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Sauna Floors

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Looking to Pitch Your Sauna Floor and Install a Drain? Consider the Trevor Trowel Fill Method

People often ask during their sauna build: “do I really need a floor drain?” Well, the best answer is always “yes.”

Why is a sauna floor drain a good idea for a proper sauna?

A proper sauna is one in which if:

  • Someone wants to bathe in the sauna hot room, they can.
  • Kids want to have a friendly water fight in the hot room, they can.
  • The sauna owner wants to hose out or rinse out the hot room, they can.

How Do We Pitch a Sauna Hot Room Floor to the Drain?

Working up from the subfloor, we rip sleepers on our table saw, and glue and screw them down to our subfloor to create a pitch for the cement board. We create sleepers in a bicycle spoke arrangement like so:

We create a slight and gradual slope, so that when we glue and screw down durock, then skim coat it with vinyl cement, our floor is sealed and water will run to the drain.

A great way to ensure a solid floor is to run the sleepers in the bicycle spoke fashion, then, with a $10.00 bag of premium cement (no rocks) backfill the gaps between the sleepers with cement. Use the sleepers as a trowel guide to ensure a smooth finish. Run a wet sponge along the sleepers so that durock can lay flat.

The Trevor Trowel Method creates a really firm, well supported (and sloped!) base for our cement board.

Trevor also ran cement board up the wall, via his patented “sauce pan” method

I have built sauna floors every which way from Tuesday. I am a huge fan of vinyl cement repair. Check out this post on how to skim coat cement board for a “smooth clean finish.” As Trevor illustrates above, he has created a solid water tight floor that sheds water down to the drain. The floor is perfectly ready to accept a duck board overlay floor (gentle for bare feet and keeps feet dry) or even a “3rd step” for more vertically aligned hot rooms that get the sauna bather climbing up to an upper bench.

Slope Your Hot Room Floor with the “Ben Square” Sleeper Method, and Enjoy a Water Fight in Your Sauna Hot Room

Every once in a while, through sauna building user engagement, I am “wowed” with an enhancement to the sauna building methods detailed in my ebook.

User engagement with other sauna builders has allowed me to cross pollinate different ideas and methods. No ego, but with intent to help the next guy down the road. And just as with the Zen and Art of Motorcycle Maintenance, we have the author drawing parallels to understanding the mechanics of his motorcycle as empirical learning towards other aspects of life. I have enjoyed discussing different approaches to the nuances of sauna building with others as crazy as I am.

Because my eBook is in digital format (vs. printed), every once in a while we pick up on a better way to do an aspect of the sauna build. And thanks to the non patent process of copy & paste, I am able to share the enhancement with the next sauna builder coming down the pike.

With my ten or so sauna builds, I have always run 2x stock through my table saw to create sleepers on an angle through my table saw, sloping down to the drain, like so:

From Ben

“Like any other engineer, I can’t help tinkering with a good design. Here is a picture of my floor slope method. I will put reinforcements at the Durock edges as well. Pieces are ripped in 1/8″ increments. Reinforcements for the edges of the Durock will also be added.”


  1. By adjusting our table saw to rip 2x stock in decreasing widths, we create a uniform slope to the drain. IMG: Glue and screw sleepers at decreasing widths to drain
  2. Cut Durock and mark sleeper locations. IMG: Marking sleeper locations on Durock
  3. Transfer marks onto Durock. IMG: Transferring sleeper locations with a T square
  4. Now this is a kick ass sloped floor glued and screwed and ready for the vinyl cement skim coat stage. IMG: A perfectly sloped and supported sauna hot room floor

A well built sauna hot room should be such that if kids want to have a hot room water fight, an adult need not have to say “Don’t do that!”

Video: the Ben Square Method

Is There a Better Way to Seal Our Sauna Floor?

I’ve done it every which way ’til Tuesday. Rubber mats, Red Guard, etc. etc. But I like this method the best. The three “F’s” of skim coating:

  • Frugal: $50 all in. Durock is relatively inexpensive, easy to cut and lay down. $8.00 – $9.00 for a 3’x5′ sheet. A bag of vinyl cement is well under $20.00
  • Forgiving: Well mixed vinyl cement is easy to trowel and works its way into cracks and mistakes like nobody’s business
  • Fast: All this takes about 20 minutes (and is actually kind of fun!)

How to Prep Cement

How to Prep the Floor

How to Lay it Down

The “Finnished” Product

From the Mailbag: A Great Idea for Your Sauna Floor


SaunaTimes reader says: The SaunaTimes website has made 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 acquire 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 changing area. Any recommendations on how to finish them or does bare plywood stand up alright?

I say: Wonderful email, and I’m glad to have helped and influenced you. You ask two great questions:

  • “L” bench is the most ideal… yes, change to “ideal sauna” glad you caught it.
  • Plywood floor. Yes, start with plywood as a subfloor, then:

Paint it or treat plywood with a water sealant. 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. Cut and install a shower drain in the center of the hot room. Get a couple bags of vinyl cement patch, 40# I believe. It’s cheap. Mix that in a wheelbarrow. Trowel it down on the hot room floor. 3/4″ around the perimeter, down to about 1/4″ at the drain.

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

  1. Keep your bottom plate intact where your door is, or sawzall it and screw it down so your cement has a place to stop.
  2. Consider the patio block where your wood burning stove will sit. Lay that first, before cement. Trowel up to the patio block.
  3. Chalk line your drip edge before screwing it down to the bottom plate, framing, as a trowel mark, guide.
  4. You don’t need much of a pitch if your 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. Your feet stay dry.
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130 thoughts on “Sauna Floors”

  1. 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

  2. I purchased your guide about 1 year ago, thank you! I was going to use think set on concrete board to create a slight slope for my tile floor. My concern/thoughts with this method would be a leak into the wood fir strips between the wood deck and the cement floor. Reaction or ideas?

    Thanks you

  3. Skim coat your concrete board w/ vinyl cement repair. Then duck board over that. This method has worked well for me for 10 or so sauna builds. Outside of a full slab pour, If there’s a better method, I’d like to know about it.

  4. FYI, I ended up adding additional strips in 1/16″ increments to keep the spacing under 3″. The floor ended up extremely stable. Thanks for writing this up Glenn!

