A great idea for your sauna floor

A word on building your own sauna and dealing with the sauna floor.

Here’s an email exchange that may offer some guidance:

Hi Glenn
The Saunatimes.com website has me a converted man…I no longer want an outdoor sauna, now I NEED one!
I live in Surrey, BC. Our winters are mild by Minnesota standards but the dampness and rain chill a person to the bone.
I have started to aquire the materials to build my outdoor sauna and have a few questions about the ideal outdoor sauna design.

1. The opposing bench design looks like a good idea on paper but I noticed your portable sauna has L-shape benches. Is there a change of “ideal”?
2. Flooring in the sauna and change area. Any recommendation on how to finish them or does bare plywood stand up alright?


And my response:


Wonderful email, and i’m glad to have helped and influenced you.  You ask two great questions:
1. “L” bench is the more ideal… yes, change in “ideal sauna” glad you caught it.
2. Plywood floor.  Yes, start with plywood as a subfloor, then:

  1. Paint it or treat plywood with a water sealant.
  2. In the hot room, I suggest screwing in a drip edge around your perimeter.  Your first row of t&g cedar can rest on that.  I rip a 2×3 green to get a 45 degree upper edge.
  3. cut and install a shower drain in center of hot room.
  4. get a couple bags of vinyl cement patch, 40# i believe. it’s cheap.
  5. mix that in a wheelbarrow.
  6. trowel it down in the hot room floor.
  7. 3/4″ around perimeter, down to about 1/4″ at the drain.

It’s a real slick system…. couple points to keep in mind..

  1. keep your bottom plate in tact where your door is, or sawzall it and screw it down so your cement has a place to stop.
  2. consider patio block where your woodburning stove will sit.  Lay that first, before cement.  trowel up to patio block.
  3. chalk line your drip edge before screwing it down to bottom plate, framing, as a trowel mark, guide.
  4. You don’t need much of a pitch if you’re sauna building is level.
  5. You’ll build cedar decking (1×4 cedar with 1/2″ spacing) on top of this.  this is where you’ll walk.  feet stay dry.

take pictures!  keep in touch.

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26 thoughts on “A great idea for your sauna floor”

  1. I just have a quick question, is there a reason you suggest vinyl cement patch instead of regular cement?


  2. Hi Saara, were are building the same sauna and have the same questions. The vinyl cement patch is roughly $30 at Lowes, did you ever get an answer to your last two questions. thanks

  3. I just finished building our German outdoor sauna in Ontario! We are sooooo happy and learned a lot in the process.
    We learned that insulation is everything, especially when you want also large windows. we even made our own door.
    So, we insulated our floor with 6″ rocksol. On top of that is 3/4 espenite, followed by 1/2 cement board, followed by a natural cut stone floor tile from Home Depot; followed by a douple layer of hard wax sealer. The cement board is fibreglass reinforced, and a must for a tiled floor.
    We did not put a floor drain in. For the few drops of sweat you may loose on the floor, you simply use a damp cloth to clean with, whenever you think it’s time. In a German sauna, we do not touch the wood with our bodys; instead we we sit on towls and make sure the sweat is caught by towls at all the times. This is nice and soft for the body and your wood will last a long time, looking like new. However, sauna wood should be treated with odorless paraffin (food grade).

  4. Hello Michael,

    I wonder if you could send me some pics of your sauna. Are you from Germany? My family moved from Germany to Canada in 2002. I’d like to start building an outdoor Sauna next year and would appreciate some pictures if possible.

    Thank you,
    Gerhard Becker

  5. Gerhard: I am from Minnesota, USA land of 10,000 lakes and fewer saunas, but we are gaining on them. As far as photos of my saunas, please search “12 16” on saunatimes. You’ll see my cabin sauna. Search “backyard sauna” and you’ll see folks detailing their saunas, as well as stumbling across photos of my backyard sauna. Hope this helps.

  6. Yes, I am from Germany (where men and women sauna and lounge together nude, without having shame or sexual thoughts). I came to Ontario/ Canada winter ’89, and settled in the Muskoka region.
    When said I just finished our outdoor sauna, I said a little too much. I still work on small things like foot benches, preserving the wood, etc.
    I started this project in July, with the goal to create an oasis, that is pleasing to mind, body and soul; they way it’s done in Germany. But since money is always an issue with such lofty goals, I did did and made everything myself including lamps, sauna bucket, ladle, etc. I documented every step and have a lot of pictures. I am not sure, how I would post pictures here. I can however email some, if I get an email address to send them to.
    Anyone, who wants to visit and check out our sauna is welcome.

