The Gym Sauna: What Commercial Duty Actually Means for Sauna and Steam in a Fitness Facility

A gym sauna is sized from peak use, not from the floor plan. Count the members you expect in the busiest hour, allow bench length per person, then add the heater guard zone and a clear door swing. We draw the room with the heater, ventilation and power route before anything is ordered.

Sauna Dekor Spa Solutions engineering team, Istanbul · reviewed 30 September 2026 · project and press enquiries: Alican Aykaç, Managing Partner

Budget roughly 1 kW of heater per cubic metre of cabin, plus about 1.2 kW per square metre of glass, and allow 0.6–0.8 m² of bench per person. Get those five decisions right at drawing stage and the room lasts fifteen years; get them wrong and it is a maintenance ticket by month eight.

Sauna Dekor is a sauna, steam room and hammam manufacturer and turnkey wet-area contractor based in İkitelli OSB, Başakşehir, Istanbul, Türkiye. We have been designing, manufacturing and installing thermal rooms since 1987 — this is our fortieth year — and we have delivered in 41+ countries, with our heaviest concentration of commercial work in the Gulf: Dubai, Abu Dhabi, Doha and Riyadh. Our own certification is TS EN ISO 9001:2015 quality management, covering sauna and spa product manufacturing and after-sales service. The equipment we install carries CE / EN 60335, TÜV, GS and GREENGUARD certification from its own manufacturers — EOS, Sentiotec and Condair among them.

We write this because the gym sauna is the single most frequently under-specified room in a fitness facility. It is drawn late, valued out early, ordered as a catalogue item, and then it becomes the amenity members complain about most. Almost every failure we are called to inspect traces back to the same root cause: a domestic-grade room was installed into a commercial duty cycle. Our fitness and sport centre construction work exists to stop exactly that.

A residential sauna is switched on, used for thirty to sixty minutes, and switched off. It might run 250 hours a year. A gym sauna in a busy club opens with the facility and closes with it. At twelve hours a day, six and a half days a week, that is roughly 4,000 hours a year — sixteen times the domestic figure. Everything downstream follows from that ratio.

• The heater is not cycling to temperature and then resting. It is holding a setpoint against a door that opens every ninety seconds.
• The contactor in the control gear switches on a duty cycle its domestic equivalent was never rated for.
• The timber takes wet feet, sun cream, chlorinated air from an adjacent pool hall, and abrasive cleaning chemicals, every day.
• The floor receives water continuously and has to move it somewhere.
• The ventilation has to clear spent air from a room that never gets an eight-hour break to dry out passively.

This is why “commercial duty” is a specification category and not a marketing adjective. When a tender document says commercial sauna, the meaning that matters is continuous-duty heater, industrial contactor, serviceable control gear, replaceable bench modules and a tanked substrate. Our commercial sauna specification guide sets the full tender language out clause by clause; what follows here is the fitness-facility version of it.

The first question we are asked about a gym sauna is almost always about kilowatts, and it is the wrong first question. Start with occupancy.

Allow 0.6–0.8 m² of bench per person, which in practice is two seated places per linear metre of bench. A 6 m² cabin with an L-shaped two-tier bench run seats eight to ten comfortably and twelve at squeeze. As a planning rule for a members’ club, we size the thermal rooms to roughly 1 % of peak concurrent occupancy per seat — a facility with 1,200 members and a 180-person peak wants somewhere around 10–14 thermal seats split across sauna and steam, not one four-person box.

Three dimensional constraints decide whether the room actually works:

• Ceiling height 2,100–2,300 mm internal. Higher wastes energy heating air nobody sits in; lower makes the top bench unusable.
• Top bench 1,050–1,100 mm below the finished ceiling. This is the seat that people actually want, and it is the one most often lost to a services zone that arrived after the sauna was drawn.
• Bench depth 500 mm minimum for sitting, 600 mm if anyone is expected to lie down. In commercial rooms we default to 600 on the top tier and 400 on the step tier.

