knowledge-kitchen / domestic-construction

Russian Banya / Finnish Sauna

.

Research into the construction of a Russian banya (or Finnish sauna) - a necessity for any home. Construction began 2 December 2024 and was completed about 2 months later.

Model

Banya/sauna plans. top front side

Dimensions

Most American sources advise to build a sauna/banya no taller than 7’, otherwise, they say, lower areas will not retain heat as it rises. Apparently, this is utterly wrong. Finns and other sauna enthusaists say to build no less than 8 1/2’ tall for proper hot air circulation and comfort when raising arms.

My sauna/banya’s hot room dimensions are approximately 8 1/2’ tall with 5 1/2’ x 7 1/2’ floor space. The changing room (or predbannik) floor space is 3 1/2’ x 7 1/2’.

Occupancy

Some recommendations I’ve found for occupancy, which seem correct to me:

Foundation

There are two basic types of above-ground structural foundations:

I ended up using a pier foundation, with treated 4x4 posts inserted into Camo deck blocks (strong plastic alternatives to concrete blocks), with each block sitting on a 4” hole filled with gravel. In retrospect, I should have created a large perfectly flat gravel bed under the entire structure plus a bit extra. But I was doing this in winter when the ground was frozen and very difficult to dig up. A large flat gravel bed would have been simpler.

Floor

2x6 treated lumber for floor joists. I used 3/4’ oriented strand board (OSB) for subfloor, although plywood would generally be recommended for more moister resistance. On top of the OSB, I’ve added a layer of tar paper. On top of the tar paper, I sloped the floor towards a central drain cutout using the Ben Square Method. Above the sloped strips is cement board, with large slate tiles on top.

Floor insulation

There are various views on whether floor insulation is necessary. I did not use any in order not to make it any easier for opportunistic mice to find a cozy home. I have not noticed any problems with heating the room, although the floor is certainly cold to start.

Duckboard

While I have not done so, some banya/sauna builders place “duckboard” panels on the floor for added comfort. These are removable sections of 1”x3” or 1”x4” wooden slats with 1/2” spacing between the slats. Water drains between the gaps and does not pool up on the boards.

Framing

Standard stick framing

Walls

Studs and plates:

Ensure your spacing of studs works for whatever sheathing material you are using

Roof

Windows

Insulated tempered glass is preferable, although many use whatever regular glass is available. Any window will reduce the heat retention. As long as the stove is strong enough, this is not a problem.

I have a fixed insulated tempered window in the hot room, a small regular piece of glass removed from an old door used as a window separating the hot room from the predbannik, and a cheap vinyl big box store tilting basement window with a bug screen high up in the predbannik wall to the outside.

Door

Opens outwards

Vents

Insulation

Some notes I’ve collected about insulating and waterproofing of a stick frame construction banya/sauna:

Line the interior with high-temp aluminum foil vapor barrier with shiny side in (Type C single-side foil)

Suggested insulation values between studs/joists:

I ended up using Rockwool “Safe ‘n’ Sound” for the walls and “ComfortBatt” R23 for the ceiling. Rockwool is called a “mineral wool” or “stone wool” material, made of spun molten mineral, stone, or ceramic material. The interior is lined with foil vapor barrier and seams are taped with aluminum tape.

Interior paneling

Wood

Deciduous trees

After struggling with the decision, I used very generic cheap readily-available pine boards for the walls and ceiling paneling, using the best quality pieces for the benches, walls, and ceiling where people will sit, and knottier and lesser quality pieces in other less important areas. I am very happy with the result. In retrospect, the pining by many (pun intended) for cedar and other photogenic woods seems like a distraction for a sauna/banya enthusiast who just wants a good schvitz.

Heater

I bought a Harvia Pro 20 sauna stove, which can heat a larger space than I need. I also bought the matching Harvia pipe/chimney since this was my first time assembling a stove and I was concerned about ill-fitting parts. Stoves are expensive, but may be the most important investment. In retrospect, all my earlier concern over the correct insulation and paneling wood has melted away… just get a nice big strong stove, make sure you provide good ventilation, and you will be happy.

Remember that you are trying to avoid a sauna experience that resembles what you find in a typical gym or hotel in North America. You need a lot of heat, good air circulation, and proper placement of benches. That’s it.

Benches

I built L-shaped benches from the same pine wood I used for paneling, but into 2 inch strips spaced about 1/2 inch apart. Despite the wood being slightly thinner than recommended, I provide sufficient support bars under the strips so that there is no sagging. The paneling wood works very well, although the foot bench becomes dirty and stained easily. I may apply a “mineral oil” treatment to the foot bench to try to make it more impervious to dirt/staining. My bench tops are removable for periodic cleaning/sanding, but the bench frames are fixed.

Lighting

Most pundits agree that lighting should be discrete and dim.

In the predbannik, I retrofitted a Danish-style PH5 lamp with a solar-powered LED bulb. In the hot room, I placed the solar-powered LED bulb hanging under the bottom bench for ambient light. A glass window showing the fire in the wood burning stove mixed with dim solar-powered lighting creates a great ambience in the hot room and does not require electrical connections to the outside, except simple plastic conduits hidden under the paneling that connect the small solar panels attached to the outside to the bulbs inside.

References