Thursday, May 5, 2011

Finnish Sauna: Design and Construction

Finnish Sauna: Design and Construction (6th revised edition, 2007), published by Rakennustieto and compiled with the assistance of 15 Finnish authors, is probably the best book about sauna construction I have read.  Unintentionally I also checked out the 2nd edition from 1995, which is oddly longer (mostly due to the later removal of several illustrations, reorganization of sections, removal of in-text advertisements, and omission of the cleaning chapter).  As all construction books should be, this one is heavily illustrated.  One spends as much time pouring over the drawings as reading the text.  The final section of the book is a photo montage of “Contemporary Finnish Saunas” that are peerless in their beauty, but largely beyond my ability or means.  I will include below passages from the text I found helpful.  As time allows I might work these into a proper blog entry, or not: 

In a good sauna, heat is conveyed symmetrically, which means that the bather feels heeat evenly from all directions and there is a balance between convecteed and radiated heat (26). 
The traditional manner is to place the window at a low elevation, whereby most of the light falls on the floor in front of the stove (42). 
In placing the light fittings and directing the light, the upper part of the sauna and the seat level of the platforms should remain in darkness, but the steps and route of access should be lit... Normal lighting is required for cleaning the sauna (87). 
Darkness is usually felt to be a pleasant aspect of the mood of the sauna (97). 
If the stove is next to the door, it should be hinged on the stove side (43). 
[The cooling area] if possible should face the setting sun and a scenic view (44).  (Yes!  Mine will.)
[Vapor insulation] overlaps must be at least 15cm wide, affixed with heat-resistant tape, and pressed against each other betwween two wood surfaces (48). 
(Pages 49 through 52 contain wall, floor and roof sections for saunas of different types.  Using their labeling scheme, I have a US2 wall, AP2 floor, and YP1 roof)
[Year round sauna] windows are usually triple glazed, three paned insulating glass with a ventilation shutter that can be opened (54). 
Spruce [Picea abies] with few knots is well suited for all surfaces in a sauna... To minimize cracks caused by drying, the boards must be sufficiently thick in relation to their width... Countersunk nails are recommended for the lining... Horizontal cladding (as opposed to vertical) is a better solution, since there will be a gap admitting air between the upright bottom battens [the boards to which the cladding is nailed] and the parts behind the lining boards [the cladding] will be ventilated... The wooden wall lining is not extended down to the floor (56).  [Red or yellow cedar is never mentioned!  The cover image appears to exemplify these recommendations.]
A waterproof surfacing material [for floors] is a plastic mat with welded seams (57).  [what does “welded seams” mean?]
(Pages 62 through 63 have diagrams of removable bench construction.)
A sturdy railing is built around the stove to prevent the bathers from falling onto it and also to serve as a footrest.  It should include a lower rail element for children.  The railing can be made of wood or steel and faced with wood (65).  [Can this be made removable for access to the stove?]
Rubber stops are nailed or screwed to the lower surface [of wooden duckboards] to facilitate drying (66). 
One of the most common problems is the presence of ferric sulphides (pyrites) which release sulphuric oxide and sulphuric acid into the ambient atmosphere when the stones become worn (78). 
The intake air of the stove room is located... to prevent draughts or cold downward draughts onto the floor (84).  [Preheating the air in the dressing room is best.]
Palsi's law: the bather must be seated with his or her whole body (including the feet) above the stove stones [in smoke saunas] (95). 

The description by Nestor of Kiev in his chronicle from 1112 supports my earlier argument that saunas are cathartic.  From page 5:  Nestor tells of hot wooden saunas, in which naked bathers beat themselves with branches and finally pour cold water over themselves.  “Without any coercion they torture themselves and in this way gain pain instead of cleanliness”, tells the chronicle.