Buying an indoor sauna comes down to four questions: which room, how much electrical capacity you have, how moisture will leave that room, and whether you want a kit or a built room. Get those settled and the rest — wood species, heater brand, bench layout — is preference. Get them wrong and you will either be rewiring a house or discovering mould inside a wall in year three.
Indoor saunas are the more practical choice for most households. They cost less all-in than outdoor builds, they need no foundation or weatherproofing, and — because they sit steps from a shower — they get used far more often, which is where the actual benefit lives. This guide covers the full sequence.
Step 1: Choose the room
Ranked by how well they usually work.
Basement
Why it works: the most available space in most houses, a concrete floor that tolerates water, often near a drain, ceiling height usually adequate after dropping to 7 feet, and construction noise disturbs nobody.
Watch for: ceiling height before dropping — you need about 7'6" of existing height to finish at 7 feet with a dropped ceiling; existing moisture problems, which a sauna will make worse; egress and head height under ducts; and whether the panel is on the same level, which usually it is.
Full detail in how to build a sauna in a basement.
Bathroom or ensuite
Why it works: already waterproofed and drained, adjacent to a shower — which is the single best predictor of frequent use — and the room is already designed for humidity.
Watch for: space, which is usually the binding constraint; the need for a separate ventilation path; and whether removing a bath or a closet is acceptable.
Garage
Why it works: space, tolerance for construction, often existing 240V service for a dryer or workshop, and no loss of living space. Under-rated in most homes.
Watch for: insulating the sauna envelope properly against an unconditioned space; dust; vehicle exhaust if the garage is in use; and the walk from the garage to a shower.
See how to build a sauna in a garage.
Spare room, closet or bonus room
Why it works: viable for small cabins, especially infrared units that plug into a standard outlet and need no construction at all.
Watch for: floor loading on upper storeys; carpet, which should come out under a traditional sauna; ventilation, which a bedroom rarely has; and the distance to the nearest shower.
See how to convert a room into a sauna.
Distance to a shower or cold source. A sauna twenty steps from a shower gets used four times a week. One on a different floor gets used four times a month. This outweighs every other consideration about the room, including size.
Step 2: Check the electrical capacity
Do this before you shortlist anything. It is free and it decides the budget.
Traditional saunas need a dedicated 240V circuit sized to the heater:
| Heater | Approximate breaker |
|---|---|
| 4.5 kW | 20–30 A |
| 6 kW | 30–40 A |
| 8 kW | 40–50 A |
| 9 kW | 50 A |
| 10.5–12 kW | 60 A |
What to check at the panel: free breaker slots, main breaker rating, and how far the panel is from the intended room.
A full 100A panel in an older house. Adding a 50A sauna circuit then requires a subpanel ($1,000–$2,500) or a service upgrade ($2,500–$6,000) — costs that have nothing to do with saunas and can exceed the price of the cabin. Find out now.
Infrared cabins are much easier. One- and two-person units commonly run on a standard 120V outlet; four-person units usually need a dedicated 20A circuit or 240V.
The wire run matters too. At 6 AWG and up, copper is expensive and the route through finished walls is labour. A sauna directly above the panel is a different job from one at the opposite end of the house.
Full detail in sauna electrical requirements.
Step 3: Plan how moisture leaves the room
This is the step that separates a sauna that lasts twenty years from one that causes a building problem.
The vapour barrier
On every wall and the ceiling. Not polyethylene — foil, which reflects radiant heat as well as blocking vapour. Its job is to stop hot, moist air migrating into the wall cavity, where it condenses inside the insulation and framing. This is the single most important detail in an indoor sauna build, and it is invisible once the cladding goes on.
Ventilation
A sauna needs air exchange while running and needs to dry afterwards.
- Inlet low, near or under the heater, so incoming air is heated immediately
- Outlet on the opposite wall, low to mid-height, with an adjustable closure
- Often a third high vent used only for drying after a session
Where the outlet goes matters in an indoor build. Exhausting into an adjacent hallway or a finished basement moves hot, moist air into the house. Ideally it ducts to an exterior wall or into a space that is itself ventilated. Plan this at design time.
Full detail in sauna ventilation.
Drying out
After bathing, open the vents and leave the door ajar so the room dries. A sauna closed up wet after every session will develop odour and staining. This is a habit, not a feature, but it is worth designing for — a door that can be propped, and a vent that is easy to open fully.
