How to Build a Hammam: Stone, Heating and Drainage

Sauna Dekor has manufactured custom-built hammams, Turkish baths, saunas and complete wet areas since 1987 and is now in its 40th year. What follows is the build sequence we use, written for architects, spa consultants and owners who have a room on a drawing and not yet a stone schedule.

• What makes a room a hammam
• How to build a hammam, stage by stage
• How big the göbek taşı has to be
• Which marble to build from
• How the stone is heated
• What size steam generator it needs
• Draining and tanking the floor
• How much ventilation it needs
• What decides the cost
• What belongs on the drawing
• Who builds it, and what we do not do
• Frequently asked questions
• Sources

Heated stone, not heated air. A hammam runs at 40–45 °C with high humidity, the same air temperature as a commercial steam room, but every surface is warm marble and the radiant heat does the work. That is why 40 minutes in a hammam is comfortable where 15 minutes in a steam cabin is usually enough.

Three elements carry that logic, and the first one sets the whole plan.

The göbek taşı — the heated central platform — is a raised slab in the middle of the space, warm enough to lie on, where washing and scrubbing happen. It makes the hammam a social room rather than a cabin: people stay on it for a long time at a moderate temperature, which is a different brief from a cabin designed for short, hot sessions.

The kurnas are the marble basins set against the walls, each with hot and cold taps and no waste. They are filled, and water is poured over the body with a bowl. A hammam is a pouring bath, not a shower, and that single fact changes the drainage design more than anything else in the room.

The shell is stone on every surface under a domed or vaulted ceiling. The form is inherited rather than invented: Roman bath buildings heated their floors and walls from a furnace through a hypocaust, and the Ottoman hammam kept both the heated floor and the sequence of rooms around it. The room English speakers call a Turkish bath is this one. The Moroccan bath is the same physics with a different ritual and a different room sequence, and a modern hammam keeps the heated stone while dropping the historic dome geometry.

In seven stages, and the order is not negotiable: shell and structure, tanking and falls, heating circuits and screed, stone, steam plant, ventilation, commissioning. Stage 2 cannot be revisited once marble is down, which is why a hammam that leaks is almost always a hammam whose stone was ordered too early.

1. Shell and structure. Internal dimensions, ceiling geometry, and the finished dead load issued to the structural engineer. A marble platform is a structural item, not a fit-out item.
2. Tanking and falls. A continuous vapour barrier on the warm side of the insulation, a bonded waterproofing membrane, and floor falls formed in the screed across the whole floor.
3. Heating circuits and screed. Hydronic pipe or electric cable under the platform and the seating, zoned separately, with sensors in the slab and manifolds reachable from outside the room.
4. Stone. Cut to a schedule that states thickness, finish and vein direction per element, and set only after the screed has fully dried out and stopped moving.
5. Steam plant. Generator sized against cold stone, injection point low and guarded, water treatment on its own supply.
6. Ventilation. Extract that runs after closing rather than during use, ducted to outside.
7. Commissioning. Surface temperatures measured at the platform and the seating, pre-heat and steam sequences set, drying overrun timed, and the room handed over with those settings written down.

Two of these stages are invisible on handover day — tanking and heating — and both are the most expensive things on the list to retrofit. That is the whole argument for taking them in order. The tanking layer carries the same failure pattern as a steam room vapor barrier: it goes at the crossings, not in the field.

Start from the body, not from the room. One person lying flat needs about 2,000 × 700 mm of usable stone, and a therapist working alongside needs 800 mm of clear floor on at least one long side. A two-person platform is therefore around 2,200 × 1,600 mm, which wants a room of roughly 16–20 m².

The working figures we build to:

• Two-person platform: around 2,200 × 1,600 mm, in a room of about 16–20 m²
• Four-person platform: around 2,400 × 2,400 mm, in a room of about 25–30 m²
• Platform height: 400–450 mm — lower is hard to get off, higher makes a therapist work with their arms up
• Clear floor: 800 mm minimum on working sides, 600 mm elsewhere
• Kurna spacing: 1,200 mm centres, so two people can sit and pour without colliding
• Ceiling height: 2,600 mm minimum at the springing of the dome, or the room feels like a corridor once the steam is up

A platform bigger than the room can carry is the error we are most often asked to correct. It looks generous on a plan and leaves nowhere to stand, and because the slab is heated, the wasted stone is also wasted energy every single day the room is open.

A tight, low-absorption marble, cut with the vein running along the length of each piece, at 30–50 mm thickness on the platform. Marble here is a thermal and structural component rather than a finish: it is heated, wetted, cooled and heated again every day for years, and three properties matter far more than colour.