  5. David. Good one. I can tell that you are thinking. That solution is one of the key tricks, and I have it detailed in my ebook. Basically, you rip a 2×6 green and run a 45 angle on it and screw it into bottom plate tight against sub floor. First course of T&G cedar rests on the drip edge, and durarock butts up against the drip edge. Then blue tape the drip edge and vinyl cement right up to the edge.

    You can pour water down the wall and it won’t get up in behind there.

  6. How do you prevent water from seeping into the subfloor at the edges where the dura rock meets the vertical wood wall?

  7. 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).

  8. 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

  9. 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.

  10. 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.

  11. Hello Glenn, why not use cedar boards for the drip edge instead of the green weathershield boards? Thank you. Asaph

  12. i like the question, Asaph. You can use cedar 2x stock for drip edge. For some weird reason, i’m partial to treated (about the only place i’m partial to treated) and i think it may have to do with that spot where the durarock meets the drip edge. This is a potential “wet for awhile” spot. Cedar can handle it, but treated seams like it can take it better/more, if there’s extensive moisture. Good one, though. Your question got me thinkin!

  13. Glen
    This is my first sauna build after moving to the Rockies. I’m unclear whether the drip edge goes on top of the cement board or do the sleepers and the cement board butt up against the drip edge? Do you use silicon caulk around the drip edge? It seems like your Ebook says the drip edge goes on after the foil wrap and after sloping the floor with the sleepers and covering it with the cement board. Is this correct? Ben’s photos look like the cement board and the foil wrap meet. Are they covering the drip board or is it yet to be applied. Thanks in advance. Jim

  14. Jim: there are a couple ways to do this. My extended experience (yes, as detailed in my ebook) is this:
    1. Foil wrap your hot room, tape all seams and ends.
    2. Glue and crew in drip edge to bottom plate along hot room floor perimeter. This will lock and seal the foil, sandwiched against the wall bottom plates.
    3. Glue and screw down your sleepers. Run a course of sleepers tight against drip edge along perimeter of hot room floor (to prep for our durarock sloped floor).
    4. Glue and screw durarock to floor. Butt the durarock against drip edge along floor. Use factory edge of durarock as much as possible against the drip edge. Try to orientate your cut sides for butting against durarock, or shave the cut sides real smooth to help with a tight fit, that seam butted against your drip edge around the perimeter.
    5. Skim coat your floor, being sure to get some of that vinyl cement along the drip edge, sealing off that area.

    You can run a bead of silicon calk around the drip edge if you like. And this is good left brain thinking as this material has expansion capabilities, even more than vinyl cement.

    As we scratch our heads and think about this system, in the context of a water fight in your hot room:
    1. Water running down the walls, will meet the drip edge and run onto your floor, and find its way down the drain.
    2. Water poured on the floor, like a 5 gallon bucket spilled by a clumsy sauna guest, will rush against where the wall meets the floor and go nowhere but will turn around and find its way down the drain via your sloped floor.

    I advanced this system above as I started building my mobile saunas. Theory being that a sauna bouncing down the road, the hot room walls may want to move around a bit, opening up these corners. The drip edge creates a transition from wall to floor, ensuring those seams are sealed well, and permanently.

    And to get more geeky, anytime we have a transition from one medium to another, in this case stone (durarock) to wood (cedar), we have a seam that is vulnerable to opening up. Different mediums expand and contract differently. So, A job is the right job here.

  15. 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?



  16. 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?

  17. Love the idea!
    I’m curious if you use water in your sauna or is it electric? Wondering how this would hold up to water being on it.

  18. I use a lot of water in both my sauna hot rooms that each have this floor solution. I’m a big fan of how it seals off and makes waterproof.

  19. This is an interesting system. We have pretty low, damp ground at our camp (near the shore of Lake Michigan in MI’s UP) and would like to build a sauna. I think a slab might crack unless we messed around with a lot of fill… I’ve also thought about putting it on posts to keep it stable in the freeze/thaw over the year. Would either of those be necessary, though? Would a mobile sauna with this type of sleeper system floor be stable enough to be set down in this kind of location?
    I LOVE this site, by the way!

  20. Hi Mary: Glad you are enjoying Saunatimes! There three options to support your sauna structure:, 1) slab on grade, 2) pillars, 3) float. These are in order of most elaborate to easiest. And you point out the pros/cons, below, For many sauna structures, #3 is the ideal choice. Especially if the structure is not too big. An 8×12 can float very effectively, even in the worst soil conditions. Wet clay areas can freeze unevenly and move a structure like a boat on Lake Superior in November. But with a small structure, it ain’t no big thing, as we can easily shim and level block as things may move, and often the points of contact move at the same amounts.

    Anyhow, a mobile sauna liberates oneself from all these shenanigans. We roll up and level, and in the case of using an ice fish house chassis, we can re-level as needed. And get this: instead of a sloped floor to drain, we can control the slope the entire structure. So, we can put in a couple drains, in each corner, and pitch our mobile sauna ever so slightly to one corner. Nobody will know the difference, but the water on thes floor will.

  21. Hello Glenn,
    The skim job looks great! Easy too. I have 2 questions post reading your ebook a few times now.
    1. My build is coming along and I was just introduced to Extreme Green sheeting. It’s a magnesium oxide board that works like dura rock but is smooth , I bought all the needed 4×8 sheets, did the trever square tapered sleeper s and am perplexed on how to seal it. Sorta new product with not much inside tips yet. Question is do you think The vinyl crete coat seal job above mentioned will work on the Mag/oxide board.
    2. Bigger question is My Kuuma stove is on the way, it has an 8″ throat which will be fed from changing room, I already built pedestal in hot room for stove being in the corner (with heat shields) and it will be 11″ off the wood framed wall, with 2 layers of the extreme green board (1″ air gap between) for a final distance off finished wall of 7-9″ per Kuumas’ details. Problem is the through wall for throat which is now wood, soon to be metal studs with Extreme green (fire proof) on both sides and throat hole of 18.25″ wide. Im told we need 16″ non combustible around throat but all other dimensions including pad were built around the closer numbers. Is there a creative solution to not have to eat up more hot room floor by moving the stove away from side wall. As it is I can easily get 11″ inch offset from wood wall but the 16″ is gonna make for a bunch of tear out and redo and worse than all it will eat up hot room bench space. Sorry for the mouthful, hoping you have a creative solution. Thanks!

  22. Timothy:

    1. i’m not familiar with extreme green. I’d say test out a remnant piece with the skim coat. i’m an old dog with the durarock, and just love how it sucks up the vinyl cement, so hopefully you’ll have same results with your product.

