Planning
Off and on I had considered building a sauna. Not only are they all the rage with fitness influencers - but they are also touted as a boost to heat training and general fitness. Whatever you do don’t make the mistake of clicking on a sauna in Facebook or Instagram Ad - you will be inundated over and over with all the various sauna options from wood burning sauna tents, to barrel saunas to custom 120K sauna builds. (After you build a sauna then you get all the ads for all the extra accessories you need for your sauna : sauna hats, towels, matts, organic cotton shorts etc). Seth had also been of late telling me about his enjoyment of the sauna. So after a considered cabin building venture up near Cle Elum proved undesirable - I decided to settle with building a sauna.
It is difficult to wade through all the sauna options out there - as I researched things watching reviews on Youtube and reading the opinions - eventually I landed on https://www.reddit.com/r/sauna/ and you will find a LOT of opinions - especially the touted superiority of the “true Finnish sauna” - with its heated rocks and the löyly (humidity/steam) - the importance of the bench height and airflow to achieve the perfect sauna experience. The pro-Finnish group quickly point out that barrel saunas are no good - (bad air flow) - that an infrared sauna is not a “real sauna” because it lacks löyly. (FWIW there are 4 million people in Finland and 3 million saunas, so they have a fair bit of experience with them).
So I planned to build a custom sauna as one of my retirement projects. Ironically, prior to building and finishing the sauna - I had never actually been in a sauna. Seems like I really should have tested them out beforehand - but more on that later.
In Dec of 2025 I bought “The Art of Sauna Building: The Complete Sauna Building Book: How to Plan, Build and use an Authentic Traditional Sauna” and read it cover to cover, taking notes and making highlights. (I bought mine from Touch of Finland, not the $480 used paperback price on Amazon). In January I started an extensive Google doc researching and planning my sauna build. I started watching copious amounts of Youtube videos on various sauna how-tos, watching sauna builds and reading Reddit threads. In particular I watched a lot of The Sauna Heater channel. Originally I looked into buying a sauna kit that could be put together - but after reading a bunch of reviews about delays in delivery - I decided to build one “myself”.
What that meant was getting commitment and time from my general contractor buddy : Steve Chapman and starting the process. I was to be the financier - pay for all the materials, be the hired man to do the manual labor tasks (carry the wood down to the site, stain the boards, hold this plywood sheet while it gets cut etc), and be the sauna guy for details where sauna construction guidelines differ from normal construction.
The plan was to build the sauna on an existing cement pad where previously there had been a hot tub. I had soured on hot tubs because they really aren’t enjoyable in the summer and the chemical up keep and constant energy drain to keep them hot is annoying. Since the sauna was less than 200 square feet there was no permit process to wrangle with.
Steve and I met on April 14th to plan the sauna build and go over some of the basics, like the size and general design. We started the sauna build on May 4th - and we completed the last final details on July 16th. We were gone several times during that time period - and Steve only worked one day without me - otherwise we did all the work together. That doesn’t mean that I did an equal share - but I was there.
After determining my desired sauna size - I needed to pick the right kind of heater. I wanted a heater that was electric - and had stones “in the heater” - that would hold and generate heat and when you threw water on them would generate steam or löyly. The two ones that I saw continually were Harvia and HUUM. I decided on a Harvia Spirit SP80E - an 8 kilo watt heater with 110 lbs of stone. There is an annoying trend in heaters (same situation for my outdoor heaters on my deck) where adding wifi - is a very expensive add on - instead of being just an included feature. I wanted a wifi / phone app controlled sauna heater - so I could turn it on remotely. This ended up costing an extra $1500!!!! Ridiculous - but in the end I felt necessary.
Building
First thing we did was build a floor with 2 X 4s and plywood - we set it up on concrete blocks on each corner on top of an existing cement pad. Then put up the four walls and the frame and then the rafters for the roof. Then we put the roof on - and then tar papers and shingles. What struck me is how many different types of nail guns Steve had - I think on this project he used at least 5 or 6 - different gun for roofing nails (circular rolls) - different gun for the studs, different gun for finishing nails and then different nail guns for various sizes of staples. After the roof - we went to Issaquah Lumber and bought a 120 linear feet of 1 X 8 Tight Knot Western Red Cedar Siding - that was rough cut on the outside. The cedar lumber companies won’t sell you boards or even let you pick out boards because then people would pick out all the long boards, or have you cut just 7 feet and leave them with a 4 foot board. And eventually they could have 500 linear feet of cedar that was all 3 foot in length. So really what they give you is random sampling of boards to get to the 120 feet - some shorter, some medium and a bunch “full size”.