In hotel and club work these numbers get squeezed by the pool hall next door, which is why we prefer to set the thermal suite footprint before the wet-area layout is frozen. Our hotel spa design guide covers the wider zoning logic; the gym version is simpler, because the sauna is usually a single volume off the changing rooms rather than a circuit.

Once the volume is fixed, the heater follows arithmetic rather than judgement.

Roughly 1 kW per cubic metre of internal cabin volume, then add about 1.2 kW per square metre of glass and about 1 kW per square metre of uninsulated stone or masonry. A 9 m³ cabin with a standard glass door lands at 9 kW. The same cabin with a full glass front — which is what most modern gyms want, because a visible sauna is a used sauna — lands at 12–15 kW. That is not a rounding error, and it is the number most commonly missed when a design goes from concept sketch to procurement.

For commercial duty we then change three things a domestic package would not have:

1. A continuous-duty heater from the commercial range, not the domestic range at the same kW. The kilowatt figure is the same; the element sheathing, the stone volume and the thermal cut-out arrangement are not. Heater manufacturers publish separate commercial series for this reason.
2. A separate control unit outside the cabin, with a timed enable, a maximum session limiter and a facility-level lock-off. Members should not be able to change the setpoint. Staff should be able to shut the room down from the reception desk.
3. A volt-free contact to the building management system. Remote enable, scheduling and alarm reporting. Specify it at tender — retrofitting BMS integration into a commissioned sauna is disproportionately expensive.

Setpoint for a commercial Finnish cabin is 80–90 °C at 10–20 % relative humidity. Fittings inside the cabin need IP54 as a minimum, with luminaire drivers sitting outside the hot zone; anything in a washed-down or steam environment goes to IP65. If the facility wants an infrared cabin instead, the electrical and ventilation logic is different again — types of sauna heaters sets out where each one belongs.

When a gym sauna will not hold temperature, the reflex is to buy a bigger heater. It is almost always the wrong purchase. The room needs six to eight air changes an hour, with supply low beside or under the heater and extract high on the diagonally opposite wall, ducted to outside. A 9 m³ cabin therefore needs 54–72 m³ of air an hour moving through it.

Two commercial-specific points sit on top of that general rule:

• The extract must not discharge into a ceiling void, plant room or changing area. In a gym this is the single most common shortcut, and it relocates the moisture problem into the building fabric rather than solving it.
• Mechanical extract earns its place here in a way it does not domestically. A domestic cabin gets eight idle hours a night to dry passively. A gym sauna gets a scheduled 60–120 minute drying overrun after close, door held ajar, extract running — and that overrun is what determines whether the room smells right in year three.

We have written the full engineering case separately in sauna ventilation, including why the gap under the door is pressure relief and not ventilation. For a fitness facility, treat that article as the mandatory reading and this section as the commercial addendum.

Timber selection for a gym sauna is a durability decision, not an aesthetic one. The bench and backrest surfaces take skin contact at 85 °C, so they need a low-density, low-conductivity species that does not scorch: ayous, aspen or alder. Wall and ceiling linings are kiln-dried pine.

What separates a fifteen-year commercial room from a five-year one is not the species, it is the detailing:

• Bench modules that lift out. They will be replaced once or twice in the life of the room. If they are fixed in place, that becomes a shutdown rather than an overnight job.
• Concealed fixings throughout. Any metal reachable by skin at 85 °C is a burn incident waiting for a date.
• No varnish, no sealant, no oil on any surface a member touches. Untreated timber in the hot zone. Treatments in a sauna do not last, and they fail by going tacky and yellow.
• A gap between bench and wall. Air needs to move behind the seating, and cleaning staff need to reach the floor.

Where a gym sauna sits next to a chlorinated pool hall, the ventilation strategy has to keep chloramine-laden air out of the cabin — it is aggressive to both timber and heater elements. That is a coordination decision between the pool AHU and the sauna extract, made at MEP stage, not a product selection. The cabins we build for this environment are detailed in our custom sauna manufacturing range.

