What Bathhouse Development Actually Requires

Bathhouse NYC expects a $120 million run rate by end of 2026. Bathhouse just raised $35 million for an eight-city expansion, and Sauna House is franchising the Nordic bathhouse format with data-backed unit economics. Entrepreneurs, hotel developers, fitness operators and nightclub owners all want to know how to build one.

A social wellness club is a hospitality operation built around heat, water, and humidity, and all three punish shortcuts in a building. The design decisions you make in the first 90 days of your project will determine whether you spend the next decade running a profitable business or fighting your own infrastructure.

Wet space costs far more than a commercial shell

The single biggest mistake first-time operators make is underestimating cost.

Per-square-foot figures for generic commercial construction are nearly useless for a social wellness club. Once a building has heat, water, and humidity, those figures stop applying. Wet areas, particularly hammams, steam rooms, and multiple pools, cost far more per square foot to build than a standard commercial shell, and that is before interior finishes.

Most of the cost is invisible to the guest: ventilation systems that move enormous volumes of air through saunas and steam rooms; filtration and sanitation systems rated for bather loads far higher than residential equipment can handle; waterproofing that protects the structure below you (and any electrical rooms or parking garages beneath your slab); drainage capacity for the waste water you produce, which may exceed what you can pump out of the building in real time; and electrical supply upgrades that can cost more than the equipment they power.

One of the less obvious cost drivers is the gas-versus-electricity decision. If the incoming electrical supply to your building cannot support the load your thermal features require, the cost of upgrading that supply can be prohibitive, both in dollars and in time. In those cases, gas becomes a serious alternative for heating, not because it is inherently better, but because the electrical upgrade alone might blow your budget or your timeline.

The GWI Guide to Hydrothermal Spa & Wellness Development Standards, a detailed reference document for this space, devotes hundreds of pages to design and material considerations that most first-time operators have never encountered.

There is also the Costco sauna trap: prospective operators who search online and find residential saunas for $3,500 and hot tubs for the same price, then assume they can outfit a commercial facility for $25,000. Residential products cannot be used in a public facility. Operators routinely get sticker shock when they learn the difference between consumer-grade and commercial-grade equipment.

Your building starts in the mechanical room

Start with the engine room, not the guest experience. Mechanical space allocation, the rooms that house your pool filtration, steam generators, HVAC equipment, water heaters, and electrical panels, determines what your guest experience can be.

One thermal specialist described a project where the concept called for 13 pools and five private wet spa suites, but the architectural plans allocated enough mechanical space for just three pools. Worse, all the mechanical space was in a single location, 150 feet from the nearest steam room. Steam pipes cannot run that distance effectively. The entire concept had to be reworked after the thermal team was brought in, costing months and significant redesign fees that could have been avoided if the mechanical space had been planned first.

This pattern repeats. Architects and interior designers create beautiful concepts, investors approve them, and then the people who actually understand thermal systems arrive and explain that three treatment rooms need to become a mechanical room, that the profit projections need to be revised downward, and that the floor plan everyone loved is, as one practitioner put it, “really pretty average” in the real world.

Bring your thermal and MEP (mechanical, electrical, plumbing) specialists in at the same time as your spa consultant and your architect, before the first floor plan is drawn. The later they arrive, the more expensive their involvement becomes, because every change at that point is a correction rather than a decision.

At minimum, the engine room needs air handling for every thermal room (saunas and steam rooms require dedicated ventilation with high air-change rates), pool filtration and sanitation for every body of water, steam generators within workable pipe distance of their steam rooms, hot water systems, waste water storage tanks (if your drain connections cannot handle your peak output), and electrical distribution panels. If your building sits above a parking garage, you may also need raised floors to route drainage without penetrating the structural slab, which adds ramps, stairs, and ADA-compliant access to your design.

Plan for one-third non-guest space

Every bathhouse development is a fight between revenue-generating space and the operational space that makes revenue possible. The ownership argument is always the same: minimize the non-revenue areas. The operational reality is equally consistent: if you do not allocate enough back-of-house space, your guest experience will suffer every single day you are open.

