Banya design

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Foundation

There are two types of above-ground structural foundations: pier or skid

  • 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

Pier foundation

  • lay out outline of walls w/ string
  • mark out every 4 feet along string
  • dig 12" below frost line (check village inspector about depth of frost line)
  • bury treated 6x6 posts or sona tubes (tubes filled w/ concrete)
  • attach/set anchor bolt in center of each post
  • attach 6x6 post to anchor

Skid foundation

Size

  • no taller than 7', otherwise lower areas do not retain heat as it rises
  • 8'x10' fits 7-10 people
  • 5'x7' and 6'x7' popular for home, fits 3-5 people
  • inside dimensions should be multiples of 12" for standard tongue and groove interior boards

Floor

  • doesn't need insulation
  • plywood subfloor paint or waterproof sealant
  • durarock covered in a coat of vinyl cement repair, or simple cement tile, cement, tile, or something that won't absorb water on top
  • duckboard floors are often placed on top - removable sections of 1"x3" or 1"x4" wooden slats with 1/2" spacing between the slats
  • cut shower drain in center, ideally sloping floor towards drain
  • can use vinyl cement patch 40# and trowel it onto subfloor 3/4" around perimter, sloped to 1/4" at drain

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

  • use only single glazed tempered glass, not double-glazed because they fog up

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

  • lighting should be discrete and not cast shadows
  • 60W light bulb, weatherproof and heat proof encasement
  • or follow Finnish tradition with a candle window between the predbannik and the banya

Plans

Banya plans. Note that no windows or doors are indicated yet.

top down
front
side

References