    2. I hear you on the rip up, but I want to say, it’s ok to go one step forward and one back and then another forward in another direction. it happens all the time with everything and may as well happen with our sauna builds. You are needing to have clearances to non combustibles big time if you’re going to go with the outside feed/throat extension. It’s critical you do it right. And you’re going to feel tons better when you get your stove rocking and you can whisper ‘lampomassa’ three times as you toss water on the rocks.

  23. Greetings, Glenn. I hope you and yours are enjoying a wonderful sauna season. I have a question about the floor method you describe above, using the combination of concrete board and the vinyl cement patch product. Just to be sure–Does this create a final surface that is waterproof? Lastly, does water “bead up” on this floor surface and if does not, then is the water soaking into the flooring below? Or should it be treated with a concrete sealer product?
    Many thanks for all you do for the world’s sauna traditions!

  24. Hi Dustin:

    When mixed and applied properly, the vinyl cement is waterproof. The trick is to trowel it along the face of durarock that is sloped to the drain.

    You’re welcome! Keeping the tradition alive.

  25. 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)

  26. 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!

  27. 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!

  28. 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:

  29. Could you use ‘Z flashing for the transition from foil to durarock? Same idea as the 45 degree board yes?

  30. Yes, Mary. For sure. I like the 2x stock for drip edge concept as it gives us some dimension, some thickness for the durarock floor as transition.

  31. Glenn,
    Do you have a picture of of drip edge method? I’m still not quite sure how it’s done. They say a picture is worth a thousand words. 🙂 Thank you Glenn.

  32. Great questions Kevin:
    1. filling the sleeper void: You can do this. Otherwise, the durarock is strong enough to span about 4″ or so between sleepers. Lately, we have been filling the void. A 80# bag of mortar mix goes a long way. If filling the void, it’s important to dry fit the durarock first, and then when laying it down for good, after filling the void and troweling, be careful when screwing it down. Maybe stand on a 3/4″ remanent piece of plywood so your weight is carried across many sleepers.

    Oh, an advantage of the bicycle spoke method is that you can use some blue tape on the drip edge tto mark where your sleepers run.

    2. glue and screw. If filling the void, chances are the tops of the sleepers will be yucky and cementy from over pour and troweling, which is actually better than under pouring and under troweling. In this case, forget the glue and just screw down the durarock.

    Glad you’re rockin’ Kevin!

  33. Hello Glenn, I see that you fill the void between sleepers with cement while using the spoke method. Am I correct in thinking that you do not need to do the same when using the square sleeper method? If so, I assume that the cement board is strong enough to span the spaces between sleepers? Also, I see reference to glue and screw. I know that the sleepers are glued and screwed to the subfloor, but are you using adhesive between the duroc and sleepers also? Thanks for all the great info!

  34. 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

  35. 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.

  36. Hi Glenn:

    Totally reasonable to run your cement board up the wall a bit. One thought is to skim coat your cement board before screwing to your wall, keeping gravity on your side.

    You can always use more vinyl cement or sealant as a second coat or patch job after it’s applied to the walls. I’ve done this several times and it works great. Even a car wash sponge to rub on the cement, then trowel after for that smooth clean finish.

  37. Glenn,

    I am considering going up the sides of my hot room 6-12 inches of cement board and sloping the floor from that and bypassing the drip edge. I would then skim coat after that. Is this reasonable?

  38. Hi there, am considering a sauna build, I have a 6×7 shed built on a concrete slab that I hope to use. This shed is rotting out and I will have to replace some siding and the treated wood sill plates at the bottom. This is in large part due to the slab—water runs under the shed, the wood soaks it up etc. From what I can tell unless I jack the shed up on bricks or something there is no way around the issue.

    My question is—is a drain and sealed floor necessary if water is going to come and go under the sill plates regardless? I’ve thought about grading the floor towards a corner and drilling a hole through to the gravel pad. My worry is if I seal the floor water will get trapped under the sill plate anyway. I’ve read that caulking/sealing along the sill plate is worth a try but I figure water will still end up getting through. Would love to hear your thoughts!

  39. Here’s a crazy thought. Maybe jack up the building and replace the sill plate/bottom plate with a double green 2x with gaps along the perimeter. Fill the gaps with good wire to keep rodents out, and you’ve created a breathable hot room. “That which blocks our path creates a new path?”

    This may not be your answer, Andy, but it may help bring you to the answer.

  40. That is a great idea and similar to one of the solutions I was thinking of. Perhaps I am confused—is a ‘green’ a #2 PRIME PRESSURE TREATED WEATHERSHIELD per the item list? Thank you for feedback!

  41. Garth: Yes, exactly. Seal everything on the floor up to the drip edge. This has worked great for me. The floor of my cabin sauna has held up for 24 years now and counting (and with heavy use) as well as my backyard sauna, 17 yrs now and also counting, with also heavy use.

  42. I have been working on my sauna for the last two years. It’s in the corner of our 32′ x 40′ steel shed just outside Pella, WI. Used white cedar from blow-downs harvested in our cedar swamp. 880 board feet sawn for just $80 locally; then milled/ T&G for $237. What a bargain! I’ve used Glenn’s E-book all through the process. I used stringers on my sauna floor in a pattern starting with 3/4″ against the wall down to 1/16″ at the drain. Nailed and glued. Then dura rock with vinyl cement patch. After that dried, I bought a Rust-Oleum epoxy product at Menards ( a little pricey, but not too bad) with copper-metallic color and anti-slip additives. It is spectacular! And…….even more waterproof than just vinyl cement patch. Not sure how or if I can post pictures with this comment. If someone knows how…..I’d appreciate the help.

  43. 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?

  44. 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).

  45. 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?


  46. 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.

  47. Hi Glenn,
    Just finished roofing the sauna “shed” building, and moving inside to the sauna part. Finally starting to get real!

    A question about how much Quikcrete Vinyl Cement I need. In these pandemic times of intense building supply demand, I can’t find a 40 lb bag of that product Quikcrete nearby (there is one about 60 miles away at a hardware store) . There are 10 lb pails of it available locally (or course, much more expensive)
    My sauna hot room floor is about about 47 square feet. I am planning on using your Durock/Quikcrete /sleeper/skim coat method of creating the hot room floor.
    I’m guessing I’ll be moving on to that phase of construction in a week or so, but trying to access my materials now. I’ve got the Durock/wafer screws and 2X for sleepers no problem.

