfortably.
| Source | Upper bench to ceiling | Notes |
|---|---|---|
| Harvia (bench guidance) | About 1,100–1,200 mm | “Less will suffice” for shorter bathers |
| Harvia (Cilindro heater manual) | No more than 1,200 mm | A model manual; other Harvia models have their own figures |
| Finnish Sauna Society, Sauna magazine (2023) | 1,000–1,200 mm | General Finnish guidance |
| Saunologia.fi | 1,000–1,200 mm | Finnish specialist guidance |
A worked example using Harvia’s figures: Harvia’s standard Formula bench set puts the upper bench at 900 mm and the lower bench at 450 mm from the floor. In a room with a 2,100 mm ceiling, that leaves 1,200 mm above the upper bench, at the top of Harvia’s recommended range. In a taller room, the benches have to rise with the ceiling, or the room needs another tier.
Why this matters: a generous ceiling looks luxurious on a drawing, but every extra 100 mm of height above the upper bench is air the heater has to warm and that the bather never feels. Ceilings are best set from the bench, not the other way round. See planning a home sauna for room sizes.
Depth, length, steps and layouts
Sources agree on the general shape of a good bench but publish slightly different numbers. None of them is a standard; they are ranges to design within.
| Dimension | Harvia | Finnish sources | Notes |
|---|---|---|---|
| Upper bench depth | At least 500 mm; 600 mm or more to lie down or lift your feet | About 450–600 mm for sitting (Saunologia); 600 mm (Finnish Sauna Society seat allowance) | Deeper benches suit lying and relaxed sitting |
| Length per seated adult | About 600 mm, “a good rule of thumb” | About 600 mm | Capacity comes from bench length, not floor area |
| Length to lie down | — | About 1,800–2,000 mm with legs extended (Saunologia) | Finnish Sauna Society: private-sauna benches typically 1,800–2,400 mm |
| Upper to lower bench | Standard Formula set: upper 900 mm, lower 450 mm (a 450 mm rise) | About 400–450 mm between bench and foot bench | Harvia suggests splitting the lower bench into 350 mm steps for easier access |
| Step riser | 350 mm | 300–350 mm (Saunologia) | Consistent risers are easier and safer to climb |
| Step tread | — | 250–350 mm (Saunologia) | Foot area at least about 300 mm wide |
| Room width with benches on two opposite walls | At least 2,200 mm; 2,500 mm for more legroom | — | Harvia figure |
| Bench board thickness | — | — | One Scandinavian heater maker specifies at least 22 mm for bench boards |
Common layouts
| Layout | Suits | Points to consider |
|---|---|---|
| Single wall, two tiers | Compact home saunas for one to four people | Simple and efficient; the heater usually sits on an adjacent wall or near the door |
| L-shaped | Larger home saunas; rooms where someone wants to lie down while others sit | More seats in the same room; Harvia’s standard bench sets include an L-form. Keep both arms of the L at the same height relationship to the heater |
| Opposite walls | Wider rooms, groups | Harvia asks for at least 2,200 mm between walls; the heater must not end up under or between benches without its full clearances |
| Three tiers | Taller rooms, commercial saunas, larger groups | Gives a choice of heat levels; needs a taller ceiling and careful step design for safe climbing |
Whatever the layout, benches do not go over the heater. Some manufacturers state this outright, and every heater has its own published safety distances to benches, which a guard rail must respect. Some tower heaters can be set into a bench using a flange the manufacturer supplies for that model; that is a model-specific option, not a general one. See sauna heaters and stones for heater types.
Room proportion and comfort
A sauna that feels right is usually compact and tall enough for the benches, not large. A few principles follow from the heat layers:
- Width follows the benches. A single bench wall needs only bench depth plus room to stand and move. Benches on two walls need Harvia’s 2,200 mm minimum or more.
- Height follows the upper bench. Upper bench height plus about 1,000 to 1,200 mm of head clearance sets the ceiling.
- The heater follows the volume. A bigger room needs a bigger heater and takes longer to heat. Glass and masonry add to the heater size because they absorb or lose heat faster than an insulated timber wall.
- Circulation space matters. Allow room to step up safely, to reach the heater’s stones with a ladle, and for the door to open outward without clashing with a bench.
Why this matters: most of the comfort problems people describe in saunas (cold feet, a hot head, a room that takes too long to heat) come back to proportion: too much height, benches too low or a heater that does not suit the room.
Bench timber versus wall timber
A wall is touched occasionally. A bench is sat and lain on, with bare skin, for minutes at a time. That is why bench timber is chosen to a stricter standard.
| Property | Why it matters on a bench | What to look for |
|---|---|---|
| Density | Denser timber conducts heat to skin faster, so it feels hotter at the same air temperature. US Forest Products Laboratory data show thermal conductivity rising with density and moisture | Low-density species: western red cedar, aspen, alder, abachi. Dense hardwoods are unsuitable for hot-room benches |
| Knots | Knots are denser than the surrounding wood and usually contain more resin, so they become hot spots and possible bleed points. A Harvia manual warns that knots on seating “can become very hot” | Clear grades for anything skin touches |
| Resin | Resin softens and can bleed at sauna temperatures | Non-resinous species, or resin-free thermally modified timber |
| Grain direction | Wood conducts heat roughly twice as fast along the grain as across it, so exposed end grain feels warmer and absorbs water fastest | Face grain on seating surfaces; seal or detail exposed bench ends as the timber supplier advises |
| Splinters and smoothness | Soft timbers can splinter where the grain runs out at an edge | Well-machined, smooth, rounded edges; well-sanded surfaces |
| Stability | Benches go through daily cycles of heat, sweat and drying | Kiln-dried, stable timber; supported spans |
Walls and ceilings can take knotty grades if the look appeals. Benches, backrests and headrests should be clear. Our guide to choosing sauna timber compares the species in more depth.
