Surf Deep
9/5/2005
I am considering a metal roof for my woodburning sauna. The condensation issues here have me seriously thinking otherwise. My sauna plan is a 7' t&g cedar ceiling over a vinyl vapor barrier with fiberglasss bats outside/above the vapor barrier. There would be a ventilated 3'attic above the ceiling. Should the metal ceiling be installed on plywood/felt above the trusses, or would a purloin system above/on the trusses be preferred? The Sauna is 8'x7' and is attached to a 10'x 10' storage shed. All sauna walls and ceiling will have vinyl vapor barrier. The sauna floor is an uninsulated concrete slab. Are my construction ideas sound? The climate is Milwaukee area. Advice and direction is asked. I'm doing this myself...no contractor. Thanks! Deep
Todd Miller
Isaiah Industries, Inc.
9/5/2005
Most residential metal roofs are designed to be installed on decking with underlayment on top of that. Your construction method sounds good except I would use the decking and underlayment. Make sure the roof has adequate pitch for the product you choose. Make sure that you have good ventilation, both intake and exhaust. There are non-ferrous metals you can use if you wish -- aluminum, copper, zinc.
Guest User
9/6/2005
Thanks Todd for the reply. By decking and underlayment, are you referring to plywood with roofing paper? What thicknees/grade plywood? Is ferrous metal an issue here? This is new construction. Any other helpful hints for sauna roofs/construction? Thanks! Surf
Todd Miller
Isaiah Industries, Inc.
9/6/2005
I really do not have any information specific to sauna construction. Yes, by decking I was referring to CDX plywood or OSB. CDX might be better for this as it is less prone to moisture absorption I believe. Most metal roofing products have been tested on 1/2" decking. Underlayment could be 30-pound felt or one of the newer synthetics -- see what the roofing manufacturer suggests. You seemed concerned about possible corrosion / rust of the metal due to the high humidity conditions. I think that you're taking steps to avoid that being a problem. However, I threw out non-ferrous metals as a possible option to avoid that concern.
Greetings Deep from an old Milwaukeean. I too have a sauna, however it has no vapor barrier or insulation or ceiling for that matter. I live in Maine and the snow builds up on the roof (3 or 4/12 pitch) and sometimes melts when we sauna, but there has been no leakage and no undue wear on the roll roofing over the years. I would like to throw a couple of ideas at you for your consideration. First you say you have a vapor barrier and then insulation. There is new thought on attics that have that type of construction and that is to NOT vent the attic. Moisture comes into the attic thru the vents and then condenses on the timber. Then in winter it freezes on the cold rafters. Sealing the attic prevents this from happening, and there have been studies that the heat buildup is not enough to shorten the life of the asphalt shingles (a moot point if you are using metal roofing which vents itself under the ribs). All that is required is adequate insulation (I have R-54 on the ceiling in my house) to keep from losing heat to the attic, but that is more for the conservation of energy than any other reason. (I built the house with vents and then plugged them to see if it worked, and they are still plugged.) As for your sauna though, it would be the perfect place and save you money to just apply the roofing to the purlines and have the whole sauna attic empty and totally vented. Then you wouldn't have to worry about protecting the insulation by sealing, venting, etc. Barns have metal rooves applied that way, even those with cattle and all the moisture coming from them. Not having to buy the insulation for the ceiling would also save you money and because your sauna is small, it would not be hard to heat. (Mine is 8x8 and 14' high at one end and 8' on the other. The walls are constructed with 3/4" siding, 2.5" studs with FG in the cavities, 6-mil poly, and 3/4" cedar on the inside, and takes about a half hour to bring up to temp on a moderately cold winter nite, and I have a relatively small stove made from a piece of 12" water pipe.) Here is a pic of the sauna (with white door) and a temporary shed attached while we built the house. The front space of the sauna is all glassed in - greenhouse in summer, and wood storage, and entrance lock/dressing room in winter.
Sorry, didn't realize that pic would need a magnifying glass to see the sauna in the back. Don't have one of it by itself.
Todd Miller
Isaiah Industries, Inc.
9/7/2005
Thanks Richard for weighing in on this!
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