Russian Banya / Finnish Sauna
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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.
Foundation
There are two basic types of above-ground structural foundations:
- pier involves vertical posts upon which the foundation rests.
- skid involves laying a foundation directly on the ground
- in either case, make sure string outline is square by measuring diagonally from corners
I ended up using a pier foundation, with treated 4x4 posts inserted into Camo deck blocks, with each block sitting on a 4” hole filled with gravel.
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:
- 8’x10’ fits 7-10 people
- 5’x7’ and 6’x7’ popular for home, fits 3-5 people
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.
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.
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
- frame with 60”x84” space between wall studs
Wall framing
- 2”x4”s for headers and plates
- 2”x4”s for framing studs
- make sure your spacing of studs works for whatever sheathing material you are using
- place load-bearing wall studs 16” apart and non-load-bearing studs 24” apart
- start by marking the bottom and top plates every 16” (except first and last marks, which are 15.25” from nearest mark)
- note that the so-called 2”x4” is actually 1 1/2” by 3 1/2”
- add horizontal supports between studs at height where benches can be screwed in
- secure all frame joints with two 3 1/2” nails
Roof framing
- run roof rafters longer than needed
- cut “birds mouth” slots into rafters where they sit on top of wall top plates
- can bolt rafters to walls with hurricane ties
- stove pipe thimble can insulate and space the stovepipe where it goes through the 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
- standard = 24” x 72”
- rough opening = 26” x 75” (1/2” more on each side than actual door size for wiggle room)
- headings are 1” wider than door on both sides, plus another 3” extra total
- handle made of wood
- non-metallic door catch available from sauna dealers
- leave air space below door of 5/8” to 1” for oxygen
Vents
- intake vent below heater near floor
- exhaust vent towards the ceiling on other side of room
- perhaps a second exhaust under the benches
- 3”x10” duct space
Insulation
- high-temp aluminum foil vapor barrier with shiny side in (Type C single-side foil)
- start from bottom of wall and work up so higher sheets overlap lower ones
- use aluminum duct tape to cover seams and tears`
- conventional fiberglass insulation batts (usually come in 15” widths for standard stud openings)
- R13 for walls
- R22 or R26 for ceiling
- can put two layers of R13 laid in perpendicular orientation`
- consider recycled cotton insulation rather than fiberglass, because it’s easy to work with and non-toxic (brand name UltraTouch by Bonded Logic)
- floor doesn’t need insulation
- caulk bottom of walls meeting floor
Interior
Wood and nails
- deciduous trees
- western red cedar, aspen, spruce, hemlock, pine?
- some varieties may leak melting sap which can hurt
- tongue and groove boards of 1”x4” or 1”x5” nominal widths
- with the grooves facing down so water can’t collect into them
- galvanized 1.5” nails
- 5D galvanized small head siding nails
Heater
- drum stoves are popular because doesn’t require welding.
- preferable to feed wood from predbannik, although more complicated to run stove through wall
- volcanic rocks placed on top of heater to retain heat
- wire mesh to hold rocks in place
Benches
- use thick 2”x2” or 2”x3” or 2”x4” planks
- avoid knots in wood since these heat up more
- fastened w/ screws on underside
- two-tiers
- L-shape?
- long enough to stretch out
- generally allow two feet of bench for each person on the upper bench
- 1/2” gap between planks
- lower bench should be 18” from floor and 17” deep for strength
- upper bench should be 18” higher than lower bench, about 3 1/2
- 4 ft from ceiling and 20” to 35” wide for comfort
Lighting
Most pundits agree that lighting should be discrete and dim.
- ~60W light bulb, weatherproof and heat proof encasement if placed high up.
- Finnish tradition would be a candle window between the predbannik and the banya
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.
References
- http://homesaunakits-since1974.com/Sauna-Building-Aids/106-sauna-building-how-to-build-a-sauna.html#1-buy-a-sauna-kit-to-do-it-yourself
- framing tips: https://www.mycarpentry.com/framing-carpentry.html
- https://web.archive.org/web/20060126211339/http://cankar.org:80/sauna/building/design.html
- tour of 8x8 sauna: https://www.youtube.com/watch?v=56nP5u3FAbI&t=333s
- tudor shed plans: https://www.buildeazy.com/plan_links_sheds.html
- pretty shed: http://www.livingroofsinc.com/wp-content/gallery/s-h-e-l-t-e-r/p4190156-copy.jpg
- stove clearances: https://cdn.shopify.com/s/files/1/1661/5331/files/nippaInstallManual.pdf?3150570655419202463
- cross-section of shed design: http://shedplanspackage.com/wp-content/uploads/2013/11/work-shed-designs-2.jpg
- nice overview of building features: http://bouldersauna.com/
- kit company with useful layouts: http://www.finlandiasauna.com/pdf/Finlandia_Sauna_Brochure-WEB.pdf