    Can you give me a guesstimate on how much Quikcrete mix I”ll need for this if possible?

  48. Hi Maureen,

    I’ve done this project more than a dozen times, so my guesstimate for you should be close. For a 6×8 hot room, 48 sf., i’d be using about 3/4 of a 40# bag. Vinyl Cement Repair. It may be called something else in your neighborhood, but this is what you want.

    Please take note of how it is detailed in Sauna Build Start to FinnishSauna Build Ebook, which includes some critical instructions including:
    1. Sponge wet your cement board.
    2. Mix well, like an English milkshake. (I like the double bucket back and forth method, as the good stuff will want to settle to the bottom).
    3. Work into the corners, and along your drip edge, and trowel with the cement board as your guide.

    Hope this helps,

  49. Thanks for the quick reply, Glenn! I managed to get two pails of Quikrete Vinyl Cement repair, totalling 40 lbs. Next step is electrical and insulation, but after that’s completed, its on to the hot room floor. In good sauna building tradition, have just finished closing in the shed exterior today, and the fine weather has ended today. Looking forward to having first sauna around…..mid December….hopefully!

  50. Maureen:

    That’s so great! I can totally relate. As I think about it, I’ve undertaken most all of my many sauna builds during this same fall time of year. In the spirit of good sauna building tradition, it’s such a warm feeling to have the building completed, then the weather outside can become frightful, as we focus on the interior.

    I particularly like how after insulation and foil vapor barrier, our saunas can actually be warmed by a light bulb. Precursor of great things to come.

  51. 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!

  52. 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.

  53. Is there a concern when nailing your T&G cedar that the holes in the vapor barrier behind the boards will allow moisture into the walls?

  54. Brett,

    I know, right?

    Moisture is lazy. It’s like a teenage son getting ready for school. But given the right motivation, it’s out the door fast. What this means is that opening the door from a steamy hot room to a cold dry winter’s night, woosh, moisture movement like crazy.

    Yet tiny pin holes leading straight into wall joists..well, there’s really no way, and nowhere to go. Moisture will only permeate if there’s an easy path. And there’s no path. Moisture doesn’t much get behind our paneling. And the little that does can’t get through tiny nail piercing. If moisture could travel through the nail piercings, it can’t go anywhere as foil is sandwiched tightly to wall joists.

    So, that’s how I sleep at night. Teenage son dashing out the door, but not sneaking around.

    That said, there is the sauna design concept of insulation -> foil -> firing strips (air gap) -> t&g. This method gets away from foil nail piercings. There’s a lot of argument pro and con air gap, more questioning if foil is doing its job without an air gap than nail piercings. And all this is valid and comes at the minor expense of a tad smaller hot room, and how to deal with “cleats” or supports for our benches.

  55. 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!

  56. Hi Glenn,

    This seems to be a rather successful method, but I am still wary of using it in the sauna that I’m building because I have a shower and spigot plumbed into my steam room. Is the amount of water this method can handle enough to run a shower onto?

    If I can use it, with some board running up the walls, do I tuck my foil vapor barrier over the top of the backer board to allow for smooth water flow, or do I install the backer over the barrier which runs to the floor.

    I have loved reading your humorous posts as I give life to my first sauna.


  57. Jonah:

    Glad saunatimes is working for you.

    Regarding considering your situation, I think it a good idea to think like water. And think like a contractor building a shower. In this case, contractors install a “pan” and “red guard” the floor. It’s a bigger hammer than the skim coat cement board method, and may be the right step up for your situation, where a shit ton of water is going to flow, with a shower in your hot room.

    Also, generally, foil wants to be behind everything, interior wise, but on top of your studs. Kind of like lettuce to your sandwich. This is the kind of thermal moisture break we’re looking for.

    Good luck on your project, Jonah! We’re with you in steam and spirit.

  58. 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.

  59. Hello:
    enjoy the site. What can I use for a to protect sill plate from rot in my indoor sauna placed on concrete. I do not want to use pressure treated as I’m concerned about off-gassing. (Or I’d PT ok?)

    Thank you

  60. Spencer:

    Sill plate for indoor sauna: I’d use pressure treated. The sill plate is buried by foil vapor barrier. And matter of fact, I recommend 2x pressure treated stock for drip edge. I know it’s janky to be thinking this for a sauna hot room, but 1) it’s way down low and doesn’t get warm there, and 2) very little is exposed.

    In my book you’ll see how I recommend treating where wall meets floor, and to me the benefits of pressure treated for this one spot is well worth the very minimal jankiness. And my wife and I are very free range organic types.

    If above doesn’t give you the total confidence, and I respect if you’re still not on the reservation, well, you could use 2×4 cedar as bottom plate.

  61. Hi Spencer,

    Another option, if you can find a mill that has it, is to use black locust. It’s more rot resistant than PT, and it grows prolifically, but not many mills work with it. Still, if you start calling local independent sawmills you may well find someone who has a bit around, and you don’t need much for just the bottom plates.

  62. Hi Mitch,

    You can do this and i’m thinking all will be fine. I’ve not had any vinyl patch cracking in many years of doing this method.

    One thing you could think about is some Great Stuff! squirts between the Ben Squares, then lay down the durarock or plywood. Adds support there and a clever use of that product. Friends have done this to help support the floor and de sponge ify and it’s been very successful.

    I’m not up to speed on shluter ditra matting, and I may fire up the Googlator to learn more. It sounds like a cool name for an art movement or Mosiac IPA from Northern BC.

  63. Hi Glenn,

    I am in the process of a sauna build in northern BC. Wondering your thoughts on a plywood sandwich floor? The foundation is on a deck of 2×8 treated joists. I am thinking:

    – 3/4″ Ply on the joists
    – Sleepers in Ben Square method with 1″ as the smallest height
    – 1″ XPS Insulation between sleepers
    – 5/8 Ply on sleepers
    – Waterproof the ply with a product like Mapelstic
    – Duckboard on top

    This gets rid of the vinyl patch and the durarock. My concern with the vinyl patch is cracking due to movement of the subfloor – have you seen this at all? What about an uncoupling membrane between the ply and the vinyl patch such as shluter ditra matting?



