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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?

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 cement board. We can set sleepers two ways:

  1. The bicycle spoke method
  2. The Ben Square method.
bicycle spoke method of sloping floor drain
Ben Square method: glue and screw sleepers at decreasing widths to drain

Either way, we create a slight and gradual slope, so that when we glue and screw down durarock, 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 trowel guide to ensure a smooth finish. Run a wet sponge along the sleepers so that durarock can lay flat.

laying in mortar mix between sleepers

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

sloped cement board supported throughout
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.

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9 thoughts on “Looking to pitch your sauna floor and install a drain? Consider the Trevor Trowel Fill Method”

  1. ok Glenn, i JUST left a comment on a different blag about DO I REALLY NEED A FLOOR drain? well, i think the time has come that i CHOOSE to trust your experience and wisdom with this stuff. my question is this, is the dura rock and vinyl cement repair flexible enough that i wont crack when the trailer flexes during travel? Should i consider using a epdm or rubber shower pan material over the dura rock instead of the vinyl cement repair method? if you say that the vinyl cement repair skim coat is the best way to go, can it be dyed black so it wont be too noticeable under my duckboards?

  2. the above comment should also include: Im building a mobile sauna so weight is a consideration, the ‘sleepers with fill’ method would get pretty hefty. whats a comparable method that isnt too heavy?

  3. Hi Barrett: For mobile, we have a very clear, optimal solution for hot room floor. No need to pitch our floor to the drain. Instead, we do this: we red guard our wood subfloor OR durarock/vinyl cement skim coat over our subfloor and punch in two drains: one in the back corner driver’s side and the other in the far corner passenger side.

    Ever so slightly, we pitch our trailer so water drains to the back, and Murphy’s Law works in our favor as the trailer will pitch left or right 98% of the time, and it need not be much.

    Mobile Non Level Activation works in our favor. 🙂

  4. I like the durarock / vinyl cement repair team. I’m just a nut that way. It’s worked great for me for decades. In mobile, I’ve become quite open to the rubber floor mat solution (for weight and twisting and turning). So, you’ll do the right thing, i know it. Send me a pic, and let’s see how it rolls for you, Barrett!

  5. I am currently under construction on a basement sauna. I have plumbed in the drain for shower in the changing/relax room and a drain in the hot room floors. I am looking to slope the floor in the hot room as the floor is level. would you recommend the above example for sloping an already existing level cement floor? (I already purchased your book and it really only covered sloping wood floors in outdoor saunas) . How have you sloped an already level, cement floor in the past? Thanks

  6. David: Yes, for sure. I have dealt with an existing cement floor, to create a slope for drain. Before advancing in any direction, I’d contact a cement expert, someone into more of the nuances than the typical square peg, square hole cement contractor. Because an expert may suggest “scoring” your exiting cement slab, to make it rough, and able to accept an overcoat or top coat that you’ll pour and trowel atop existing slab, to create the slope.

    And another expert may say “don’t bother, you’ll get dust everywhere” and will point you in the direction of a good cement patch product and say “them are good for sticking to existing concrete.”

    First thing i’d check is: is your existing basement cement floor really level? I’m betting that it’s not. There may be an existing slope away from your exterior wall, which may work in your favor. Not seen to the untrained eye, but very trained for water which always seeks its lowest level.

    Second thing to keep in mind is that that if you do need to slope your floor to drain, your run is very short, and so you’ll need very little build up along your walls. So, if this were my build and I needed to create a slope to drain, i’d:
    1. be using 2×4 green bottom plate for my hot room walls.
    2. run a bead of silicone underneath my bottom plate before cement screwing it to existing cement slab.
    3. screw in a drip edge (as detailed in my ebook) with a bead of silicone underneath.
    4. run another bead of silicone along inside edge of drip edge, where it meets the existing slab.
    4. mix up some vinyl cement or recommended cement patch product and trowel it nicely along the perimeter of my hot room, with gentle slope to my new drain.
    5. rinse off my tools and crack a beer.

  7. Glenn-

    The floor is surprisingly level. I put a 4′ level to it and dumped a little water on it. it doesn’t run, just sits there.

    You mentioned you have applied a slope to an existing cement slab in the past. How did you go about this and were you satisfied with the results? Thanks!

  8. David: Yes, i’ve created a pitch to an existing flat slab a couple times. I’m pretty sure I used vinyl cement repair. 40# bag, which was more than plenty. I troweled it over the slab and up against the drip edge around the perimeter. I’m trying to remember if I did anything fancy to the existing slab, like acid wash the paint or score it in some way to accept the vinyl cement. My take is to ask a cement guy what he’d use, so that the new pour adheres to the existing slab.

    It’s easy work, i mean, it should only take you about 20 mins. once you figure out the best product to use and the prep involved.

    And you’ll most likely have a cedar duck board atop your hot room floor, so any trowel marks, etc. will be hidden.

  9. Thanks Glenn. I think I will do as you recommend and just use the vinyl cement. Will definitely use a bonding agent between the 2 pieces of cement. The floor is larger side (8×7) so I will probably put down some pressure treated kneeling strips to keep me in the proper slope.
    Thanks again.

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