Porosity. An absorbent stone takes on water and then takes on whatever is dissolved in it. Oils and soap residue stain porous marble permanently, and no sealant survives an indefinite wet cycle. Water absorption is a measured property with a published test method, and the Natural Stone Institute is the clearest source for how those figures are produced and read. We specify low-absorption stone for the platform and the seating and accept a wider range on upper wall linings, where nobody sits and nothing pools.

Vein direction. Heavily veined marble is weaker along the vein. On a heated slab that is knelt on and leaned against, the vein must run along the length of the piece rather than across the span. This is a cutting instruction, and it belongs on the drawing rather than in a phone call to the yard on the morning of the cut.

Thickness and weight. Thicker stone stores more heat and holds surface temperature steadier between guests, but comes up more slowly in the morning and adds real dead load. A four-person platform in 50 mm marble is a structural item, and the finished weight has to reach the structural engineer early rather than at the point of ordering.

Through circuits underneath it, controlled to a surface temperature rather than to an air temperature. The usable target on the platform is 40–42 °C, comfortable against bare skin for 30 minutes or more. Above roughly 45 °C the stone stops being pleasant and starts being endured, and wall seating is normally run two or three degrees cooler.

Two systems do this, and the building usually decides which one.

Hydronic circuits in a screed bed under the slab give an even, slow, stable heat and suit a property that already has a low-temperature water circuit. They need a manifold with accessible isolation valves, and that manifold has to be planned into an adjacent service space rather than buried under stone.

Electric mats or cables install more simply and respond more quickly, which suits a private hammam used two or three times a week rather than a commercial floor running sixteen hours a day. The trade is running cost and the fact that a failed cable under a bonded slab is not a repair, it is a rebuild.

Whichever is chosen, three details are not negotiable. The temperature sensor sits in the slab and not in the air, because air temperature says nothing about how the stone feels underneath a wet body. The platform and the seating are zoned separately because they run at different setpoints and warm up at different rates. And every joint, junction box and manifold stays reachable without lifting marble — the single detail that separates a room we can service in an hour from one that needs a stonemason.

Roughly 1.0–1.4 kg of steam per hour per cubic metre, against 0.5–0.6 kg/h/m³ for an insulated acrylic cabin of the same size. A 12 m³ marble hammam therefore needs around 14 kg/h where an acrylic cabin of identical volume needs about 7 kg/h. Same volume, roughly double the machine.

The reason is condensation. Cold stone is a large, high-mass surface that condenses steam continuously, so the generator has to replace what the walls take on top of filling the room. A machine sized from a volume table alone will never hold a marble room, and this is the most common specification failure we see on hammam projects — more common than undersized drainage, and far more expensive to correct, because the plant room is usually finished by the time anyone notices.

Two operating rules follow from the same physics. Bring the stone up to temperature before the steam, or the first hour of every day is spent condensing onto cold marble instead of filling the room. And place the injection point low, away from any seat and away from the platform, with a guard, because steam leaves the nozzle far hotter than the room it is entering.

We do not manufacture steam generators. We size, supply, install and commission them; the machine itself is built by a specialist and carries that manufacturer’s certification, not ours. The steam generator page sets out the output ranges we specify and the water treatment that goes with them.

With falls formed across the entire floor rather than towards one position, and gullies sized on open grate area rather than nominal pipe diameter. We aim for a fall of roughly 1:50 and no point on the floor more than 2 m from a gully. A hammam is a pouring bath, not a shower.

Bowls of water come off every kurna and off the platform, so every square metre of floor needs somewhere for that water to go within a metre or two of where it lands. A single central gully, which is what a shower room drawing usually offers, leaves half the floor wet.

The build-up underneath matters as much as the fall:

• Full tanking, with a continuous vapour barrier on the warm side of the insulation. There is no partial version. Vapour finds any discontinuity — a pipe penetration, a fixing, an unsealed lap — and condenses inside the construction, where the damage stays invisible until it is expensive. Bonded waterproofing membranes below tile and stone are covered by published standards, and the Tile Council of North America maintains the North American reference for them.
• Trapped, accessible gullies that can be cleaned without lifting stone. A trap that needs a marble slab cut out is a trap that never gets cleaned.
• A domed, vaulted or sloped ceiling with a fall of at least about 1:10, so condensate runs to the walls instead of dripping onto the people below. A flat ceiling in a saturated room is a design error, not a style choice.
• A threshold and a dry-side transition that keeps poured water inside the room. Falls stop at the door only if someone drew them stopping there.

Where a hammam sits inside a larger thermal suite with pools and water features around it, the same discipline extends to the water systems: the UK Health and Safety Executive’s guidance on spa-pool systems (HSG282) is the clearest published statement of an operator’s duty of care on the water side, and it is worth reading at design stage rather than at handover.