Floor and drainage
A floor drain is a genuine luxury and not usually necessary in a home sauna. What matters more is a floor that tolerates water: tile, sealed concrete or a proper sauna vinyl, sloped gently to a drain if you have one. Never carpet. Never unsealed wood over a wood subfloor.
Note that tile is a heat sink — it adds roughly 1.5 kW per square metre to the heater requirement. See what size sauna heater you need.
Step 4: Kit or custom-built?
Pre-cut kit
Panels, benches, door, trim and often the heater, supplied to a standard size. Assembles in a weekend for a competent DIYer.
Strengths: predictable cost; everything is designed to work together; the vapour barrier and insulation are typically integral to the panels; fast; no design decisions required.
Weaknesses: fixed sizes, so you fit the room to the kit rather than the other way round; limited layout options; usually one or two wood choices.
Typical: $3,000–$13,000 depending on size and wood, plus heater and electrical.
Custom-built room
Framed, insulated, vapour-barriered and clad in place.
Strengths: exact fit into an awkward space; any dimension; sloped ceilings, odd corners and existing obstructions can be worked around; any material; any bench configuration.
Weaknesses: costs more; takes longer; and depends entirely on the builder understanding sauna construction. A general contractor who has never built a sauna will often get the vapour barrier, the ventilation or the bench height wrong.
Typical: $8,000–$25,000+.
See custom sauna vs sauna kit and DIY vs professional installation.
Pre-fab infrared cabin
Clip-together, 1–3 hours, often plugs into a normal outlet, no construction. If you want infrared, this is essentially the only route and it is a good one. See traditional vs infrared.
Step 5: Size and layout
Size for normal use. A room for six used by one person costs six people's worth of energy every session.
| Capacity | Interior footprint |
|---|---|
| 1–2 seated | 4' × 4' |
| 2 seated + 1 lying | 4' × 6' |
| 3–4 people | 5' × 7' |
| 4–6 people | 6' × 8' |
Ceiling: 7 feet. Below 6'6" the upper bench is cramped; above 7'6" you are heating air nobody sits in.
Benches: allow 2 feet of length per seated adult, and at least 6 feet on the upper bench if anyone wants to lie down. Upper bench about 42–48 inches off the floor, lower bench about 18–20 inches below it, and your head should sit at or below the top of the stone basket.
Door: outward-opening, never latching, tempered glass, wooden handle. Outward-opening is a safety requirement.
See how much space you need for a sauna.
Step 6: Materials
Interior: non-resinous softwood only.
- Western red cedar — aromatic, stable, stays cool, the premium default
- Nordic spruce — the traditional Finnish choice, pale and clean, excellent value
- Hemlock — light and nearly odourless; the right pick if cedar's scent is too strong
- Thermally modified aspen or alder — the best bench surface, because it never gets too hot to sit on
Hardwood, knotty pine for benches, plywood, MDF, or anything treated, painted, stained or sealed.
Benches deserve their own decision because they are what your skin touches. Thermally modified aspen or clear cedar are the two safe answers. See best wood for saunas.
Lighting: must be rated for sauna temperature and humidity, and positioned so it never glares at someone lying on the upper bench. Under-bench or behind-backrest LED strips rated for the environment are the usual answer.
Step 7: Heater
Size it by volume — cubic feet ÷ 45–50 — then add for glass, tile and any uninsulated exterior wall. Then check the circuit that heater needs against your panel.
For an indoor sauna specifically:
- Wall-mounted heaters suit tight rooms and keep the floor clear
- Under-bench heaters are excellent where the heater should be invisible, at the cost of stone capacity
- Floor-standing models give much more stone mass and better löyly if you have the floor space
- Remote or Wi-Fi control is worth more in an indoor sauna than anywhere else, because indoor saunas are the ones used on weeknights
Full detail in how to choose a sauna heater.
What to check before you commit
- Panel capacity, free slots, and distance from the panel to the room
- Ceiling height available, before dropping to 7 feet
- Where the exhaust vent will discharge
- Whether the floor tolerates water and how the room will dry
- Distance from the sauna door to the nearest shower
- Whether the largest kit panel fits through your narrowest doorway or stairway
- Heater kW including glass and tile adders
- Whether the kit includes a vapour barrier and insulation, or assumes you provide them
- Whether the heater is included, and whether a control panel and guard rail are
- Permit requirements for the electrical work
Getting the sauna into the house
An overlooked logistics problem that occasionally stops a project outright.