  64. Glenn!

    Have the eBook, refer to and this site daily–stove is in, on pavers, durarock behind w/ mortar, chimney is drafting and room is wrapped. (it’s been fun working in the cold with small test fires, now.)

    Anyhow, I’ve read-and re-read this post a few times and just want to say thanks for including this and the pictures.

    Will be doing this sleeper method tomorrow.

    Couldn’t have built it without your book and site.

    Thanks again

  65. 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

  66. 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.

  67. Wondering if any one has used waterproofing mortar from rapid set to seal their floor? Thanks

  68. Hi Chris:

    No, i wouldn’t vinyl cement skim coat over plywood. It’s not the right medium mix. Cement board and vinyl cement work really well together, like a baguette and a good French brie.

  69. Hi Glenn

    Could you clarify your typical cement to water mixing ratio for the english milkshake? …about 6:1? … or 3:1?

    have yo applied the milkshake with a squigee?

    + any issues with resulting weakness in using thinner mix ?
    (per quikrete’s spec “…to much water (less than 7:1 ratio) will produce a weaker product…”)

    + As Quikrete’ vinyl concrete patcher does not seem to be available in my region, have you used any other suppliers’ products with same success as the vinyl cement? … Sakrete’s Top N’ Bond or Flo-Coat concrete resurfacer or Quikrete Self-Leveling floor fast setting resurfacer? … any recommendations?
    (a bit mystified by the many options! … with or without polymer modifiers?)

    Thanks for your work in supporting DIYselfers!

  70. Patrick:

    1. English Milkshake mix.
    It’s all feel. I’ve become that same guy I used to know: grey hair, garage stereo, whining about the price of things, no measuring devices whatsoever. What I do know is that the vinyl cement mix is thin. And The three bucket method is really the best. As well as you mix your cement, it settles. The way to counteract is to pour from bucket A over to bucket B, then back to A, then maybe B again, and back to A, then pour some onto the cement board.

    2. Squigee.
    Yes, matter of fact. And the squigee does too good of a job (it pulls all the cement away from the cement board). The trowel is the perfect tool. Use that.

    3. Finding vinyl cement.
    Find it. You can do it. It’s the perfect product. All that self leveling jazz is a different animal. As noted above, I’ve become one of those grey hair stubborn mules that locks into something that works really well and doesn’t want to try to fix it.
    This link brought to you by Ace Hardware.. Ace, for all your DIY Sauna Floor Skim Coating needs!

    Patrick: This skim coating business. It really goes fast after you set yourself up for it. Tape the drip edge. Tape your drain. Fill gaps where cement board butts. Wet the cement board (so it’s thirsty for more, not saturated.). Start in the far corner. Trowel fast. Do the B job, not the A job. Some trowel marks help wave the flag of freedom.

    You’re welcome. Happy you are tackling your own sauna build. I enjoy helping fellow DIY’ers! Hashtag: empowering! (it’s all in the book).

  71. Durarock is a brand name. Like Kleenex. Or in your country: Hoover.

    Cement board is the generic term for it. It is exactly this. Cement in a board form. 3’x5’ but not sure the metric conversion. And there is webbing inside the cement board that holds it all together. Hope this helps!

  72. Hi Glenn, we are building a portable sauna in Scotland but struggling to find Durarock, do you know of any other alternatives?

    Many thanks

  73. A system I like is 2″ rigid foam, ripped on table saw at 14 1/2″ so as to set between floor joist framing. You can run some 2×2’s 2″ down inside the floor joists so that the rigid foam sets ‘flush up’ to your plywood.

    This is a great system for creating an insulative barrier for your sauna building.

    It doesn’t cost too much, and we pay for it one time. Then with a good ventilation system that draws fresh air into your hot room, your changing room floor can be that much warmer for hanging out between rounds on cold Vermont evenings.

    I suppose you could use vapor barrier on the floor.. I’ve never thought about that. hmmm..

  74. I just ordered a Kuuma small, and while waiting for it to arrive am building my sauna. It will sit on a pressure treated frame, open to the outside underneath and screened to keep rodents out. I am in cold Vermont, what should I do for a floor system on my 16″ o.c. framing? I am building the frame rugged enough so that if I wanted to move the sauna, I could drag the whole thing onto a trailer and relocate it. Should I use a vapor barrier on the floor?

  75. Glenn,
    I am about to start the sleepers and floor and have been debating about filling the voids with mortar and just read your post above about using Great Stuff and I am intrigued. Hoping that its a bit simpler than the mortar! Just wondering if you just lay one “line” between the sleepers and then lay in your pre-fit cement board glue and screw and let that sort of sandwich the great stuff for somewhat of a fill of that void? As always your ebook and this site have been an enormous help!

  76. fab, Greg.. glad the book has been so helpful.

    This Great Stuff! business between sub floor and cement board, and between sleepers, is a Great Thing!.. And they may just package the same stuff in the same can and call it Great Thing! because it seems as if it were made for this application. It cures and becomes strong, helping support the space between sleepers. Just don’t walk on the cement board after you lay it down and the Great Thing!/Stuff! is wet.

    This is super hard to do, so some guys screw it all down, then come back and drill a hole in the cement board and give a squirt of the Stuff! in there.

    More of a squirt circle of a shot of it, vs. running a line of it.

  77. Hello

    My Sauna is being built on a concrete slab base.
    I am wondering if I can simply place bathroom type tiles onto the concrete?
    Would there be a need for insulation the floor with rockwool etc. Do you think this would make a massive difference? Obvioulsy, adding insulation under means there is a need to have a totally waterproof solution that would be placed on top of that. I don’t have the budget right now for a complicated floor solution.

    Any thoughts?

  78. Greg:

    I’ve had better results with the rough, mortar side up. The vinyl cement glides wonderfully along with a trowel, creating an egg shell thin, perfect covering.

  79. Glenn,
    Getting close, about to lay Durarock but wanted to ask which side you prefer to face up? The rough (mortar) side or the smooth (mastic) side?

  80. Glenn,


  81. Glen,

    Got my shed built and dried in. Next the floor. Planning on using the vinyl cement method from your book.

    Do you first use thinset under the cement board (on the plywood subfloor), on cement board seams, etc? Or do you just screw it down and coat it with the vinyl cement?

    And do you first put a layer of vinyl cement under the paver block stove platform? Or do you just glue them in place onto the plywood and then coat the top?


