Wood Burning Sauna DIY

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Introduction: Wood Burning Sauna DIY

This is my first Instructable but I have used so many for ideas and love the community input!

I live in downstate Michigan and went to college in the UP met a whole crew of Finlanders and was introduced to the Sauna! and its pronounced SOuna not SAWNA but i still slip from time to time if you arnt a yooper it takes time.

I graduated and moved back downstate for work but my life was lacking because i no longer had access to the "poor mans medicine box" so naturally i want to fill that gap. Research began to see my options for having my own sauna. Student Loan debt is a mother sucker and takes up a large portion of my income so $$ was tight so building looked better than buying and of course is much more rewarding.

I searched the web and found a few things but nothing really helpful for building a finish style  wood burning sauna. I am getting into woodworking its becoming  my after work hobby and this was the largest project i have done and still have a few things ill get to at some point. So I winged it at times but at the end of the day the sucker works as intended.


Step 1: Fall 2013 Update

The Sauna has been up and running for over a year now and been used about ~70 times. It has grayed from original yellow looking pine on the exterior and the cedar interior is still aromatic but less intense after time has gone on. The window that cracked has been replaced by an vinyl window picked up from Habitat for Humanity for $20 and a woodbox/bench has been built. Over the summer it didn't get used weekly but now that fall is here it is Sauna season!! I also improved the rock to stove pipe ratio by taking a section of steel wire rack and bending it to create a cylinder. The heat has been able to be held for a much longer time with these additions and looks pretty good with the flowers in bloom.

Step 2: The Stove

I wanted to do this DIY and on the cheap and after seeing a few stoves made from propane tanks I checked the garage and we had a 20lb tank collecting dust. The tank had been used but was empty so I Took off the fitting with a little elbow grease and let it air out for an hour. I then filled it up with water and let it sit for 20 min. Then it got tossed in the fire pit and burned for an hour to remove any traces of propane and the nasty additive that I believe is poisonous. 


I wanted to keep the building small and fit 3-5 people so to save space I made the choice/mistake to have the tank sit upward. I went to the hardware store and purchased 8ft of 6" single wall stove pipe. Which i cut a hole  smaller than the pipe in the tank using an angle grinder. Lots of sparks and loud but pretty fast work. 


I made a door in the front and used steel banding and sheet metal screws to attach the strapping and door hinges. Because the tank was vertical not horizontal i had to create a baffle to keep the fire in the fire box and not in the stove pipe!  So i used a piece of plate steel and some bolts so i could adjust the air gap to the optimize draw but still keep the fire in the box.

Note: in the picture u will  see a piece of air duct on the tank this is galvanized and a big NO NO for a chimney end up with zinc poisoning but it is 6" and worked for a demo fit. I made a cage for the rocks using steel shelving.

I put on a section or 2 i believe of stove pipe and balanced it while i tested the baffle until i was happy. I was getting results i wanted and was ready to start building the frame for my sauna shed.

Step 3: The Game Plan

Step 1 was complete I had a fire box that seemed to be working pretty good and i was able to do it weld free. I knew the project was going to cost a few hundred bucks but was going to be frugal and resourceful as I could without sacrificing to much time to save a buck. So I looked at what floor plans i could find on the web and for dimensional lumber reason I decided on 4'x8' and settled on a shed roof that would be 7ft on the high end and 6ft 4 on the short end.

I really wanted to have this be a legit sauna and cedar was the wood of choice. But no way jose would I be buying that much cedar at a big box store thats the opposite of a frugal build! 

So i searched hi and low to find cedar. We have several Amish saw mills around here but no cedar mostly hardwood that fuels the pallet industry but very cheap rough cut wood if you live in the country and you have access to a planner good way to go.

But I found a place with a resaw bandsaw that had 5x5x8ft western red cedar blocks that ran $18 per and could get them re sawn to any thickness

I also found a local guy with a tractor powered sawmill who had white pine for cheep.

So the plan was formed. I would build a frame using dimensional lumber and line it with ~3/8' cedar boards and then the exterior would be .75-1.25"  white pine. I could insulate and install a vapor barrier with 2 layers of wood sounded doable and heat worthy

To save $ I cut 2x4's in half and the frame was built one wall at a time. The pine boards were 9-15" wide and 8-11 ft long and varied from .75-1.25 thick. I ripped each board in half and was left a variety from 4.5 to 7.5" wide.

I used a ship lap of about 1/2 inch on each board to create a more air tight seal because the boards are gonna move around with the moisture and the changing of temps. I didnt use any pressure treated wood in this project for health concerns so it may only last 5-10 years but by then ill be ready to build another one! The wood will age and enhance the rustic look.....

I had the four walls mostly built but was ready to see the space i had created so using the tractor and a trailer moved the walls into place and got some screws in and i was happy to see the 4 walls were square enough and standing strong.

Step 4: Button It Up

I continued to nail up pine boards until the exterior was up to the roof level, which is at an angle so the boards near the top had to be cut at an angle to follow the roof pitch. My dad gave me a hand and we framed out the roof and purchased some steel roofing in a lovely forest green. 

The door was made from left over pine boards that already had the ship lap cut in them and a ~100 year old window I found in the attic that imagine was from when my parents house was built. I wanted to do a curve door but should of just stayed square would of been easier...

I attached a spring to the door and wall to keep it closed and that heat in!