From the kerb to the sauna location: doorways, hallway width, stairway turns, ceiling height on the stairs, and any fixed obstruction. Then ask the manufacturer for the largest single panel's dimensions and weight.
A 5' × 7' kit typically has panels around 7 feet long. A basement stair with a 90-degree turn and a 32-inch doorway at the bottom may not accept them. This is discovered on delivery day far more often than it should be.
Weight. A cedar kit for a four-person room can weigh 600–900 lb in total, in panels of 40–120 lb each. Carrying those down a flight of stairs needs two fit people and a plan.
Ask about delivery terms. Kerbside, threshold, or inside delivery? Liftgate included? Is there a residential delivery surcharge? These are separate line items on freight and they add up.
If the route genuinely will not work: a pre-cut lumber package — cladding cut to length rather than pre-assembled panels — solves it, because individual boards go anywhere. So does a custom build. This is one of the more common practical reasons people end up building custom.
Noise, smell and living with an indoor sauna
Small things that affect daily life and never appear in a specification.
Heater noise. Elements tick as they heat and cool, and metal expands audibly. Water on stones is loud. If the sauna shares a wall with a bedroom or a home office, insulate that wall for sound as well as heat while it is open.
Cedar smell. Strong for the first few months, then settling to a pleasant background. Most people love it. A minority find it overpowering, which is the main reason hemlock exists as an option.
First-firing smell. Every new heater should be run for an hour or two with nobody inside, well ventilated, to burn off manufacturing residues. Expect a distinct smell and plan to do it with windows open.
Humidity in the surrounding room. A sauna releases moisture during löyly and when the door opens. Good sauna ventilation handles it; a dehumidifier in the surrounding space is a cheap insurance policy in a tight basement.
Heat in the surrounding room. The area immediately outside the sauna will be warm. In summer, in a conditioned house, that is a cost. In winter it is free heat.
Electricity spikes. An 8 kW heater is one of the largest loads in a house. If you are on a time-of-use tariff, scheduling the preheat off-peak is worth real money and costs nothing to set up. See how much it costs to run a sauna.
Frequently Asked Questions
Where is the best place to put a sauna in a house?
A basement is usually the best combination of available space, tolerant flooring and construction access, followed by a large bathroom, a garage and then a spare room. The single strongest predictor of how often the sauna gets used is distance to a shower, so a slightly smaller sauna next to a bathroom will beat a larger one two floors away.
Do indoor saunas need ventilation?
Yes. A traditional sauna needs an air inlet low near the heater and an adjustable outlet on the opposite wall, plus a way to dry the room after use. Indoor builds need particular attention to where the exhaust discharges — venting into a hallway or finished basement moves hot, moist air into the house. Ideally it ducts to an exterior wall.
Can you put a sauna in a bathroom?
Yes, and it is one of the better locations — the room is already waterproofed and drained, and being next to a shower means the sauna gets used. Space is usually the constraint, and the sauna still needs its own ventilation path rather than sharing a bathroom extractor sized for a shower.
Does an indoor sauna cause moisture problems?
Not if built correctly. A taped foil vapour barrier on the warm side of the insulation on every wall and the ceiling, working ventilation, and the habit of drying the room after use prevent it. Moisture problems in indoor saunas are almost always traceable to a missing, punctured or untaped vapour barrier — which is invisible once the cladding is on.
How much does an indoor sauna cost to install?
A pre-cut traditional kit typically runs $3,000–$13,000 for the cabin, $1,000–$2,200 for a heater and stones, and $500–$1,500 for a dedicated 240V circuit where the panel has capacity — roughly $5,000–$16,000 all-in for a self-assembled build. A custom-built room starts around $8,000 for the room alone. Infrared cabins start well below all of that and often need no electrical work.
Room chosen and panel checked?
Related guides
- Indoor vs Outdoor Sauna
- How to Choose the Right Sauna for Your Home
- Sauna Ventilation: Complete Guide
- Sauna Electrical Requirements
- How to Build a Sauna in a Basement
Published by Finest Saunas