  82. Hi Glen, essentially the same question as Erik above; I will not be using sleepers as my floor is already slightly sloped towards a drain. therefore, the cement boards will be screwed directly on the plywood. Do I need to use thinset under the cement board (on the plywood subfloor) ? I’m not tiling over and just need a splashproof surface so not sure if it’s really worth it. Let me know what you think. Thanks.

  83. Hi James:

    I get a handle on your project. When you say root cellar with a chimney, it is clear to me. We want to be careful here. Stone is an excellent conductor of heat, which sounds nice, but it is a buzz kill when considering about how it will be sucking infinite amounts of heat from the Kuuma into the walls, where it will be lost forever into the earth.

    If it’s not too late, I would be thinking of applying one of two major construction design elements to this project:
    1. 2″ rigid outside the concrete and under the concrete floor. or
    2. Firing out your concrete with 2×2’s, filling joist cavities with rigid insulation, then polyiso over the entire area, then firing strips, then paneling.

    With either #1 or #2 what is critical is a thermal envelope separating the stone from the hot room.

    #1 is less desirable as all that stone has to get hot before the sauna will get hot.
    #2 sounds like a drag, but this is how we do basement saunas with an exterior wall.

    Think of a cold Maine winter’s day and how this stone will want to stay as cold as the earth around it. Even with a Kuuma, you are dealing with a little engine that can’t.

    We have to insulate the stone.

    This sounds like a wonderful project with great outcome, but please talk to others about this before advancing.

    Talk with cement contractors who lay down in floor radiant heat. This is the avenue you’ll be going down. Isolating the concrete.

    Hope this helps James!

  84. Hello Glenn,
    I just purchased your book and looking forward to checking it out.
    We are about to start construction on our second wood fired sauna. Step one was to purchase a Kumma stove.
    It will be here in about 6-7 weeks. We live in Maine so the timing is good.
    This sauna will be different in that we are building it into a hill and will be covered with earth. All concrete. Think root cellar with a chimney. The sauna room will be 9×9 and the ante room 6×9. A stick framed wall between. The front door area will be stone facade with a pergola over. All white cedar inside.
    It will have a concrete floor w drain. 1. I’d like your view on insulation 2. Cedar grating sections for floor.
    Thanks. I’m grateful for your insight. James Buchanan

  85. Hoping you can answer my question! I recently purchased a used barrel sauna. The wood has some holes and cracks in it and I have been exhausted trying to research how to properly seal the wood without having to replace it. Could your method be used on the outside of the barrel sauna? I appreciate any feedback!

  86. Instead of calking or filling the cracks, I think you will have better results creating an envelope on the outside of the barrel. Roofing material is the simplest method. If you type “barrel sauna” into the search bar on google and hit “images” you will see these jackets or roofs atop barrel saunas.

    Doing this, in my mind, is better than sealing the holes and cracks. Any sealant, as good as it may be, will be poly and petroleum based, and potentially yucky with lots of heat. And more than that, the sealant, being different composition than the wood it is trying to bind to, will expand and contract differently than the wood, and be prone to separating and failing over time.

    These are my opinions, Mollie, and hope this helps/inspires.

  87. A quick question. I’m getting ready to do my floor. Are you considering the 2×6 to be the “drip edge”? I assume the 45 degree angle in facing up so the T&G rests on the angle? Then, durarock up to the face of the 2×6 and seal the small gap between the 2×6 face and durarock with vinyl cement?

  88. Hi Sam,

    Yes, the process for the drip edge is detailed in the ebook. I like to rip the 2×6, creating 2×3 stock for drip edge. And you got it on the 45° “chamfered edge” as the pros call it.

  89. Hi Glenn,

    First off, thank you for this website which has been an invaluable source for my research during my sauna build, and a steady reminder to relax and enjoy the process with some laughs and beers.

    I am currently ready to put a floor into my sauna; this point in its construction that has been seeing delays because of my uncertainty surrounding waterproofing. My intention to install a shower and worries about water compromising the structure of my investment have me focused on preventing water from going anywhere but down the drain. So at this point I have arrived at your tried and true vinyl patch skim coating method after much deliberation over installing a tile floor and other options. With that said I have some questions that I am hoping you can answer which have been partially addressed in this thread already. If you can provide any insight it would be much appreciated. Thank you for your time and consideration.

    With the shower stated for installation inside the sauna room I feel the need to ensure the floor is adequately waterproof. Especially with the sauna needing to withstand the heat and wet as well as temperatures exceeding -20c. I have seen you mention that the vinyl patch is waterproof as is but also told Jonah above that something like redgard might be smarter in applications involving showers. I am having trouble figuring out if the vinyl patch will bond to redgard (or vinyl sheet material often used as a shower pan) and therefore am not sure if I can get proceed with your skim coat method by simply adding redgard or vinyl on top of the durock. I was tempted to put redgard or vinyl sheet (conveniently I have much of this from the old pool liner) underneath the durock instead, essentially as a backup if any water made it through the vinyl patch but I realized that would mean screwing through the “pan” and I’m not sure that that is wise. So, this leaves me thinking maybe I should just do multiple layers of skimcoat and monitor for cracks going forward, or add a layer of rust-oleum epoxy like Mark above, or use another product like a waterproofing mortar like others have suggested.

    Long story short I am graciously wondering if you have any suggestions for me to ensure my floor is waterproof enough for a shower to be in the sauna room which is on a plywood subfloor that is screwed down to sloped (for drainage) floor joists.


    I tried to be succinct, sorry for the long comment.

  90. Hi Marshall:

    Glad you are digging saunatimes.

    The hot room floor tried and true method you reference works great for most sauna applications, where “rinse offs are strictly an outside affair.” If you are going with a shower in the hot room (more on that below), then I would prepare your floor by following the bigger hammer methods you reference, like preparing your sauna as you would prepare a shower stall. These methods include a shower pan for the floor, red guard, etc.

    Now, here’s where I apply my Sauna Cognition Theory and try to persuade you to not put a shower in your hot room. A sauna heater isn’t made to withstand all that moisture produced from a shower in the hot room. And the pores of your skin and your wood lined walls will appreciate your shower action out of there, in cooler air.

    But your sauna is your sauna and I’m not trying to be a dick about it. Sauna on Marshall!~

  91. Hi Glenn,
    First-time sauna-builder here, My question is – when applying the vinyl cement to the durarock, is there a correct “side” to do that on? One side of the durarock seems smooth, and the other more rough. I’m curious if it makes a different to how the vinyl cement adheres…
    Thanks Glenn, your website and e-book have been a huge help through this process!

