I have decided to build (install a pre-cut sauna) in a room in our basement that has a dirt floor. Room size is roughly 7’X7’. Because it is older clay block basement, I plan to add vapor barrier from top of block down covering floor. Same process that would be used to encapsulate a Crawlspace. I have dug out and leveled dirt floor to all or for 2” of HD EPS foam. I originally planned for a concrete floor, but I will need less than a yard and have been having a difficult time finding someone with a mini mixer. I have little desire to mix 15-20 bags in basement by hand. Since I am planning on putting tile down, can I double up on 1/2 or 3/4 plywood, then put down a tile backer and tile or is this asking for trouble? Everything would be inside of the vapor barrier... Thanks in advance for your thoughts. Ian.

You can't find an equipment rental? Even at your own local home depot?

Exactly my thought too... Are you asking us to condone laziness and doing a hack job? Just do it right. Remove enough of the soil to get your desired finished floor to ceiling height, place a couple inches of gravel, place vapor barrier, pour reinforced concrete slab, place tile membrane and then tile the floor. But save the labor of mixing bags of concrete...bring in a concrete truck and pump... And maybe put PEX in slab to provision for possible future hydronic radiant heat to create a comfortable space.

I agree with my friend sailawayrb. Your going to the trouble of building a sauna and your setting it on dirt. This house must have cellar windows or an old coal chute. Mix your bags outside and either bucket it in the cellar or make yourself a chute.
If it takes you an hour to mix 20 bags I would be amazed.

Thank you for the responses. I can assure you the intent of question was not out of laziness.

I have been unable to find someone to deliver such a small pour, so planning on renting a mixer.

Thanks for the input.

You really don't need a mixer. I've mixed a lot of concrete by hand. You need a wheelbarrow, hoe, shovel, bucket, and some kind of float to smooth out the surface.

Thanks Smartwall!

I finished the 20mil vapor barrier on walls, will be putting down the EPS and vapor barrier on floor today.

Possibly ready for concrete tomorrow.