If the facility has the space and the budget for one thermal room, it should almost always be a sauna: lower running cost, simpler build-up, faster to bring back after a fault, and better understood by a general membership. If it has room for two, the second should be a steam room, because it serves a materially different user and a different session length.

The two rooms are not variations of each other. A steam room is a design condition of 40–50 °C at close to 100 % relative humidity, which means a fully tanked enclosure, a graded and drained floor, a seamless mosaic or acrylic lining, a generator with its own water treatment and drain-down cycle, and a vapour-tight envelope. It is a wet-construction trade. A sauna is a dry-construction trade. Putting them on the same page of a bill of quantities is how facilities end up with a steam room detailed like a shower. Our sauna versus steam room comparison covers the user-side difference; the build-side difference is bigger.

A third room worth planning for even if it is deferred: a cold plunge pool. Contrast bathing is now the reason a large share of members use the thermal suite at all, and the plunge is the element that most often has no space reserved for it because nobody drew the chiller, the filtration skid or the drain. Reserving 4 m² and a plant allowance costs nothing at drawing stage. For what members are actually doing with the sequence, see sauna after workout and sauna and recovery.

A gym sauna cabin is a joinery product delivered onto a prepared opening. Nearly every dispute we see between a main contractor and a sauna supplier is about the condition of that opening. The builder’s-work items are:

• A level, tanked, graded floor with a drain. Even a dry sauna gets washed. Tile the floor and grade it to a gully — never leave a sauna floor flat.
• Structural clearance for the finished cabin, including the ventilation route, which needs deciding before the ceiling closes.
• A dedicated electrical supply, correctly rated and terminated at the control position. A 15 kW heater is a three-phase load; it is not a socket outlet.
• Cold water and a drain to the steam generator position, if there is a steam room.
• An agreed sequence. The cabin goes in after wet trades and before final floor finishes.

We normally take these five items as a coordination package with the main contractor rather than a list handed over at site — which is what we mean when we describe ourselves as a spa subcontractor rather than an equipment supplier. The broader scope is on our commercial spa contracting page.

Three things change when the facility is in Dubai, Abu Dhabi, Doha or Riyadh, and none of them are about the sauna itself.

Make-up air is hot. Summer air above 45 °C drawn straight into a cabin changes the heater duty and the humidity load the room has to shed — noticeably so on the coast, where dew point is high. On commercial projects we take the sauna supply from the conditioned spa envelope and duct only the extract to atmosphere.

There is a permitting layer, and it is on the critical path. Extract routes crossing fire compartments need fire dampers and Civil Defence sign-off under the UAE Fire and Life Safety Code of Practice. The heater and fan load sits inside the DEWA connection application in Dubai, and its equivalent elsewhere. Neither is difficult; both are slow if they surface after the ceiling is closed.

Gender-separated provision is usually a programme requirement, not an option. In Saudi and Qatari facilities in particular, plan for duplicated thermal rooms from the first sketch. Two 6 m² cabins is a completely different footprint and plant load from one 12 m² cabin, and discovering it late is one of the more expensive ways to lose a spa floor.

We deliver into these markets from our Istanbul factory with local installation supervision. City-level detail is on our Dubai and Riyadh pages. Recent commercial work in this category includes a members’ club spa and fitness floor in Doha, a residential tower fitness and spa level in Baku, and hotel spa floors with integrated fitness in Istanbul.

A gym sauna is an operational asset, and the operator’s habits determine its lifespan more than the specification does.

• Daily: wipe benches with water and a pH-neutral cleaner. No solvents, no bleach, no scented products — they soak into untreated timber and stay there.
• Daily: run the drying overrun after close. This is the single highest-value maintenance habit in the building.
• Monthly: inspect and rotate the heater stones. Stones fracture; fractured stones pack down, restrict airflow through the element bed and shorten element life.
• Annually: replace the heater stones entirely, check the thermal cut-out, torque the contactor terminals, and inspect bench fixings.
• Every three to five years: light-sand the bench modules or replace them.