  92. I am curious? Why cant i have my entire room finished with cement board and just have my seats done in Timber.
    Is it because of the mold? Coz as long as i am willing to not touch my wall and wear bath slippers… what could go wrong?

  93. Nothing can go wrong. One could argue that the heat up time could be longer, but I like the concept of lämpömassa producing material like cement board. I just got back from Finland, and it is not uncommon for saunas to have cement board as the ceiling.

    I love the idea. If you advance with it, please email me.

  94. Hi Glenn,
    Thanks for all of your amazing info and publication-
    I am building a 5×6 sauna in the corner of a cabin. The subfloor is advantech, which is a very sturdy OSB material. The tricky part in my build is that this corner of the cabin is over a crawlspace for the mechanicals so there is a trapdoor in the floor. It can’t be moved, so I have to figure a workaround- I would not be able to pitch the floor, but was debating doing a skimcoat and letting stay heated for a bit and dry out after every use. I also considered a rubber mat under duckboards that I could lift up if I needed to access the hatch, but I’m a little worried about moisture trapping under the mat.
    Any thoughts on how you would manage this?
    Also, if I go with skimcoat do you think i could apply this directly to the wood subfloor or would I have to put cement board down to the subfloor first?

    Thanks again!


  95. Hi Glenn,

    Thanks for your input and very fast reply. I never thought you would get back so quick so I’m just checking now.

    I have decided to go with a deck waterproofer, which the manufacturer says will do the job so I should be able to apply the coating direct to plywood and then add duckboard where needed on top.

    I’ve spent much time trying to convince my parents whom I am building the sauna for to keep the shower in the change room/ vestibule, but moving the shower to the middle of the sauna room was a compromise I’ve had to make. Sauna cognition theory has me contemplating lots of life decisions, hopefully the ones I’ve made, even in compromise will result in a kick ass sauna! Would love to make an article on sauna times about my build if all goes well.

    Hope you’re having fun in Finland, been checking out a lot of your youtube videos!

  96. Hi Marshall…

    I hear you. I learned long ago that when my parents have something in their head, to not try to change their mind, but work with it. If you are going with a shower in the hot room, and that amount of water in the hot room, I’d consider the floor of your hot room to be a shower stall, and build the floor to that standard. I’d gravitate away from waterproofing (or attempting to waterproof) plywood, and move right over to cement board and tile or skim coat seal the cement board. I would rip 6″ lengths of cement board to use as drip edge and apply around the entire perimeter of your hot room, to create a water proof pan throughout your entire hot room floor. Maybe even higher up the wall, acting as a knee wall splash guard.

    Water will splash around and want to collect along where wall meets floor. Dish pan it. With drain. I own a corner trowel and it’s a great investment.

    You got it, Marshall. Yes, stay in touch on guest post. Take good pics and keep the Sauna Cognition Theory in front of you.

  97. Haha, that is something I’ve learned during this project. I spent MUCH time trying to convince to keep the shower in the vestibule where I designed it to be but the powers that be said it was not to be. Thus, here I am trying to waterproof my sauna floor to a higher spec.

    Thank you for the details on waterproofing, I really like the idea of using skim coating on cement board, and especially to use it coming up the wall which not only provides the benefit of water sealing but also reducing cost when compared to cedar tongue and groove on that invisible part of the wall. The reason I said I am going with the deck waterproofer (it’s called tufdek rubber deck coating by Ducan) is again because of a parental discretionary decision. I have been pushing for your skim coating method, but my father’s experience with Durock is that it has a noxious smell that he now refuses to work with. I have not worked with any cement board before myself so I was surprised to hear of this issue. Especially when I have seen you say in other threads around your website that you like the idea of exposed cement board walls and other people have used exposed cement board in multiple scenarios. So if there was a terrible smell to worry about I would not have expected to see cement board in these applications. With that said, I mentioned your recommendation to my father and he has looked into whether there was a cement board he did not find this issue with, and apparently Hardiebacker may be it. Do you have a preferred brand of cement board that doesn’t have a smell or one as bad as Durock supposedly does? Maybe it’s just him but that’s the main thing that has kept me from cement board skim coating to this point.

  98. Hi Glenn
    I see in 2018 Asaph asked for photos of the duck board. Your ebook describes how to build but I dont understand where you use the 3/4 inch by 3/4 inch pieces. Do you have a photo to help illustrate how to properly build duckboard including proper placement of the 3/4 inch pieces?

  99. Hi Todd:

    The duckboard design I like most is the simplest. If your cedar boards are 3/4” thick, then you can tie them all together by double nailing two ends, top and bottom, ripped to be the same depth as the thickness of your boards. That way everything lies flat against the cement floor below. And these boards are best to be 3/4” by around 3/4” so you can nail them into place. You can make a few of these duck board pallets and lay them down in your hot room so it’s easy to pull them up for cleaning.

  100. How do you set the stove on top of a pitched floor? Basically how do you level the stove? I have a salvaged science lab countertop that I plan to put the stove on. I was planning on doing a concrete slab under the stove with lab top on top of it and then the rest of the space I would apply your pinwheel technique or maybe the Trevor method, i haven’t decided yet. I plsn on seperating the stove floor from the rest of the hot room. Have you ever incorporated a shower pan liner into your projects? I am kind of concerned that the plywood subfloor is going to wick moisture from the dry packed mortar, use some sort of waterproofing or layer between?

  101. Charlie:

    Stove atop a pitched floor: please note all the details in my ebook.. Pavers.

    Shower pan: yes, i’ve done this. Especially for indoor projects, where the tolerance for floor leaking is zero.

    My ebook outlines the way to seal off our floor, it’s worked great over decades, but may not be the absolute for all applications.

  102. Is there a reason you wouldn’t treat the sauna floor as a nice shower floor and just tile it on top of the dura rock? Is it a matter of cost and time that people don’t just tile the floor?

    Can anyone point me to this ebook for the build?


  103. Hi Rick.

    Tile is sure a positive move. For many, tiling is 200 level action, and requires some additional tools that the amateur DIY’er doesn’t own. But it’s sure a good thing to tile and drip edge. yes.

    One thing, tiling a mobile is not usually a good thing. Lots of bouncing around. The vinyl cement seems to offer just enough elasticity (without need for spell check).

    here’s link to the ebook.