What we use for benches
Western red cedar is our principal timber, and we use clear grades wherever skin touches, including benches, backrests and headrests. Western red cedar is among the lowest-density common sauna timbers, so a clear board feels comfortable to sit on. We sometimes use Canadian hemlock where a paler, almost scent-free room is wanted. Read more in our guides to western red cedar and Canadian hemlock.
Clear grades
Grade names vary by producer and product line. For western red cedar, the Western Red Cedar Lumber Association describes clear grades (such as Clear Heart and A Clear) that are knot-free or very nearly so, and knotty grades with sound, tight knots. Whatever the names, the grade should be specified on the order for every bench component.
Bench construction details
These are widely recommended practices drawn from manufacturer instructions and Finnish guidance. Exact methods vary between bench systems and timber suppliers.
- Fasten from below. Harvia’s guidance is to fix benches from underneath, so no metal is exposed where skin touches. Its standard bench sets use locking pieces screwed under the bench and bench surrounds fixed from behind. Why this matters: metal conducts heat hundreds of times faster than timber, so an exposed screw head can burn.
- Use non-staining fixings. The Western Red Cedar Lumber Association recommends stainless steel, hot-dip galvanised or aluminium fasteners in cedar. Why this matters: iron reacts with cedar’s natural extractives and leaves dark stains.
- Round the edges. A radiused front edge is more comfortable behind the knees, is less likely to splinter, and is less likely to split, which matters especially with more brittle thermally modified timber.
- Plan the structure before lining. Harvia’s planning instructions show reinforcements inside the wall for bench supports and a horizontal batten behind the lining for backrests. Bench loads go into the framing, not the lining boards. Why this matters: a bench carries several adults; panelling alone is not made to hold it.
- Support free ends. A bench that does not span between two walls needs an end support. Longer benches need intermediate supports at the spacing the bench system specifies.
- Let air move under and behind. Slatted seats, gaps at bench ends and supports that hold benches slightly off the wall let the timber dry after each session. One timber maker’s bench modules, for example, call for a 4 to 5 mm gap between bench ends and walls. Why this matters: timber that stays damp marks, moves and deteriorates sooner.
- Make sections removable. Benches that lift off their supports, and boards that can be replaced, make cleaning, drying and repairs straightforward. Avoid sealed voids under benches that can never be reached.
- Backrests with an air gap. Slatted backrests fixed to the wall above the bench, with air behind, make the upper bench comfortable to lean on without trapping moisture against the wall. In hybrid saunas, infrared emitters are often set into backrests, which changes how they are built.
- Light low, not overhead. A Harvia manual notes that lights last longer placed low and away from the heater, and that under benches is an ideal position, which also gives a soft, glare-free light.
Finishes deserve a separate decision. Varnish and lacquer do not belong in a hot room. Harvia offers a paraffin oil for benches, and sources disagree on whether to treat walls at all, so follow the timber supplier’s and heater manufacturer’s instructions. Our sauna care guide covers cleaning and upkeep.
Glass and benches
Glass changes both the heat and the bench layout. Glass loses heat faster than an insulated timber wall, so the heater must be sized up: Harvia adds about 1.2 m³ to the room volume for every square metre of glass, and other manufacturers use different allowances. Glass also gets hot; one European heater maker limits touchable outer glass surfaces to 76 °C and calls for guards where needed. Benches facing a glass wall give the best view, but they should not leave bathers leaning against hot glass. See how a sauna heats for the sizing effect and planning a home sauna for glass doors and fronts.
Accessibility and commercial rooms
Commercial saunas have to work for many people of different ages and abilities, and they work harder than home rooms.
| Home sauna | Commercial sauna | |
|---|---|---|
| Steps | Two tiers are usually enough; a split lower step helps older users | Even, consistent risers and treads across all tiers; consider three tiers for choice of heat |
| Heater guard | Required as the heater’s manual specifies | Required as the manual specifies; sturdier detailing for heavy use. Guard dimensions are model-specific, and some makers limit the guard to no higher than the top of the heater |
| Bench timber and wear | Clear, low-density timber | Clear timber with a plan for replacing worn boards; more frequent cleaning |
| Cleaning | Bench towels and regular cleaning | Harvia’s North American manuals suggest scrubbing benches about weekly in commercial saunas; towels for every bather |
| Inspection | Periodic check of benches and supports | Some manufacturers ask for benches and supporting structures to be inspected yearly |
| Access | As the owner needs | Determined for the building by the access consultant and certifier |
Australia has no sauna-specific accessibility standard that we have found. Where the National Construction Code’s access provisions and AS 1428.1 apply to a building, whether and how they reach a sauna room is for the access consultant and building certifier to decide. Harvia suggests splitting the lower bench into two shallower steps to make climbing easier, which is a simple improvement in any room. Our guide to commercial saunas and steam rooms covers operator requirements more broadly.
Heater clearances and guards are model-specific
Every heater has its own published safety distances to benches, walls and ceiling, its own minimum ceiling height and, where needed, its own guard-rail arrangement. Never take a clearance from another heater or from a general guide. The installation manual for the selected model governs.
Bringing it together
Benches, heater and ceiling are best designed together, because each sets the others. The upper bench relates to the ceiling, the foot bench to the heater’s stone line, and the layout to the number of people and how they want to use the room. Clear timber then goes on every surface skin touches.
How we approach it
If you are planning a sauna, send us the room’s dimensions, the ceiling height and how many people will use it at once. We will explain how the benches and heater could work in that space. Contact us to start.