Thought I'd share my recent "urban" sauna build. The cedar panelling, benches, doors, windows etc are all made from re-purposed materials salvaged from a cedar deck that was well past it's useful life. This is a combined tool shed/sauna, with a footprint of about 10 x 14 feet. About half (7x10) is sauna (dressing and steam room) .

The old decking was severely weather checked and covered with peeling stain, so I needed to get it down to fresh wood. I do own a surface planer, but it would have been dulled very quickly, so instead, I surfaced the wood with my table saw outfitted with a cheap 7 1/4" construction grade circular saw blade which cost me about $10. No biggie if I hit a nail. 

 

 

First step is to edge the boards.  With the blade all the way up on the saw, I can only cut 1 1/2" deep, so I will have to surface the board in two passes. 

 

After getting the board edged on both sides I set the fence to 11/16", and ran the boards through vertically.

 

 There you have it!  Cedar panelling! No it doesn't have tongues and grooves, but I will add a layer of black poly sheeting behind the boards so only black will show through the gaps.  I ran out of long boards, so I used short boards for the benches.

 I ran out of my reclaimed decking, so for the dressing room (photo below) I used 5/8" cedar fence pickets from Home Depot. 

  

  I kind of liked the rustic look of the decking in its original state, so I used it for the dressing room side of the doors.  I also made my own windows by building a simple frame out of thicker material, routering out a 1/2" rabbet, and gluing a piece of glass in with Lexel caulk.  I added a "grid" to the outside for decoration.

 

Other than the framing materials, roofing, and siding, the only costs I had were for fiberglass insulation, plastic sheeting, a few 2x4's for benches, some OSB for the floor (I used tapered shims on top of rigid foam to create a slope to a shower drain), and a small sheet of vinyl flooring for a steam room floor. ) Of course I happened to have an old cedar deck laying around!