Enough to dry the room after closing, and almost none during use. Extract running while the room is occupied pulls out steam that the generator has just paid to produce, so the useful arrangement is a timed drying overrun of 30–60 minutes after the last session, ducted to outside rather than into a ceiling void.

Three things follow. The extract point goes high, where the wettest air sits, and the make-up air comes in low and dry. The duct is insulated for its whole run, because an uninsulated duct in a cold void condenses inside itself and drips back into the room. And the drying cycle is tied to the heating control, not to a separate switch somebody forgets, so the marble is still warm while the air is being changed — a warm room dries in a fraction of the time a cold one does.

A room that never dries becomes a maintenance problem inside a year: grout darkens, joints hold residue, and guests read stale air as a dirty room long before anything is visibly wrong. This is the cheapest stage on the whole list and the one most often value-engineered out.

Five variables, in descending order of impact: the stone specification, the platform size, the heating system, the build-up behind the finish, and the room’s position in the building. We do not publish prices, because a hammam is not a catalogue item — but this ranking has been stable across the projects we have delivered in 41+ countries.

1. Stone. Type, thickness, finish, and the amount of carved or inlaid work. Carving hours move a budget further than square metres do, and two rooms of identical area can differ by a factor that has nothing to do with their size.
2. Platform size. A four-person göbek taşı is not twice a two-person one. It is a heavier slab, more support beneath it, a larger heating zone, and a bigger room around it.
3. Heating. Hydronic with a manifold and controls against electric mats; the number of zones; and whether a low-temperature circuit already exists in the building or has to be created for one room.
4. Build-up. Tanking, insulation, screed falls and drainage. Invisible on handover day, and the most expensive thing on the list to retrofit.
5. Position. A basement room with a plant space next door and a floor that can be raised is a different job from a room on level six with 90 mm of build-up available and a lift booking.

The honest short answer to “what does a hammam cost” is that the stone schedule and the floor build-up decide it, and both are knowable from a plan and a section long before anyone quotes. If you want a useful number early, get those two drawn first.

Seven lines. A specification that says “hammam, 22 m², marble” tells a manufacturer almost nothing, and the gap gets filled with assumptions that surface later as variations. These seven turn a mood into a buildable room:

1. Platform dimensions and height, with the clear floor around it dimensioned
2. Target surface temperature at the platform and at the seating, stated separately
3. Heating system, number of zones, and where the manifold or junction box is reached from
4. Stone type, water absorption, thickness per element, and vein direction
5. Finished dead load, issued to the structural engineer
6. Steam output in kg/h, injection position, and the pre-heat sequence
7. Tanking specification, floor falls, open grate area, ceiling fall and the drying regime

Every one of these is answerable from a plan and a section. None of them needs a supplier to be chosen first, which is exactly why they should be settled before one is.

Sauna Dekor designs, manufactures, installs and commissions the room. The stone is cut and finished in our own facility in Istanbul, the tanking and the heating are ours, and one team hands the room over. We are a company of 19 people, delivering to 41+ countries, and our quality system is certified to TS EN ISO 9001:2015.

What we do not do, stated plainly:

• We do not manufacture steam generators, heaters or control gear. We specify, supply, install and commission them, and their approvals belong to their manufacturers rather than to us.
• We do not hold CE, EN 60335, TÜV Rheinland, GS, GREENGUARD or FSC marks — each of those belongs to the equipment or material manufacturer we buy it from, and is issued in that manufacturer’s name rather than in ours.
• We do not keep installation crews in every market. Outside our own teams, installation is carried out by a local contractor working to our drawings and under our commissioning.
• We do not sell hammams from a catalogue, and we do not publish prices for rooms we have not drawn.

Delivered hammam work includes a diplomatic members’ club in Doha, a five-star hotel in Sulaymaniyah, a community villa development in Riyadh in 2024, and private villas in Emirates Hills and in Bodrum. Hotel references include Hilton Istanbul Maslak in 2017 and Ritz-Carlton Istanbul in 2013. Developer and contractor clients include Emirates Engineering.

One delivery window we can state exactly is not a hammam but sits next to one: a 6 m² snow grotto handed over to a private villa in October 2025 ran fourteen weeks from order. A hammam of 16–20 m² runs longer, because stone cutting and finishing, not installation, is the long pole.

If you have a room and a plan but no stone schedule yet, send the internal dimensions, the ceiling height and the floor build-up available to you, and contact our team — that is enough for a first layout.

The room air in a hammam is kept at 40–50 °C with high humidity, which is milder than a sauna. Heat comes from the floor, walls and the central heated stone platform, and steam is added to keep the air moist. Marble or stone surfaces, a domed or sloped ceiling and good drainage complete the room.