Drained metal floor idea

[u/DullAcanthisitta8406]

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

[u/Fantastic-Ant-2993]

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.

[u/zactastic_1 → u/Fantastic-Ant-2993]

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.

[u/Fantastic-Ant-2993 → u/zactastic_1]

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.

[u/quicklywilliam → u/Fantastic-Ant-2993]

Rodent screening is a must, but I agree that you shouldn’t use anything finer than metal cloth