A reasonable planning target is roughly one-third non-guest space. That covers mechanical rooms, linen storage, cleaning supply closets, staff changing areas, maintenance access corridors, and laundry (if you process on-site). The laundry math alone is sobering: a high-volume urban bathhouse can cycle thousands of towels per day, and every one of those towels needs a clean path from storage to guest area to collection to washing and back again.

Linen logistics sound boring. Experienced spa strategists will tell you it is “not sexy, but it is 101.” If you cannot move clean linen from Point A to Point B during operating hours, you need enough storage to hold an entire day’s worth of dirty linen until it can be removed after closing. The number of spas and wellness facilities that open with insufficient storage space is, according to practitioners who audit these projects, remarkably high.

Equally important is the dual journey principle. You are designing for two completely separate circulation paths: the guest journey (your revenue engine) and the maintenance journey (your operational backbone). You do not want a technician wheeling a tool chest through the sauna to reach the mechanical room. You do not want cleaning staff carrying chemical containers through the relaxation lounge. Every back-of-house access point, every maintenance corridor, every service entrance needs to be planned so that operations can happen during business hours without disrupting the guest experience.

This is why experienced teams typically go through approximately 20 revisions of a floor plan before arriving at something that works. Each revision tests a different balance between guest capacity, back-of-house access, code compliance, mechanical adjacency, and the aesthetic vision. Budget for that time in your project schedule. Rushing the floor plan is one of the most expensive mistakes you can make, because every problem you miss will be discovered during construction or, worse, after opening.

Small details matter here too. Hose bibs (quick-connect water points) should be placed near floor drains throughout your facility so cleaning staff can hose down surfaces efficiently. Floor drains themselves need to be planned during site selection, not added later; if there is a parking garage or electrical room below your space, cutting drains into the slab may not be possible, requiring a raised floor that changes your entire vertical circulation plan.

Codes, chemistry, and the rules that change by county

If you are planning a social wellness club in the United States, there is no single code book you can carry from state to state. Building codes for pools, thermal facilities, and public bathing vary by county, city, and state. Some jurisdictions use the Model Aquatic Health Code. Some use the International Swimming Pool and Spa Code. Some, like Florida, use half of one and half of another plus their own state-specific additions. In practice, this means you need a code consultant or a thermal specialist who has worked in your specific jurisdiction, because assumptions that held in one city may be completely wrong 50 miles away.

Some examples of how codes diverge:

• Spa pool draining: New York City’s Health Code Article 165 requires spa pools to be drained and cleaned when needed, and at least once every two weeks. This has significant operational and water-cost implications.
• Changeroom requirements: The same New York City code requires a bather preparation facility, with lockers, showers and toilets, for each gender. That effectively doubles your changeroom, shower, and bathroom square footage. In Canada, many public facilities use universal changerooms with private change stalls.
• Minimum clearances: Pool surround clearances, ADA access requirements, and egress path widths all vary by jurisdiction and directly affect how many features you can fit in your space.

One veteran of US hydrothermal construction put it bluntly: the codes in most North American cities were written decades ago, when bathing was a completely different activity. The bather loads in a modern social wellness club, where hundreds of people may cycle through the water in a day, far exceed what those codes were designed to handle. Responsible operators design well beyond code minimums, because code compliance alone does not guarantee a clean, safe, or pleasant guest experience. If your guests cannot see their feet when standing in your pool, you have a problem that code compliance will not fix.

On water chemistry: there is no public pool in the United States that can legally operate without a chemical disinfectant, and in practice that usually means chlorine; the Model Aquatic Health Code also permits bromine. A “salt pool” is a chlorine pool. The salt (sodium chloride) is fed through a chlorine generator that converts it into chlorine. The delivery method is different; the chemistry is the same.

The “pool smell” that people associate with chlorine is not actually free chlorine. The smell comes from chloramines, which form when chlorine reacts with organic material: skin oils, deodorant, hair products, perfume, sweat. This is why pre-swim showers are a hygiene requirement. The more guests shower before entering the water, the less chloramine buildup, the less smell, and the less chemical your water systems need to add. Some European facilities mandate Speedo-style swimwear and bathing caps specifically to reduce the organic load entering the water, which in turn reduces the chemical treatment required.