  7. Hi Glenn,

    I have been building a sauna using your DIY ebook and it’s been a great help, thank you! I was wondering if you had any pictures of the duckboard you describe making in the book that you can share?



  8. Does anyone else use paraffin oil to treat their benches? I’m at a crossroads and looking for any helpful input.
    I’ve read from many people who are adamant that the wood should be left untreated, and have also read many articles talking about using 100% paraffin oil to preserve the wood.
    I’m sure there are some strong opinions here too! Anyone have a list of pros/cons?

  9. Hey Glenn,
    I’m thinking of building a sauna that is connected to a bath house. It’s a 16×8 ft structure that has a 6×8 sauna and the rest is going to be a bath house that includes plummed in shower, washer and dryer and sink. Do you think I should just build two structures to keep the sauna from being a fire hazard or potentially warping the rest of the bath house due to heat and moisture? I just purchased a Kuuma wood stove for it btw. Any thoughts would be greatly appreciated. Cheers!
    Tyler (Alaska)

  10. Hi Tyler:

    I’d build one structure. It’s more efficient this way. a 6×8 hot room is ideal so hats off to you for that. Concerns of too much moisture can be minimized by good venting. As far as fire hazard goes, the Kuuma is “safety first.” It’s a very safe stove. Just keep the ash pan closed (except for first couple minutes of lighting, but Daryl Lamppa frowns on even this).

    Sounds like a great project, and you’ll be resonatingly warm this winter!

  11. We just finished out first night in our new outdoor sauna. We need to put a finish on the outside of our sauna made of hemlock. Suggestions on a finish? We are thinking a clear finish to keep the natural look. Also, how often does someone clean(or in this time disinfect) their sauna. Does the sauna need to be disinfected between other users during this covid time? Thanks for any suggetions!
    Paul and Kelly sauna podcast listeners!

  12. Hi Paul:

    Outside finish:
    Good thinking on clear, to show off the beauty of the wood grain, but i’ve seen bad effects of clear exterior stain. Bubbling, mold underneath in dark areas, and now you’ve got to periodically maintenance. The elders at our island cabins are all big on opaque penetrating stain. Many in our lands go nuts for 2 part Sikkens. My thinking is talk to 2-3 painter pros, that know your wood and your climate and go with the consensus.

    Clean/disinfect hot room:
    now that one I have a clear answer for you:

  13. Hey Glenn, I am finishing up the floor on my first sauna and looking at the floor from the doorway entrance it looks like there might be a problem with water getting under the sleepers at the doorway since there is no way to seal it with the vinyl cement. What would you recommend to seal this area off?? Thanks in advance! Soren

  14. Hi Soren:

    It may be too late for you and your build, but when I build (and I think I have this in my ebook) but when constructing the common wall, it’s a good idea to keep the bottom plate and work around that for the hot room drip edge, sleepers, durarock, etc.

    For your situation right now, i’d lay down a cedar 2×4 to define the two rooms – hot room and cool room. Then a little more vinyl cement to seal it off. A wet sponge to clean off your cedar threshold.

  15. Hi Glenn,

    We’re building a smaller sauna on a cement slab. We’re also going to finish the entire cement slab with 1.5 inch flagstone on mortar. I’m thinking it makes the most sense to do all the flagstone first, then put duckboard over the floor of the sauna. As far as pros and cons, having the sauna walls on the flagstone might make them a little uneven and allow air to come through the floor plate cracks. However, I feel like building the flagstone up around the outside of the sauna (which it would do since it would be almost 2 inches higher), would mean water would drop into the sauna base. Thoughts?

  16. Sean:

    I’d defer to a tile guy for their advice, and my hunch is that would suggest what I am thinking: i’d go with 2x green bottom plate on the slab, secured by hurricane ties, as this is how it’s done for garages, additions, etc. but that’s just me (beating to a conventional drum).

  17. Hi Glenn,

    So I am hoping to build a sauna on a trailer! I have been trying to figure out how to do the floor, and your advice above seems perfect! I was a little unsure about what the drip edge you described looks like. Would you mind elaborating a bit on that?

