Building a Log Sauna, the First Run

With the block wall in place, it was time to start actually assembling beams for the sauna.

Originally my plan had been for three inch thick walls at the sauna, and five inch thick walls for the cabin. When I found a source for much larger white pine, I upgraded the cabin walls to six inches thick. This meant I had a surplus of five inch logs. They would certainly be put to good use as extra sauna logs. It also was a bit of a blessing, in that some of the beams on the top of my beam pile had begun to warp or twist. I’m assuming this was because they didn’t have much weight pressing down on them compared to the beams at the bottom of the pile.

As such, my first two or three available beams were all of the five inch variety, so I had to load them up and carry then back to the sawmill to cut down to three inches. I was surprised to find that they were still as heavy as ever – I suppose it does take some time for beams to fully dry out.


Once I had beams of the right size, I began by ripping the four inch height beams for two sides of the sauna in half vertically. This would allow me to stagger my runs from one wall to the next. I am planning on using the simple, yet strong, mortis and tenon type of joint.


I centred these two beams on opposing walls, making them flush to the outside bricks. I had placed four pieces of rebar close to the corners of the sauna, and heavily mortared them in place. They were only a foot long, and in hindsight I would consider two foot long ones, as one of them did become a little loose from my fitting and adjusting the sill beams.

In any case, I drilled out a hole to allow the beam to settle on the 5 or 6″ of rebar sticking up. I then lined up full size beams on the remaining two walls, and, using a pencil, marked off where I would have to remove material to allow them to interlock.


Flipping the beams over, I used my portable circular saw to cut four 1 1/8″ deep slices through the marked area. One on either pencil mark, and then two more at 1″ intervals. Then, with a 1″ chisel, I cleaned out this cut. With the half beams on the blocks, I did the same thing, only on the side facing up.

Once I had them assembled and looking good, I disassembled them again, in preparation for the next step.


I am planning on inserting two splines on the top of each beam as they go up. These splines should fit into grooves that I plan on cutting into the bottom of the next beam. Between these splines I plan on putting some sill insulation cut into 1″ strips. I’m hoping this will create a really good seal between courses.

My first attempt to cut a groove to accept my 5mm plywood spline was with the chain saw and a chalk line. This was noisy, wavy, and difficult to keep the depth consistent. It did give me a good, wide groove for the spline. But it wasn’t a nice prospect to think of doing this four times two each beam.

I next tried my router with a 1/4″ bit. This was much more physical! The router groaned under the effort, not to mention it didn’t run from my modified sine wave inverter, and I had to run the generator to get it to go.

Finally I tried my circular saw. It actually cut a groove that was acceptable, although just a bit too narrow. I really had to hammer to get the spline to fit.

I am thinking about the possibility of fitting two blades on the circular saw at the same time. We will see if that is realistic.

With the grooves cut into the tops of the beams, I was ready to put down flashing. I wanted to add flashing that overhung the concrete blocks both inside and out, to ensure that creepy crawlies wouldn’t have an easy path up to my log walls. I had found a large roll of it at the dump last year, and only needed to supplement it with about 5′ of newly purchased material at the last minute.


With Donna’s help, I laid it all out and drilled a hole for the rebar.


The hole needed to be enlarged with my snips.


Then I laid down a bead of caulking on top of the blocks, set down the flashing, and finally set down my first run of beams. Exciting!


Crouching down, I could see that the beams didn’t do a great job of compressing either themselves, or the flashing, against the blocks. I tried stacking a few extra concrete blocks on top of the beams to really create a good seal, but alas, wood does as wood does. I will certainly end up going around the wall again with my caulking gun, sealing under the flashing inside and out, and then doing the same between the first run of beams and the flashing.

All in all, it was an exciting and successful start – next step on the sauna will be to actually lay a second row of beams on top of the first one – made more challenging with this spline fitting notion.



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