The interior of our sauna hot room is designed for the maximum sauna experience and safety. Cedar clad walls and ceiling fabricated to provide an even flow of löyly for users and a sloped tiled floor complemented the stone wall near the sauna stove.

A wall separating the sauna hot room from the changing room was constructed with openings for the future candle window and sauna door. Since this was a non-structural wall I used some of  the cedar 2"x4" I salvaged from the deck rails. Might as well put it to use for something!

(View is from the changing room looking into the sauna)

We lined the exterior walls of the sauna with 3.5" thick x 15" wide, R13 rock wool insulation and the ceiling with 7.5" thick x 24" wide R30 rock wool insulation. (We had planned on using 5.5" thick R23 in the ceiling but it was not available. The R30 was actually less expensive per square foot and gave us additional insulating value.) 

Rock wool insulation may cost more than fiberglass insulation but it is heat resistant to 2000° F. and also very moisture resistant. Heat and moisture are two of the major elements of a sauna so we felt it was a worthwhile investment.

We used what insulation we had left to insulate the wall separating the sauna and changing room. We don't mind if some of the heat from the sauna escapes to heat up the changing room in the winter. 

(4) 12" x 24" x 2.5" thick pavers were glued to the floor to provide a 36" square solid base for the sauna stove. The arrangement of the pavers left a 12" square hole in the middle which was filled with a 12" x 12" paver (I couldn't find one the same color but it will be hidden under the stove and actually accents the tile wall and floor tiles nicely).

I originally was going to use two layers of pavers to provide a 5" high base but I wanted to cut down on the weight in this area. We still have a +400 pound sauna stove to sit on this base!

After the walls and ceiling were insulated they were covered with an aluminum foil thermal and vapor barrier to help reflect heat back into the sauna and protect the wood framed structure. All seams were taped air tight with heat resistant aluminum tape. 

We were scared that the foil would rip easily but it actually was quite durable. This foil was 8 mils thick, 4 feet wide, and had 250 square feet per roll. About $50 per roll on Amazon.

6" high cement board was installed around the perimeter of the sauna room floor as backing for the floor tile around the perimeter of the sauna.

In addition, cement board was installed on the walls as a backing for the stone wall which will act as a non-combustible material for the area near the sauna stove. The seams on the cement board were covered with mesh tape and then flat troweled over with a thin set grout, as were the screw holes to provide a flat surface for the tile.

To provide a non-combustible wall adjacent to the sauna stove we installed 12"x12" porcelain tile on the walls near the stove. These two walls were 3' wide and 7' tall. 

As with many part of this project, installing tile on a wall was a learning experience for us and it didn't happen without its frustrations. On our first try we completed installing 75% of the tile on one wall but  being laid level and we had issues with our gap so we tore them all off and began again. The second time around it went a bit better. Live and learn.

The grout was also very fast setting so it hardened in the bucket and on the tiles extremely fast. Note to self: Do not use a fast setting grout when tiling the sauna floor!

We cut the 12"x12" porcelain tiles in half and placed the 6" high tile around the perimeter of the sauna floor on the cement board backing material. This will help keep any moisture away from the cedar paneling.

After the cedar paneling was installed we placed a bead of silicone caulking at the intersection of the two.

A sloped concrete floor was poured (2" height at the sauna perimeter walls sloping down to 1-1/4"" thick at the floor drain).  This floor was not as thick I had originally planned for due to reducing the thickness of the stove base. I am hoping that we will not experience any cracks in the floor.

The photo shows how I created a 2" thickness at the perimeter and then sloped the concrete to the floor drain. Again, I am not a concrete finisher and it didn't come out perfect, but it will be covered with tile to hide its imperfections.

In hindsight, I probably should have raised the floor levels at the far corners to give the floor a bit more slope towards the drain.

A floor drain was installed and connects to the French drain below.

We wanted a tile that wasn't slippery when wet so we chose a tile that had a lot of irregular shapes to the stones. The grout in-between the stones also helps it not being as slippery.  The tile also had to have a flexible backing to allow it to be installed on the sloped concrete floor.

Again, this project ended up being more difficult than we thought it would be. The mosaic tiles came in 12" x 12" sheets which were supposed to interlock nicely but we could see the seam and so we had to pull individual rocks out and replace them to try to make the seams less visible.

We laid the tile sheets on a thin set mastic, sealed the stones with an enhanced sealer to darken the stones a bit, and then applied grout mixed with a grout booster in place of water to eliminate the need to seal the grout. 

The interior walls and ceiling  of the sauna hot room are clad in 4" wide tongue and grove white cedar purchased from Superior Sawmill, in Trenary, Michigan. We were very happy with the quality of this cedar! There were a few bowed boards and some with knots but we carefully combed through our selection and utilized them when we could.

We found a laser level very useful in making sure each board was the exact height as on adjacent walls.

We had many excess boards left over so I ripped some to make some of the trim work in the sauna. I also sold my excess boards. Total price for cedar was less than $600 !

We used extra cedar paneling (and ripped the tongue and groove off of some cedar paneling boards) for some of the sauna room trim work. For other trim work, we used 1"x4" cedar boards.

Some of the trim work shrank leaving gaps so we removed and reattached them in the spring after many hot saunas had done their work.

To help produce an even flow of löyly  from the stove to the top bench I created a 1'-0" curved radius transition from the walls to the ceiling on the east and west walls. Although this required a lot more thought and effort, it does produce the results I was looking for.