Revenue hides in multi-use rooms

Avoid single-purpose rooms where you can. Every room that can only do one thing is a room that sits empty whenever that one thing is not happening.

The example that surfaces most often is the dedicated wet treatment room with a Vichy shower or Swiss shower permanently installed. Those services may have value, but the fixed equipment ties up the entire room. A better approach is designing the room so the equipment can be moved or concealed when not in use, freeing the space for other programming.

One example is a hammam designed for a hotel spa in Miami, roughly 24 feet in diameter and 20 feet tall. The spa director began using it for yoga, chanting, meditation, and sound bowl sessions. Because a hammam is a warm room (not a steam room), it creates a comfortable climate for all of these activities. An unexpected bonus: the domed architecture turned out to be acoustically extraordinary for chanting and singing. None of this was in the original design brief. It emerged because the room was large enough and flexible enough to support uses nobody had imagined.

The same logic applies to the Aufguss movement, which gives operators a way to generate revenue from thermal spaces that were historically hard to monetize. By investing in a purpose-built event sauna and programming Aufguss ceremonies, operators can charge separately for the experience on top of their general admission fee. This turns what was once a free-access amenity into a distinct revenue stream, while also making the thermal area more social and more attractive to guests who might not otherwise spend extended time in a sauna.

The same applies to every room in the facility: as you design from scratch, think about flexibility across the next five to ten years. What types of finishes support multiple uses? How does the space interact with adjacent areas? Can programming change the energy and purpose of a room at different times of day? A meditation class in the morning, a social gathering in the afternoon, and an Aufguss performance in the evening can all happen in the same room if the design allows for it.

Light tasks, not people, and treat the acoustics

In spaces where guests are in bathing suits, often nearly naked, subconscious comfort matters most. The recommended color temperature for bathhouse lighting is approximately 2,200 Kelvin, close to candlelight. At that warmth, skin tones soften, hard edges disappear, and people relax into the space rather than feeling exposed. The operating principle is to light tasks, not people. Nobody feels comfortable in a bath with a spotlight shining directly on them. Instead, light the pathways, the water surfaces, the architectural features, and let the guest areas stay in gentle ambient warmth.

This does not necessarily mean spending more on fixtures. It means spending more time planning where each light goes and what it illuminates. A lighting plan reviewed and revised before construction is far cheaper than retrofitting fixtures after opening.

Sound follows a similar logic. Bathhouse materials are predominantly hard surfaces: tile, stone, concrete, glass. Hard materials amplify and carry sound. Without acoustic treatment, a conversation at normal volume in one area can dominate the entire space. Acoustic panels, ceiling treatments, and strategic use of soft materials (textiles hung as art pieces, for instance, that never touch wet surfaces) can create zones where sound behaves differently.

The most sophisticated operators use finishes and lighting to create psychological zoning. Brighter light in the locker and check-in area cues social, active energy. Dimmer, warmer light in the thermal circuit cues quiet, contemplative space. Guests instinctively adjust their behavior, lowering their voices as the light drops, without needing to be told.

Storytelling and authenticity play a role here too. Through the late 1990s and 2000s, every other new spa was an “Asian spa” because that was the trend. Today’s guests, particularly younger ones who grew up with communal fitness and co-working and who treat social bathing as a normal part of urban life, actively root out inauthenticity. They vet the backstory. They check whether the cultural references are real or decorative. That shift from private luxury to communal experience drives demand for the social wellness category, and it rewards concepts built on real backstories over borrowed aesthetics.

But authenticity does not mean rigid adherence to foreign traditions. A sauna in North America does not have to operate like a sauna in Helsinki. The people who come to it live different lives. Some operators are building something new for their own market, even if it breaks the existing rules.

No published pro forma yet

Nobody in this industry has published standardized cost benchmarks, reliable per-feature operating costs, or a replicable pro forma, because the industry is too young and the variables between locations are too wide. For now, every operator is building their own model from scratch, and the mechanical and operational fundamentals are the constants.

Build your engine room first. Then build everything else around what it can actually support.

Update, September 29, 2026: This story now includes opening-investment ranges from the early results of a bathhouse benchmark survey.