  104. Thank you for the response, I will likely go with tile as this will be a permanent structure. Looking forward to reading through the ebook! What is meant by “200 level action”? I’m no expert but I’e done tiling and have a tile saw etc. and above all, TIME.


  105. Hi there, I have an existing shed that I would like to convert into a Sauna. Is there anyone around the Georgian Bay/Midland Ontario that could help us with this job.

  106. I live in Gravenhurst ad build my own sauna. To convert a shed into sauna looks like an obvious option. However, there are a lot of factors involved and to consider, if you aim at a quality sauna. Basically imagine, you want to build a tiny house according to local building by-laws. Following those by-laws will help to protect your investment and guaranty the health of the building, starting with the (rot-free) floor. To say any more specific is difficult, because we do not know how your current shed is build. If you like to visit us, to see our garden shed sauna, for inspiration, you are welcome.

  107. Hello again. Outdoor sauna. 8×13 footprint. 8×8 sauna and 5×8 changing room. In process of building on post foundation. I’m using 2×8’s for the floor joists, building a french drain centered in the 8×8 square, and the whole thing will sit about 4 inches above the ground. Floor base over joists will be 3/4 treated plywood. QUESTION: Should I insulate below the floor or provide some type of protection underneath? All wood is treated but this needs to last for years. It won’t have grass growing under it, it will have a bed of rocks etc. Just concerned about long term wear.

    If I insulate that means I need to build another cavity within the 2×8 space. I wouldn’t want a moisture trap. Is his unnecessary engineering. Thing is once it’s built there is not accessing underneath.


    Thank you!!!!

  108. yea, we can wrestle these thoughts to the ground. I like rigid insulation ripped on a table saw, cut to fit between floor joists, flush up. It’s a good gig, and creates that thermal envelope. And critters generally don’t like the rigid insulation.

  109. In the picture showing the cement boards being installed it looks like there is aluminum flashing at the bottom of the wall.

    Is it recommended to install flashing on top of the cement board?

  110. A guy can do this. what’s good about the cement board is that it’s a lämpömassa enhancement. Stone, absorbing the heat from the stove and providing some latent “ahhh” for the hot room. I don’t think it’s critical to have metal flashing, but as detailed in my ebook, the drip edge is a must have for hot room, where wall meets floor.

  111. Hi Glenn, I was hoping for some clarification on the drip edge installation. My logic is saying that I should install the foil barrier on the wall, then durarock upto that…THEN install the drip edge on top of the durarock and vinyl cement up to the drip edge. What am I missing? I know there must be some reason you do the drip edge first but I just can’t work it out.

  112. Jason:

    Drip edge first. Then cement board.

    The advantage is that as two mediums meet, you’re breaking the mediums via the drip edge.
    Wood walls expand and contract a bit differently than cement/stone.

    Like British diplomacy, we like to separate the two and yet help them work together, but save the gin and tonic for round 1.

    While you’re at the subfloor stage, if you screw in your drip edge to the base plate and floor joists, you establish a line of difference and moisture defense. Then, Butt up the cement board to the drip edge. Then blue tape your drip edge and vinyl cement against the drip edge.

    Then, as you apply paneling, you can set your first course of paneling on top of the drip edge. (and you’ve chamfered the top face of your drip edge to deflect any water running down your wall. If going air gap, you’ll put in spacers atop your drip edge and roll your first course of paneling from there.

    And yes, sandwiching your foil behind your drip edge ensures a hermetic seal there.

    The drip edge is a great way to roll, as you know. And this is an easy, effective way to separate the mediums.

  113. Hi Glenn, I’m wondering what you think about applying skim coat directly onto a primed plywood subfloor and just manually sloping the floor towards the drain by eye. This seems like it would take up a fair bit less vertical real estate and would require alot less fiddling with thin slices of wood.

    What downsides do you see of doing this method? Do you think its a feasible route?

  114. I’m a bit concerned about the pressure treated drip edge off-gassing in the hot room. Do you recommend making the skim coat layer completely cover the drip edge?

  115. Adam,

    If this is a concern, you can use a different material, or paint the pressure treated. It’s relatively cool down there where wall meets floor, but I feel your sentiment. If there’s a better material to use for drip edge, I’d like to know about it. Cedar and any other material “wicks” moisture.

    I know that some have cut strips of cement board to use for drip edge. And this would mean using a corner trowel for sealing off the drip edge. I think this is a great idea possibly for you. But you can let us know how it rolls,

  116. I like your thinking Adam, yet i’d shy away from this. the skim coat material and wood can hold together, but I think they’d separate over time. The vertical real estate is compromised by the thickness of cement board/Durock which is 1/2″ or 3/4″ depending. I really like how the vinyl skim coat integrates with cement board.

    The issue is layering the cement with a trowel is that it’s really hard to work with it. If you skim coat the cement firmly and evenly against the cement board, it goes on really evenly.

    I hope this helps you.. you’ve got good logic going with your idea, but i think the cement board will help you in the long run.

  117. Building my first sauna. Started researching when it came to the floor and ran across your site. I did the Ben square method with sand mix quikrete in between to fill the space for a solid floor and durock on top. Instead of the vinyl quikrete I wanted a nicer finish so I used the quikrete Re-Cap which is a resurfacing polymer mix. Quite a bit more expensive at about 35 dollars a bag but it came out super smooth like finished concrete. Really happy with it. Just thought I’d pass this along. Hope to be finished and sweating in a few days! Thanks for the site! Very useful

  118. Quick question that I can’t find an easy answer to: I’ve finished framing my sauna with a hot room floor of 6×7. I plan on using the Ben Square method with a slope to the drain. Here’s my question: will the duckboard sit flat over that span of a sloped floor? How do you keep the duckboard from being uneven or bending above the lower drain space? Am I overthinking this? Is it strong enough to support humans without sagging? Thanks so much! Your ebook has been invaluable!

  119. Hi Cullen:

    A tad overthinking here. Duckboards are easy to build. Try this:
    Go to big box store
    source a few cedar fence pickets… clear minimal knots.
    Rip these on a table saw.
    Rip a couple sections 1/2″ x 1/2″ – these become your headers to secure the slats top and bottom with a couple finish nails in each.

    That’s a simple way to make duckboards.. and they are all one plane. One dimension. The lay flat over your floor, and the weight is supported ever present everwhere.

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