Building an Outdoor Sauna Using a Wood-Fired Sauna Stove

by Mike Mutzel


The coronavirus pandemic has thrown a monkey wrench into many of our favorite routines—from travel to exercise and even sauna bathing. Health authorities closed down public saunas saying they’re high-risk (even though their high heat is known to kill off pathogens). Go figure.


At least we had our at-home, High Tech Health infrared sauna to fall back on. This Colorado-based company makes one of the best at-home infrared sauna units.


There is only one small wrinkle: over seven years, my body has become used to the 180 degree F temperatures offered in the sauna at my gym. (The infrared at home helped fill in the gaps.)


In August, when gyms opened up again in the state of Washington, the sauna remained closed due to safety. So I was determined to build my own—from scratch.


I’d already mentally mapped out the spot in our yard where the outdoor sauna was going to be built, and I had been casually clearing the landscape in that part of the yard thinking I’d get to it next summer.


This was a sign from the universe that the sauna had to be built, even though I wasn’t ready. (Isn’t that how things always work?)


I searched for websites and blogs about sauna therapy and came across Glenn Auerbach, the site’s owner and the author of an e-book I’d bought to help me along the way, built his first sauna over 35 years ago and now has three wood-fired saunas! (He’s also helped many clueless people like me to build their own.)


Related: How to Get Started with Back Yard Sauna Therapy

Glenn’s website has been invaluable. Over the last 90 days, I’ve visited it at least once a day to get answers to my questions. I’ve also come across custom sauna builder Rob Licht’s site as well—and purchased his e-book. (I’ve used bits and pieces of their books throughout this project.)


Glenn’s e-book sold me on the idea that the basic structure should be 8 feet by 12 feet with a wall separating each 6-by-8 room. You walk into the changing room (AKA cool-down room) where you can access the hot room.


I staked out the area, including the 5-foot setbacks required by my city’s building code, and called a concrete truck to deliver a yard of concrete. I was lucky they had an opening the next day, which meant I had a lot of work to do (as in digging six 12-inch holes that were 4 feet deep with rebar to support them).


Working under pressure is a great way to get things done, but most importantly there was a stretch of good weather that next week which allowed me to get the majority of the framing done while my stepdad (a contractor) was visiting.


Off to Dunn Lumber I went to buy six 12-inch sonotubes (that would be used to house the concrete to hold the base of the structure together.) I worked so hard at digging that morning that my arms were literally cramping by the time the concrete truck drove up. (I was so nervous hearing him pull up as I wasn’t ready, but I made it work and the six 12-inch supports were more than enough for this structure.)


After hand shoveling a yard of concrete to the back, all the tubes were filled. I inserted Lord knows how many rebar into the fresh concrete and used a string to drop in the brackets for the 4 by 6 ledger that would make the base support.


Thankfully everything was reasonably straight and plumb. That next Monday, my stepdad and I went to Dunn Lumber, got the framing we needed to create the floor joists and subfloor and went to work. (The floor joists are fun as you use hammers and nails like the good ole days.)


Once the subfloor was ready, we added the framing, top plate, roof joists and the ridge. I probably could have done most of it solo, but it would have taken twice as long. Having my stepdad around to review framing and teach me how to make a ridge and roof rafters—something I’ve never done before—was very helpful. Plus we had a blast outside listening to music and hammering for the last sunny days of fall.


With the framing in, next came the plywood sheathing around the exterior and roof followed by installing the felt paper to the roof and Tyvek on the exterior sides. I hustled to get this part done so the structure was water tight, as fall was upon me.


I spent $120 on shingles, borrowed my neighbor’s nail gun and put up the asphalt roof over a weekend in early November. I was about $4,000 into the project at this point, and as much as I wanted to keep things going fast, I needed to slow the burn rate to hit the pause button on the build. Plus the holidays were coming, and we had travel plans. (We went to Hawaii to celebrate my dad being 70 years young.)


In early December, I sold our infrared sauna to get the cash to buy the wood stove. I promised the folks who bought our sauna that I’d assemble it for them and deliver, so that zapped a workable weekend, but it was worth it. The Lamppa Kuuma was roughly $1,800 plus $350 freight to get the 500-pound iron stove shipped from Minnesota. Lamppa Manufacturing makes an amazing wood-fired sauna stove.


With the stove on order, it was time to add a deck and front door and finish up the exterior siding. This was about $2,000 for the materials and took me a weekend plus a few weeknights to complete. I made a K-frame door out of 1-by-6 cedar and used an Elk shed from a hunting trip in Idaho for the door. It has added a great touch.


In mid-January, the stove company told me the unit was to ship soon, so I had to get the interior done—quick! This meant adding two 10-by-14-inch vents just below the peak of each ridge on the 6-foot sides of the building (you don’t want mold!). It also meant adding two additional floor joists under where the 500-pound stove would sit. (Note: double up on floor joists in the whole hot room so you can pour a concrete floor instead of using Durock cement board—it will be faster.)


I used mineral wool insulation. Sadly, I didn’t wear a mask at first—my lungs are still pissed at me! I added blocking where the top and lower benches would be. Then I wrapped the hot room in aluminum foil from Cedarbrook Sauna. This is where Glenn and I disagree: He suggests this aluminum foil bubble wrap that has plastic in it and is available at most big box stores. (Your health, plastic and heat aren’t a good combination, so I opted for some stuff that’s harder to work with but safer over the long haul, IMO.)


Insulation and foil barrier meant it was time to get the stove ready for delivery. I laid some cement board on the corner where the stove would go, added some landscape pavers to support the stove from below and used an 80–pound bag of type S mortar (in cement speak, “S” means strong, which means it has Portland cement added that is also waterproof.


I let this set for two days and sprayed it with water to help it harden (keeping concrete/mortar wet for the first few days leads to a stronger product, I’ve read). I then rented a hand cart and somehow got the 500-pound stove from my driveway, up two decks and into the sauna. (Thank goodness for deadlifts!)


With the stove in place, it started to feel real. Next up was buying the chimney and cutting the hole in my pretty roof (always scary) to help the stove draft. I didn’t feel comfortable with it, but after a long chat with the great folks at Thompson’s Hearth & Home, where I purchased the chimney, I felt competent enough.


I used the cardboard from a large box from one of our MYOXCIENCE vendors to match the ellipse-shaped hole that needed to be cut by tracing the flashing that houses the top of the chimney pipe onto the cardboard. (There’s a more mathematically accurate way to do this, but my shortcut worked just fine.)


I took the big piece of cardboard, hung a wrench tied to a string from the interior of the ceiling and found out exactly where the middle of the ellipse should go. I made my mark and used the Milwaukee sawzall to make the cut (as assault chunks fell onto my face).


With the chimney in, the moment of truth was upon me: a small test fire to see if it drafts. It did! I could hear the hot combusted air being sucked up into the chimney vent. Excitedly, I ran outside to see smoke. My wife and daughter were excited too but didn’t really understand the significance. It was just another fire—what’s the big fuss. (They didn’t lose sleep over cutting a hole into the roof either, so I get it.)


Since the stove has been installed and functional, I’ve been working with small test fires as I build the floor—the stage I’m at now.


All that’s left is sealing up the cement board with a layer of mortar, gluing the 2-inch PVC pipe that will drain sweat from the wood-fired stove and adding 1-by-4-inch cedar to the sides. That part’s easy!


It’s been a fun project. If you have just a tiny amount of building experience—I did a few projects with my stepdad in college, and we built a deck and shed together a few summers ago—you can do it, too.


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