The stain for cedar - was funny enough “shingle oil” made by Chevron. Back in the day - they used to stain outside cedar with used automobile oil. Steve had a bucket of Shingle Oil from about 10 years ago and there was still plenty left. Apparently you can still buy a 5 gallon bucket of it online - the description says its a : “straw colored, low viscosity oil designed for use as a shingle or shake dressing for shake roofs, wooden fencing, wood siding, and log homes.” Who knew? Steve was Tom Sawyer and I was the neighborhood kids - my job was to stain the boards. I put them on a set of saw horses and stained them - then laid them out to dry under the deck and then Steve tacked them up to the walls of the shed with one of his many nail guns.
The next task was to wire the interior. Due to the intense heat of a sauna - you can’t use regular wire and electrical materials, you have to buy high temperature wire. We needed high temp silicone wire to go from the 220 wire coming in from outside the sauna to the heater, high temp wires to hook up to the LED lights, and I guess the LED lights need DC Low Voltage Transformer that sat outside the sauna. Lastly we needed to run high temp wire for the lights and switch outside the sauna to turn on the LED lights inside and the outside lights.
After getting that done - comes the “scary” part of drilling holes into the side of the sauna for ventilation. The correct airflow is important for the Finnish wet sauna and the flow of the löyly. We put 4 holes in the sauna. Two small 3 inch vents - on the “left hand” side of the sauna if your facing it - one right below the heater and above the heater. Then on the right hand side - one 3 inch vent underneath the bench - this was hooked up to a AC Infinity fan - that would suck air from outside to promote air flow. And one more vent on the right up high in the back corner - this was a 4 inch vent - which is closed during a sauna session and then opened up at session close to promote venting hot air and drying out the sauna. And of course we then had to install the pipe in the wall for the AC Infinity exhaust fan to push air out the back of the sauna.
From there we applied a bit of insulation around the switch boxes - normally if you lived in a cold place like Finland you would insulate the entire sauna but because of the milder PNW climate we did not. Then we put a tin foil vapor barrier over all the internal studs and securing furring strips on top of each stud. This gives the sauna a moisture barrier. Then back to Issaquah Lumber - this time to 901 linear feet of 1 x 4 Clear Mixed Grain Western Red Cedar that had tongue and groove to use for walls and ceiling paneling. We also had to buy super expensive stainless steel nails that were rust resistant to use on installing the tongue and groove. (Which of course had their own special type of nail gun). The floor stayed as a sheet of plywood. Only ⅓ of the floor is “visible” as you step into the sauna, the area in front of the lower bench - and Steve built a lattice removable floor to cover that area.
Of course “we” had to stain the tongue and groove cedar - a task that I took up - a guy at Issaquah Lumber gave us the tip that GasOne Liquid Paraffin Lamp Oil - was the exact same oil as the expensive Sauna Shield oil. Sauna Shield claims there oil is more refined and AI seemed to assert I was going to catch on fire and blow up - but we used the Paraffin Lamp Oil and have had nothing bad happen - no smells or fires ;) That was a lot of boards to stain and then let them dry a bit - and then Steve would nail them in place. Now we had a mostly finished cedar box - no benches and no door. Those were next.
The sauna has two benches that go in an L shape around 2 sides of the sauna while the heater sits in the corner. There is a lower bench for your feet and an upper bench that you sit on. This upper bench puts your head about 10-12 inches from the ceiling - depending on the size of your torso - that is where the löyly rises to and flows across the ceiling and then down and out through the exhaust. This is why you want a sauna with a flat ceiling and not one that is too high. Back to Issaquah Lumber for more cedar for the benches and the door : some 1 x 4 boards for the benches, a couple of 1 x 8 boards for the door and some 1 X 6’s for the bench frames. The bench surfaces have ¼ inch gaps between the boards and are nice and secure when sitting.
Steve took a bunch of cedar home to make a door and I ordered a piece of tempered heat resistant glass for a window in the door. The door has a wooden handle inside - so as to not burn your hand on hot metal, the door doesn’t use a traditional door latch that requires you to turn a handle, but is instead a ball catch latch that allows you to open the door with just a push. (Mostly as a safety factor if you need to get out quickly).
