What a home sauna kit assumes you have

RenoHouse (Toronto), a renovation firm that publishes a 2026 basement sauna cost guide, lists a prefab Finnish kit under the heading "Sauna shell / cabin" at $5,000 to $12,000 for the 4 ft by 5 ft to 5 ft by 7 ft sizes and $8,000 to $18,000 for the 6 ft by 8 ft to 8 ft by 8 ft sizes. Installation labour and electrical work sit in separate tables on the same page, and the room-side jobs follow in a list of their own. This site's indoor sauna cost guide carries both kit rows as kit only.

That split is the subject of this article. A kit is a room that gets built inside another room, and the other room is the assumption. The basement guide's table does not say what a kit contains, but RenoHouse's comparison of DIY and professional installs does: its worked example for a 5 ft by 7 ft Finnish kit build lists the kit as cedar tongue and groove, framing pieces, benches, a door and the heater, at $7,000 to $12,000. The sauna kit cost guide prices heaters on their own as well, so what a particular box holds is a question for the supplier.

Every room-side job below has a price on the same RenoHouse page or on its companion comparison of DIY and professional installs, which is what makes the gap measurable rather than a vague warning. These are the jobs that come back to the buyer on the day the kit is delivered.

A sauna panel is a finished interior surface. The wall behind it still has to keep heat in and keep moisture out of the building's structure. RenoHouse (Toronto) prices foil-faced insulation, R-13 in the walls and R-19 in the ceiling, at $400 to $1,200, and a sauna-grade aluminum foil vapour barrier at $200 to $500. This site's indoor cost guide carries the two together as one row of $600 to $1,700.

Those are small numbers against a kit price and large ones against the cost of getting the layer wrong. In its comparison of DIY and professional installs, RenoHouse ranks the wrong vapour barrier as the most common DIY failure: 6-mil polyethylene used in place of sauna-grade aluminum foil, which it says off-gasses and fails. Second on its list is cedar mounted directly to the foil with no air gap, which it says traps moisture, with mould developing in 2 to 5 years.

An uninsulated basement wall behind a kit also keeps drawing heat out of the room for as long as the sauna is in use, a cost that turns up on the electricity bill rather than in the build quote.

RenoHouse (Toronto) describes the ventilation for a basement Finnish sauna as a high-low layout: an intake low on the heater wall, 6 to 12 inches above the floor, and an exhaust high on the opposite wall, ducted to the exterior and never into the basement. It prices the inline exhaust fan, ducted outside and on a timer, at $500 to $1,500, and lists HRV or ERV integration as an option at $1,500 to $3,500.

The source does not say what moves a job within that range. What its description makes plain is that the duct has to reach outside, and a below-grade room may have no existing path to outside air anywhere near where the sauna is going. The panels arrive as a set; the route through the building does not.

The site's sauna ventilation calculator works out the airflow a given room needs from two published rules and shows where the inlet and outlet go, which is the conversation to have before the fan is priced.

RenoHouse (Toronto), in its comparison of DIY and professional installs, lists a floor drain for a basement sauna, marked "if applicable", at $1,200 to $3,500. Its basement guide treats the drain as optional too, naming an optional floor drain saw-cut in the demolition stage, and it prices the floor itself in the same room-side list as the fan: crystalline waterproofing on the slab at $300 to $900 and a porcelain tile floor at $800 to $2,500.

Not every home sauna gets a drain, and neither page says one is required. What the figures do show is that the floor is building work with prices of its own, separate from the kit, and that the decision belongs before the kit is standing on it rather than after.

RenoHouse (Toronto) prices a 10 mm tempered glass sauna door at $600 to $1,800 as its own line in the basement guide's room-side list, while the kit in its DIY example already includes a door. Which of the two a particular kit follows is worth settling before two quotes are compared, so the door is counted once.

Glass also changes the heater. Harvia's heater manual, which this site's sauna versus steam room calculator works from, treats every square metre of glass as 1.2 cubic metres of extra room volume when a heater is sized. The calculator's worked example puts 20 square feet of glass in a 6 by 5 by 7 foot room at about 79 extra cubic feet, enough to move that room from a 4.5 kW heater to a 7.5 kW one. Heater prices by output are on the sauna kit cost guide.

So the door belongs in the same conversation as the heater, not in a list of finishes chosen later.

On RenoHouse's page, electrical work sits in its own table, headed as ESA-permitted work by a Licensed Electrical Contractor. It prices a hardwired 240V circuit at $800 to $1,800 for a heater up to 6 kW and $1,500 to $2,800 for an 8 to 9 kW heater, and a panel upgrade on an older Toronto home with a full 100A panel at $1,800 to $4,500 or more. The electrical cost guide sets out what moves those numbers.

Assembly is the other assumption. RenoHouse prices prefab Finnish kit assembly at $1,500 to $3,500, the amount a buyer saves by assembling the kit themselves and pays if the plan changes once the panels arrive. For a full DIY Finnish build it estimates 80 to 150 hours of the owner's own labour over 3 to 6 weekends, plus the wait for permits and inspections. The installation labour guide sets that band beside the other kinds of sauna labour.

RenoHouse's own all-in table gives the comparison a kit price needs. A prefab Finnish kit with professional installation in a GTA basement runs $10,000 to $20,000 in total, and a semi-custom Finnish sauna with full basement integration runs $18,000 to $32,000. Set against the shell prices above, the all-in range is where the assumptions in this article have already been absorbed.

The DIY comparison makes the same point from the other side. For its 5 ft by 7 ft kit build with an 8 kW heater and a glass door, RenoHouse totals a full DIY build at $10,800 to $20,700 once electrical work, permit and ESA fees, materials, tools and a drain where needed are added to the kit, against $13,000 to $22,000 for the same build professionally installed, and puts the saving at $2,000 to $5,000 if everything goes smoothly. The two RenoHouse pages do not use identical ranges for a professionally installed kit, which is one more reason to read each figure as one firm's published estimate.

Some suppliers price whole saunas by seating capacity instead. SaunaFin (Concord, ON) says its lowest-priced saunas, seating one to two people, cost just over $2,000, and that saunas seating upwards of six to eight range from $8,000 to $12,000, with the cost varying by seating, building materials and the type of heating equipment. Whichever way a price is built, the jobs above sit in the house rather than in the box, and a quote that does not mention them has left them to the buyer.

Running cost arrives after everything else is paid. RenoHouse puts a 9 kW Finnish heater, used four times a week for an hour at Toronto's roughly $0.13/kWh, at about $5 a week or $260 a year, and says infrared runs roughly one-third of that. Those are the source's own assumptions, so the figure is a worked example rather than a rate, and the running cost calculator works the same sum on Ontario's published rate plans for any heater and schedule.

Of the 39 companies in this index, 38 carry the Saunas category. Reading their own websites, the index files 13 as installers and 12 as retailers, and leaves 14 unspecified. Google Maps labels 21 of the 39 as sauna stores, and the labels closest to the room-side jobs are thin: one general contractor, one bathroom remodeler, one carpenter and one electrician.

None of those records says who will insulate, duct, drain or wire the space around a particular kit, and the index holds no licence status or job history for any of them. Asking a kit seller which of those jobs it handles, and who does the rest, before the kit is ordered is the test the data cannot run. Thirty of the 39 have a website, the request form on each profile reaches SaunaIndex, which passes it on to one company listed in your area, and the saunas page lists them all. The indoor versus outdoor comparison covers the siting decision that comes before any of this.