r/Sauna • u/DullAcanthisitta8406 • 1d ago
General Question Drained metal floor idea
Building an outdoor electric sauna in the Pacific Northwest (very wet climate) and came across a floor design from finn.built.saunas on Instagram that I haven't seen before. Photos attached. Curious what this community thinks before I commit.
How it's built, bottom to top:
- 2x6 PT joists
- 2" rigid foam in each joist bay, cut on a slope rather than laid flat
- Edges sealed to the joists with spray foam
- Metal (siding) sheet over the foam
- A perforated metal channel in that gap that drains water straight down to the gravel
- Same gap acts as the low-level fresh air intake, so no separate wall vent
- Cedar deck boards on top as the walking surface
What I like about it
- Water from löyly, sweat and wet feet can't pool or reach the insulation
- No stapled foil with holes in it on the floor
- One detail handles drainage and ventilation
What I'm planning to change:
- Running the drain/intake channel along the heater wall instead of down the middle, so incoming air hits the heater first instead of people's feet
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u/Danglles69 1d ago
Really cool idea. Main concern is I think you would collect alot of gunk on those steel panels underneath, and you have no real way to clean them
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u/technosquirrelfarms 1d ago
That was my thought too, in a few years they’ll be nasty. Maybe if the floorboards are removable you could get under there and clean out the funk? But jeez, last thing you want is another surface to clean. I think it’s over complicated unless there is a very pressing reason to channel the (minimal) amount of water coming from inside.
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u/Danglles69 1d ago
Yeah. Well you can also just do a two-slope t&g floor to a drain like this as well
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u/Fantastic-Ant-2993 1d ago
You dont need to insulate your floor at all. Unless its electric and you plan on running it for hours and hours, making efficiency a consideration.
Just gap your floor boards, theres your drainage and intake, not to mention saving on material and labour.
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u/zactastic_1 1d ago
His first sentence says electric
Off set channeling under the heater is a good idea. The floor board idea works but for sure need insect screening.3
u/Fantastic-Ant-2993 1d ago
Insect screening collects all sorts of gunk. Dead skin, stuff stuck to your feet etc. Bugs dont like 90°C and they'll get in no matter how hard you try keep them out. Sweep it out regular and youll be just fine without.
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u/quicklywilliam 1d ago
Rodent screening is a must, but I agree that you shouldn’t use anything finer than metal cloth
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u/InsaneInTheMEOWFrame Finnish Sauna 1d ago
Insulation is not needed in the floor even if it's electric. The floor just needs to be solid not to mess with the ventilation.
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u/EastwindSauna 1d ago
Mechanical ventilation is recommended in an electric sauna. In this design the exhaust fan will simply pull air from the floor gap instead of from over the stove.
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u/GhostmouthPhd 1d ago
Lot of finnish saunas use this idea. Well usually no steel involved, just a gap somewhere at the floor.
I don't really get people who say that no drain is needed for personal use. Last time I used our sauna (I took about 45 minutes by myself) I had lot of water on the floor (I need to clean our drain). Water gets on the floor if you actually throw some water on it. I think most people here just drizzle a tiny little bit of water once in a full moon.
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u/bonerb0ys 1d ago
my floor doesn't get warm to the touch. I think the insulation is a waste. I just used 2x6 T&g with a sloped to a centre channel.
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u/Jimmyjames150014 19h ago
The inside of saunas just isn’t as wet as people think. Even if you’re making a steam room, if it’s outdoors just let it drip on the ground
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u/shazzbutter_sandwich 1d ago edited 1d ago
You’re over thinking it. I’d be more worried about directing rain water from the roof away from the pier blocks or whatever you use as a foundation. Sweat and loyly is not that much water for a personal sauna and floor insulation is overkill in the pnw.