What Bathhouse Development Actually Requires

Everybody wants to open a bathhouse. The Instagram accounts are gorgeous, the revenue numbers from Bathhouse NYC are staggering (the company expects a $120 million run rate by end of 2026), and the consumer demand is real. Capital is flowing in: Bathhouse just raised $35 million for an eight-city expansion, and Sauna House is franchising the Nordic bathhouse format with data-backed unit economics. So the calls keep coming: entrepreneurs, hotel developers, fitness operators, nightclub owners, all asking the same question. How do I build one of these?

The honest answer is harder than most of them expect. A social wellness club is not a spa with bigger tubs. It is a complex hospitality operation built around heat, water, and humidity, three forces that will punish every shortcut in your 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.

The Real Cost of Wet

The single biggest mistake first-time operators make is underestimating cost. When experienced designers and architects in this space are asked what operators always get wrong, the answer is unanimous and immediate: cost.

Generic commercial construction costs in the United States run roughly $100 to $175 per square foot for a basic shell, and $200 to $450 for luxury finishes. Those numbers are nearly useless for a social wellness club. The moment you add heat, water, and humidity to a building, you enter a different cost universe. Specialized commercial construction for hydrothermal facilities, particularly those with hammams, steam rooms, and multiple pools, runs $250 to $600 per square foot for the thermal construction alone, before interior finishes.

Why so much more? Because everything that makes a bathhouse work 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, critically, any electrical rooms or parking garages beneath your slab). Drainage capacity that can handle 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, the most comprehensive reference document in 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. America has one of the strictest commercial building codes on the planet, and residential products cannot be used in a public facility. The sticker shock when operators learn the difference between consumer-grade and commercial-grade equipment is, by all accounts, universal.

Your Building Starts in the Mechanical Room

The most counterintuitive rule in bathhouse design: 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 actually be. Get this wrong and nothing else matters.

How wrong can it go? 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 constantly. 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.

The lesson is straightforward: bring your thermal and MEP (mechanical, electrical, plumbing) specialists in at the same time as your spa consultant and your architect. Not after the concept is done. Not after the investor presentation. 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.

What does the engine room actually need to accommodate? At minimum: 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.

The Third of Your Space Nobody Wants to Build

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. It is labyrinth-level planning, and it takes time. 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:

• Pool draining: New York City code requires pools to be emptied every two weeks. Most other cities do not. This has significant operational and water-cost implications.
• Changeroom requirements: New York City’s Department of Health does not recognize a universal or genderless changeroom. You must provide designated female and male changing areas, which effectively doubles your changeroom, shower, and bathroom square footage. In Canada, universal changerooms with private change stalls are standard and code-compliant.
• 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, not because they want to spend more, but 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 specifically, there is a persistent misconception worth clearing up. There is no public pool in the United States that can legally operate without chlorine. 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 chlorine, which is odorless. 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 not a nicety but 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

One of the clearest design principles to emerge from experienced operators and designers is: never build a single-purpose room if you can help it. 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.

The most dramatic example of multi-use thinking is a hammam designed for a hotel spa in Miami that turned out to be the largest in North America: roughly 24 feet in diameter and 20 feet tall. The spa director, thinking creatively, 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.

This principle connects directly to the Aufguss movement, which is giving 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 broader lesson 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.

The Invisible Design: Lighting, Sound, Atmosphere

The most experienced designers in this space will tell you that the things guests feel but cannot name are often more important than the features they can see. Lighting is the clearest example.

In spaces where guests are in bathing suits, often nearly naked, subconscious comfort is everything. 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 signals social, active energy. Dimmer, warmer light in the thermal circuit signals quiet, contemplative space. Guests instinctively adjust their behavior, lowering their voices as the light drops, without needing to be told. This is design doing the work of operations.

Storytelling and authenticity play a role here too. Something fundamental has shifted in how guests relate to wellness spaces. 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. This generational shift, from private luxury to communal experience, is the demand signal that makes the entire social wellness category possible, and it rewards concepts built on genuine narratives 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 are on a different life journey. The most exciting operators in this space are creating something new for their own market, and if that breaks all the existing rules and has never been done before, so much the better.

Bottom Line

A social wellness club is a hospitality business that happens to feature heat and water. The guest experience is what brings people in and keeps them coming back. But that experience is entirely dependent on the mechanical, structural, and operational systems behind it. The mechanical room determines the guest room. The linen flow determines the guest satisfaction. The code compliance determines whether you open at all.

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. That data will come. For now, every operator is building their own model from scratch, which makes the mechanical and operational fundamentals in this article that much more important: they are the constants in a business where almost everything else is still being figured out.

The operators who succeed will be the ones who treat the unglamorous work, the engine room, the linen storage, the drainage capacity, the code research, with the same seriousness they bring to the design, the programming, and the brand. The ones who skip that work will spend years and significant capital learning the same lessons the hard way.

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