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Community and Q&A

Sauna roof and wall assemblies

travismarttinen | Posted in GBA Pro Help on

I am planning to build a small sauna structure in Ontario with a zero overhang unvented roof, open-joint cladding with rain screen, Delta Fassade S membrane or similar on the walls (and possibly roof), DensGlass sheathing, rock wool insulation (R14), and a foil vapour barrier on the inside with taped seams.

The reason I want to use the foil VB on the inside is because people will be throwing lots of steam as well as washing up inside the sauna. The roof will be galvalume with 3/4″ strapping air space. So, will this system work? Or should I opt to use airtight DensGlass on the inside with a flash coat of spray foam under the roof sheathing as well as rock wool?

I have been having a hard time coming up with a solution because there is not much documentation of these types of assemblies being used on a sauna. Also, is there anything else inherently wrong with this assembly?

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  1. GBA Editor
    Martin Holladay | | #1

    I never imagined that I would be giving advice on sauna construction to a Finn! You're worried about the löyly, eh?

    Your proposed assembly sounds fine. Saunas stay dry -- because they are used intermittently, not constantly, and because they are so hot. Once everyone leaves the sauna, and the splashing stops, the heating unit or wood stove dries everything quickly.

    I wouldn't want to use DensGlas on the inside of a sauna. I'm a traditionalist -- use pine boards or cedar boards.

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