Our sauna maintenance guide has the full schedule. Hand it to the facility team at handover rather than filing it in the O&M manual, where nobody will find it.

Everything above, condensed into the lines we would expect to read in a gym sauna tender document.

• Occupancy: 0.6–0.8 m² bench per person; two seats per linear metre of bench.
• Geometry: 2,100–2,300 mm internal height; top bench 1,050–1,100 mm below ceiling; 600 mm top-tier bench depth.
• Heater: ~1 kW/m³, plus ~1.2 kW/m² of glass and ~1 kW/m² of uninsulated stone. Commercial-duty series, not domestic at the same kW.
• Controls: external control unit, timed enable, session limiter, staff lock-off, volt-free BMS contact.
• Conditions: 80–90 °C, 10–20 % RH. IP54 minimum inside the cabin, IP65 in wet areas.
• Ventilation: 6–8 air changes/hour, low supply beside the heater, high extract diagonally opposite, ducted to outside, 60–120 minute drying overrun.
• Timber: ayous, aspen or alder on contact surfaces; pine linings; concealed fixings; no coatings; lift-out bench modules.
• Substrate: tanked, graded, drained floor; dedicated correctly rated electrical supply; ventilation route agreed before ceiling closure.
• Gulf: supply from the conditioned envelope, fire dampers at compartment crossings, gender-separated provision planned from day one.

"Gym sauna" is a use case, not a room type, and the tender should name the room. A Finnish sauna with an EOS or Harvia continuous-duty stone heater is what most fitness clubs mean, and it is the only one of the four that carries the six-to-eight air-change requirement discussed above. A bio sauna runs cooler with an integrated evaporator and suits a recovery suite where members stay longer. An infrared sauna uses carbon or full-spectrum quartz emitters, draws far less power and fits a floor plate that cannot take a 9 kW heater and its ventilation. A hybrid sauna combines the Finnish and infrared modes in one cabin where a club has one room and two member populations, and a panoramic glass sauna puts the cabin on display in the studio floor rather than behind a corridor door.

Cladding is specified by species and grade — ayous and pine, with aspen and alder on request — because a commercial duty cycle, not a domestic one, is what wears a bench out. Sauna Dekor manufactures these cabins in its own factory in İkitelli OSB, Istanbul, in business since 1987 and now in its fortieth year, and installs them for gyms, hotel spas and wellness centres in the UAE, Saudi Arabia, Qatar, Kuwait and Bahrain. Where a club pairs the cabin with contrast bathing, the plant and drainage interface is covered on our cold plunge pool page, and the full tender language is in the commercial sauna specification.

Sauna Dekor has designed, manufactured and installed saunas, steam rooms, hammams and thermal suites since 1987 — now in our fortieth year — in 41+ countries, from our factory in İkitelli OSB, Başakşehir, Istanbul. For fitness facilities we work either as a subcontractor to the main contractor or directly for the operator, and in both cases the useful conversation happens while the cabin is still a rectangle on a plan and the ventilation route is still a dotted line. Send us your thermal suite footprint, peak occupancy and services drawing and we will tell you what we would specify and what we would move.

Sources

• International Electrotechnical Commission. IEC 60335-2-53: Household and similar electrical appliances — Safety — Particular requirements for sauna heating appliances and infrared cabins. webstore.iec.ch
• ASHRAE. Standard 62.1 — Ventilation and Acceptable Indoor Air Quality. ashrae.org
• UAE Ministry of Interior, General Directorate of Civil Defence. UAE Fire and Life Safety Code of Practice. moi.gov.ae · u.ae fire safety
• Dubai Electricity and Water Authority. Regulations for Electrical Installations. dewa.gov.ae
• US Environmental Protection Agency. Mold Course, Chapter 2: Why and Where Mold Grows. epa.gov

In Saudi Arabia, our gym work includes Next Wellness Club in Al Khobar (2024), with sauna, steam and recovery zones; see gym recovery zones.