Each of the cedar pieces on this transition had to have a small bit of the back groove removed to allow the boards to make a smooth curve on the support pieces. In addition, I had to carefully trim the wall boards to match the curved ceiling transition (easier said then done).

The construction of the support pieces and trim work is shown below.

I trimmed out the glass block window we had installed with cedar to hide the ends of the tongue and groove paneling. A small window sill was also provided. This window will allow natural light to come in but not allow anyone to see in.

The window trim was also a perfect place to mount a thermometer. We tried two types of bulb type sauna thermometers but neither proved to be accurate with variants from 10 to 20 degrees. I have since placed a spring type thermometer in this location and calibrated it with an overn thermometer. We also use the digital thermometer probe mounted above the Kuuma stove  to give us the temperature on the top bench where we sit.  The digital display is visible through our candle window.

A cedar branch was attached to the wall to be used as a grabrail to more safely access the sauna benches.

I wanted to avoid storing soap and shampoos on the sauna benches so we installed a small wire basket on the wall to store these products. These are in easy reach of the area used for washing.

In the winter when temperatures are well below zero I detach the basket and rest it on the top bench as the shampoo and body wash freeze. They gradually warm up on the top bench while the sauna is heating and are thawed out when we need them.

I used another Japanese Yew branch to make a hook to hang our ladle and back scrub brush on.

A temperature sensor (wireless meat thermometer) was mounted at ceiling level above the sauna stove and can be read through the candle window by people sitting on the sauna benches or positioned so you can read it as you enter the changing room. This temperature reading can also be read remotely from inside our home via a Bluetooth connection. This feature allows us to remotely monitor the temperature of the sauna as it is heating. A high temperature reading can also produce an alarm to notify us of potential too high heat issues.

Since the monitor came with two probes I have since installed another probe a bit lower that gives us the temperature we feel sitting on the top bench (not shown in this photo). The high probe is used as a high temperature alarm.

A 12 VDC power line was routed from a switchable outlet in the changing room in the sauna attic area and then down the wall to just below the top bench. This line was then plugged into a remote controller and a silicone coated waterproof LED light strip which can be remotely controlled to produce any color and brightness to set the sauna ambiance you desire.

We wanted the sauna changing room interior to have the feel of an older sauna changing room so we bought carefully selected materials and accessories plus used some imaginative staining, painting, and lighting features to create the desired effect. 

To complete the floor system and to add to the rustic look of the room we installed waterproof vinyl laminate flooring with a natural pine look to it to compliment that color of the ceiling and exterior door colors.

After this floor was installed I used our left over white washed boards to make the door and window trim and the baseboard.

Just as I am not much of a carpenter, I'm also not much of an electrician, but I was able to mount the electrical boxes, run the wire, and make the required electrical connections. A big thanks to Al Holm for giving his guidance on this phase of the project.

All of the AC electrical components were confined to the changing room as I did not want any AC voltage in the sauna room. I installed a switchable outlet that has a low voltage DC transformer plugged into it and low voltage wiring routed to some LED light strips installed under the bench and in the cooling off area.

Since we needed to provide some nailing boards along the side wall anyway, we added an additional 2"x6" ceiling rafter to allow us to insulate the ceiling and provide proper air flow over the insulation.

This lowered the ceiling a bit, but the ceiling in this room is so high that it won't even be noticeable. We used R30 Rockwool insulation to insulate this ceiling. Maybe it was overkill, but we had some left over from insulating the sauna so we use the rest of it here. We covered this insulation with a foil thermal barrier too.

We put two coats of water based polyurethane on the tongue and groove pine boards before installing them on the ceiling rafters. This will help protect the boards from some moisture they may be exposed to as steam escapes when the sauna door is opened. 

We had purchased a knotty alder wood door installed in a frame from a local lumber yard. Although this was an interior door, we primed and painted the exterior surface and applied polyurethane on the interior face and added a threshold.

A antique looking door knob was installed to complete the look.

The candle window is a central highlight feature of the changing room and provides light for the changing room and into the sauna interior.

The wood of the candle window was first painted black and then had a coat of white wood glue applied to it. While the glue was tacky, white paint was applied to the surface and when it dried the paint "crackled" to provide the desired effect.

The thicker window sill was was given given a few wacks with a hammer and the edges roughly shaved to give it a more rustic appearance before it was also painted.

The tempered glass was some glass shelving I found on Craigslist and it determined the size of this window.

Hanging in front of the candle window is an electric light that looks like an antique kerosene lantern. Initially we had it hanging straight down from it's hook but to provide a bit more light into the sauna room we swung it nearer the window glass and hooked the chain onto an old rusty nail. We may add a flickering lightbulb in it to give it an even more authentic feel.

If more light is desired in the changing room we also provided a wall light sconce on the wall opposite the candle window and above the mirror.

To allow some natural light into the changing room, but still allow total privacy, a small casement window was installed high above the exterior door. The window slides open and has a screen to allow it be open during the summer.

I cut unused pine paneling boards to use as trim around the windows and doors.

We used some of our scrap wood to fabricate a couple of shelves on the wall to store towels, wash clothes, and other miscellaneous items.

Some wall mounted towel hooks were also added to hang used towels.

I had found an antique looking mirror on Craigslist at the beginning of this project that I thought might look good in the changing room.

We mounted a fire extinguisher on the wall just inside the changing room exterior door.

My brother Allyn gifted us a special memento for our sauna: The wood match dispenser that we had in our home while growing up. 

He wasn't aware that I was actually looking for an antique looking dispenser for this sauna so this gift was a thoughtful gesture and completed this project nicely.