In mid-July and the electrician came to do the wiring and Steve was there to hang the door, get the heater installed and other sundry tasks, like building me a little shelf to put my phone on. The wiring for the sauna is a complex process - at least it looks complex to a novice like me - _AND_ seemed in actuality to be based on how long it took a seasoned electrician to figure it out (though it was his first time wiring up a sauna). There was a bunch of details about breakers and volts and jumpers and two vs. one - but after about an hour of troubleshooting, reading the diagrams and checking the circuit completion with an electrical multimeter we got the heater firing off and on. We turned the heater on and then let it “cook and sit/air” for 24 hours.
The next day Steve installed the LED lights, hooked up switches and lights and put the door on and we did an initial sauna session together. It was nice to have a custom built working sauna! Would I have learned more if I did it all myself? Absolutely! Do I feel like I learned real construction skills? Not really. Do I wish I would’ve done it all on my own? No, I realize it would’ve been a much slower process and had a lot more anxiety with many mistakes made. (And I didn’t have 6 different nail guns, 2 differetn saws or 4 different kinds of screw guns and innumerable tape measures - like Steve did). But I am very lucky that I had a choice, and I could hire someone to help me build it and I’m glad I did get to see the process and be involved.
Using the Sauna
Since then I have been using the sauna 4-5 times a week, with sessions ranging from 155 to 194 degrees (the max temp). I have been really loving the sauna and here are some of my observations.
You do build up a tolerance for the heat over time. At first 165 felt intolerably hot but now feels mild. I will do short sessions like 15 minutes and the longest at 30 minutes and I vary the temperature.
Generating steam (löyly) when it washes over you makes it feel at least 30 degrees hotter and can take your breath away and make it hard to breathe. Sometimes I’ll do the entire session “dry” with no löyly and other times I’ll do 15 minutes dry and 15 minutes with steam. And sometimes löyly the entire time.
A sauna session builds over time in how it effects you - meaning as your core body temperature rises your heart rate will increase and you will “feel the heat” more at the end even though the temperature may not have materially changed. Sometimes hanging on for those last 5 minutes can seem unbearable.
What you wear in a sauna is “different” than what I thought. Don’t take in your glasses or your watch; don’t wear synthetic outerwear but instead wear all natural materials like cotton shorts. Basically the high heat will ruin most normal things built for normal temps. Which means no phone - so I have a high heat tolerant bluetooth speaker and I play podcasts or audio books from my phone outside the sauna. Wearing one of those wool sauna hats does really help you not feel the heat (obviously on your head). And I usuallyl wear a heat resistant heart rate monitor and record a “Yoga” session on my phone on Strava so I can see how my heart rate changes over the session.
The temperature that you read on the thermometer is not the consistent temperature throughout the sauna. There are two probes that came with my Harvia heater - one that sits directly above the heater and then one in the far corner near the big drying vent. The temperature that the heater reads comes from the probe above the heater. So if you set the sauna temp at 194 - that is what it will read directly above the heater. (I used a Infrared Thermometer Digital Temperature Gun). The heater is full of stones - and those stones will be up to 220 degrees - holding and radiating heat. When the gauge trips below the target temp - the electrical heater coils in the heater will fire and heat up the rocks and the interior of the sauna again. Even at 194 degrees measured above the heater - the corner of the bench where I set might be only 160 degrees and if I measure down at the exhaust vent below the bench it can be only 70 degrees. But when its 194 and you reach your hands over your head (or feet if your stretching) you can feel the extra hot hot heat on your digits - it is hot!
I have also made a sauna pre and post session list of instructions for Miles or others that want to give it a try.
Cost Breakdown
Maybe this is the part that will interest some folks, I dunno for sure but I am including it. You can see the full list of everything that we bought, I kept track pretty religiously along the way. With sauna accessories my total cost was $28,134, which breaks down as :
It is pretty typical that labor is going to be about 50% of the build cost and when your getting premium materials and custom build - it takes longer and costs more.
There are 100% cheaper saunas that you can buy (or build); they are not generally going to be made with cedar but typically made from heat treated spruce or pine. And the price you see on the website is never the all in cost. For example as of this writing you can buy a Redwood Outdoors 3 Person Cove Outdoor Sauna for $6700 - which comes with a heater and is built with heat treated Spruce/Pine; to get one with Western Red Cedar will run about $9000. You’re going to spend an additional $3700 to $9700 for the rest of the stuff : any wifi controller upgrades, freight delivery fees, base pad installation, 240V electrician hookup, un-crating and assembly and good old sales taxes. So the $6700 will cost you all in will cost you between $10,300 – $16,400.