    And how do you level the boards on top of the sloped floor?


  18. Matt:

    For mobile, instead of cement board (Durarock) and skim coat, we are finding much better results by gluing one cut to size sheet of nickel pattern vinyl flooring to our trailer’s 3/4″ marine plywood base. Then, where the flooring meets the wall, we install a drip edge. The drip edge, either 2×3 or even 1×4 is green treated stained and painted. We run a bead of calk or silicone down, as we screw the drip edge securely to the wall. Then a bead where the floor meets the drip edge.

    For drains, we put in two. One in each corner under the bench.

    Now, here’s where it took us a college education to figure out drain (ie. a couple of beers). Being mobile, the chance of having the sauna level from side to side is pretty much zero. So, we just pitch the trailer ever so slightly to be tongue high or low, so that if we spilled our 5 gallon water bucket, voila. It all goes down the drain.

  19. Hi Glenn,
    Bought your e-book 2 years ago and have been chipping away at it ever since. Just picked up my Finnleo Himalaya 9.0 stove today. Electric, I know, but still super stoked! I have a question about using clear cedar as a drip edge instead of pressure-treated lumber. I think I bought a a few clear cedar 2x4x8s too many. Can I use them as a drip edge instead of the 2×3 greens? I have a couple of 2x6x8 greens, but they’re that red kind with the holes from where the chemicals get injected. I think it won’t look as nice with the clear cedar t&g butted up against it. I’m looking for other drip-edge suggestions. Do I even need a drip edge? Going to do your durarock/ skim coat floor with a drain, not sloped (I’m getting impatient). Your site is so amazing! I look forward to sharing photos of my project when it’s done. THanks!

  20. Matt: Such a great question!

    Ok, the key here is “wicking.” I suggest a 2×3 green because if we stain it or paint it, or even leave it, it’s a break between your floor and your cedar wall.

    Imagine if someone – not you of course – but someone else spilled a water bucket and it ran along the floor. This is what we want to be thinking about, about creating a break. If you use this clear cedar, it’ll look beautiful, but if water gets against it, it’ll get wet and janky, stain and be yucky. It’s a buzz kill, I know, because i’m right there with you about wanting to use this extra material, but let’s think about making shelves instead.

    Bottom line: bite the bullet. Go to Home Depot. Rip 2×6 green or get dry 1×4 material. prime it and paint it. Make this material water impervious (wow, didn’t need spell check for that), and secure that over your foil, where wall meets floor. You’ll be happy you did.

    A break between wall and floor is a very good thing.

    Yes, please share photos! I’m super happy you’re advancing, Matt. A perfect time to get yourself in gear for your first sauna round. Happy for you.

  21. Hey Glen,

    I’m building a small mobile build. I have your ebook and am looking into trying to figure out the best floor and drain for my mobile build. I just have a few kinks wrapping my head around it. I’m doing osb on top of the trailer pressure treated boards. Durarock would be sweet because I like the asthetic and utilization of it. but if there’s any way around not doing that what’s this about the vinly? also what drain do you recommend for sauna and what would be a piping set up for it to run out the bottom of trailer? any recommendations and suggestions would be so helpful. Like I said, I have your ebook and love it, i’m just doing a specific mobile build that I need to get sorted out! Thanks so much man!

  22. Hi Glenn,

    I’m converting an old gazebo into an outdoor electric heated sauna. What are your thoughts on using some Azek (plastic wood) as the floor/wall drip edge? Could there be benefits over the green wood you suggest? I have some scrap here already I could use but don’t want to if you say its a bad choice. I could easily prime and paint it prior to installing. Thanks!

    PS I have parts of your ebook memorized.

  23. Hi,
    I have a outside floor frame of treated lumber and subfloor sitting on 4 inches of washed 3/4 aggregate and want to use it for a sauna floor but need to know what should be done on top of that to complete this western red cedar outdoor sauna. Thank you

  24. Larry,

    You have a couple of options at this stage, and they are detailed in Sauna Build Start to Finnish. If the upsell doesn’t resonate, it’s ok, as the free relevant information for you is that if the subfloor is on top of the washed aggregate, i’d consider searching “Ben Square Method” on this website as an idea generator.

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