Building a sauna
Wood, stones, insulation and kits for building your own traditional sauna, with nothing in the hot room that off-gasses.
How we rank building a sauna
- Materials 45%
- Durability 20%
- Safety 10%
- Trust 10%
- Value 15%
Why, and what each one means
We rank materials first (45%): a hot, closed room concentrates whatever the wood, glue and barrier give off, and almost none of it is tested. A 2022 lab study found that heat treatment cut terpene emissions but raised formaldehyde, furfural and acetic acid (PubMed (opens in a new tab)), so thermo-aspen scores no higher than natural alder. Cedar can trigger asthma in some workers (PubMed (opens in a new tab)), so we flag it. Barriers and insulation are scored on stated ingredients and fire ratings.
- Materials 45%
- Untreated solid wood, sauna stones, foil and mineral wool: nothing glued, stained, sealed or plastic on the hot side, and the species and grade named.
- Durability 20%
- Holds up to years of heat and steam: clear grades without knots for benches, stones that do not crack.
- Safety 10%
- Fire and heat ratings for insulation and barriers, and clear guidance on clearances.
- Trust 10%
- Highest when the maker names everything, answers questions, and has no recalls, warning letters, Prop 65 notices or lawsuits over safety or labeling. Points come off for unresolved problems and for paid promoters it does not disclose.
- Value 15%
- Price per square foot or per kilogram against the others here that pass.
Each product scores every one from 1 to 5, and its rating is the weighted average. We list only products rated 3 or above that break none of our rules.
We avoid
- Plywood, MDF, glued finger-jointed boards, stains or sealers in the hot room.
- Foam insulation or plastic vapor barriers on the hot side.
- Pine and other resinous woods for benches, which weep sap when hot.
Read the research
Know one that fits? Suggest a product
7 products · best rated first
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ROCKWOOLROCKWOOL Comfortbatt Stone Wool Insulation, R-15, 3.5 in
Non-combustible stone wool batts, GREENGUARD Gold certified per ROCKWOOL, with flame-spread and smoke ratings of 0. ROCKWOOL labels them “Red List Approved”, not formaldehyde-free; its AFB evo is the formaldehyde-free version. -
ThermoryThermory Alder Sauna Wall Boards, profile STS4 (natural alder)
Natural alder wall boards from Thermory, an Estonian maker that publishes declarations of performance, a verified EPD and forest certificates. Nothing is added, but no one tests what the hot boards give off, and prices vary by store. -
HarviaHarvia AC3000 Sauna Heater Stones, olivine diabase, 5 to 10 cm, 20 kg box
Angular dark-gray olivine diabase stones, matching the olivine-dolerite Harvia’s manual lists as suitable. Nothing is added, but Harvia publishes no analysis and says stones crumble and need rearranging yearly. -
ProSaunasProSaunas Sauna Foil Radiant and Vapor Barrier, 48 in x 80 ft roll
Solid aluminum foil barrier on kraft paper, with no plastic film or bubble core, sold as ProSaunas. The stores give heat and vapor ratings but no test report or fire rating, their coverage figures disagree, and prices differ by store. -
Finnish Sauna BuildersFinnish Sauna Builders Custom Indoor Sauna Room Pre-Cut Kit, 4 x 6 x 8 ft
A pre-cut indoor sauna room kit of named woods, clear bench stock and a foil barrier, for a 4 x 6 ft room. You supply the frame, insulation and wiring; the barrier, bucket liner and light are not described, and no warranty is stated. -
ProSaunasProSaunas Western Red Cedar Vertical Grain Sauna Boards, 1 x 4 (S4SEE, sold as clear grade A+)
Untreated, vertical grain Western red cedar bench boards from ProSaunas. The maker names species and treatment and gives a two-year warranty, but no grading rule or certificate. Cedar can trigger asthma, and it is the priciest wood we list. -
ThermoryThermory Thermo-Aspen Sauna Bench Boards, profile SHP (thermally modified aspen)
Heat-treated aspen bench boards from Thermory, smooth on four sides, with no chemicals added in the process. A 2022 lab study found heat treatment raises formaldehyde and furfural emissions, so we rate it below natural wood.