The window was made from a plate of glass that I had laying around. 

I had a whole mess of plastic sheeting from past projects and using a stapler I created a vapor/wind barrier on the inside of the frame. I came across 3 sheets of polystyrene foam insulation board and cut it to fit between the studs on all the walls and the roof expect in the area where the stove pipe will be.

I then had my cedar hookup cut me up enough boards to line the inside with the western red cedar. Each board was 5.25 inches wide and had to to be touched up with the table to be square enough for my liking.  I chose not to ship lap these boards and just lay them on top of each other and use an air nailer to make this step a little faster.

I did a wall at a time and it did go quick. I then was ready to cut a hole in the roof for my stove pipe. I measure to where the pipe would need to be and then using a jig saw and a fresh blade i cut the opening and put some pipe in and set the stove in place.

Its not a perfect fit and when it rains water drips through but its minimal. 

I had some cement board around and used that as a barrier from the wood stove and the walls its not the prettiest but so far has done its job.

I wanted two rows of seating at different levels so I ended up going with a bleacher style set up and used  left over cedar and oak for that it fits 4 people full house and very comfy with 2.  Not the best pics on the inside the lighting makes it hard to show.

Under the bench is open and i currently store fire wood and the water bucket there but i may add some boards to close it in.

Step 5: Stove Redo

Well it was looking like a sauna and technically did work but It would take 2-3 hours to reach temps of 150 degrees. And never really was hot enough for my liking. The stove had great draft but i think a large portion of heat was lost out of the top of the stove pipe based on the vertical design. So I searched craigslist and found a larger 30lb tank for $10.

This time i wasn't messing around I wanted to keep more heat in the building and opted for the horizontal design which appears more commonly done with the propane tank wood stoves. It was a good move, and basically repeated the same process and built some legs and  a larger door than before and cut up the old stove to use as a baffle for the new one. which fit like a glove because it follows the curve of the tank.

I also used a section of the old tank where the door was cut and turned that into my rock holding tray. Which my brother grabbed a load of rocks from a quarry and so far non have exploded...

Now the sauna heats up rather quickly in about 45-1hr its ready to use.

Step 6: 4 Months In...

Sauna has been up and running for 4 months now and gets used about twice a week. It burns about half a wheelbarrow of wood each fire so that has been my biggest challenge is finding dry fire wood. Having the right wood is key so much easier to get the hot box up to temp if you have a dry supply.  This summer I will stock pile up but so far burning pallets and scraps from the sawmill. I avoid burning plywood or pressure treated but oak pallets burn hot.

The wind also plays a big role in the draft and a slight breeze seems to be best for the quickest hottest fires. I had a whole bunch of  oak and pine strips and on a 18 degree day had the sauna at 201 degrees which is as hot as i go, usually 175 is my zone.


We got some wet snow and eventually rain but u can see the snow difference on the roof from before and after a fire.

I use a kitchen thermometer to gauge temp and that hangs 6" off the ceiling on the high side of the sauna hit 175 today.

 


Step 7: Review

If you live in the country and dont have major zoning/building code issues to overcome this is a totally doable project. It is a little messy and ash tends to get on the floor. 

Stove design is key and the next sauna i build i may just find a used woodstove and save the headache. 

Cedar is nice but i might just go all white pine it smells so good and is cheep and really haven't had issues with sap.

The window was kinda of bust it basically is a huge heat loss and didnt last long the plate glass cracked and for now is covered up with plywood, ill be keeping my eyes open for a small window.

I used alot of scraps from other projects to build this and spent about $325 in supplies. U might be able to spend less but not with out sacrificing time time time. 



Feel free to leave your comment and ask questions. I am the type of person who learns best from doing things on my own, They may need to be improved but thats learning. My dad is a mechanic and my brother is an engineer so I am constantly told how i could of done things differently, yah well i didn't so to bad!

Thanks Enjoy!!!!!

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117 Discussions

Hi, just a note on the window. Find a window repair co. and ask about getting a piece of tempered glass( it will be more expensive, but won't crack as it is fired to give it a harder glass). They may have a piece sitting around that they may sell for cheaper.

0
user
PemaC1

1 year ago

Does anyone know of a carbon monoxide monitor that is suitable for a sauna? Most of them can't be used in a heated or humid environment. I can't find anything online and wondered what others have used?

8 replies

No, but if you nee a CO detector, then your Sauna isn't safe to begin with ... with your concerns, I would opt for the infrared (electric) heated unit.

This comment is smug and unhelpful. Instead of telling everyone how sauna smart and experienced you are, why not just explain why you feel a carbon monoxide monitor is unnecessary for a sauna. It is a rational concern: small rooms with wood stoves can be dangerous (we've all experienced down drafts filling houses and cabins with smoke)

Speaking as someone of finnish descent and who grew up using a sauna almost daily, a properly built sauna will have the feed for the stove on the exterior of the sauna, which means a CO detector shouldn't be necessary. I would never recommend going in a sauna which feeds the stove inside the sauna room.

outside-wood-burning-heater.jpg

I'm from Finland and vast majority of wood sauna stoves are fed from inside! We have two million saunas in Finland and I've never heard any case of carbon monoxide poisoning, but it is always a possibility when using wood. Perhaps cold and dry weather we have here keeps draft good enough. Traditionally stoves don't have damper plates on them, only boilers. Lack of damper plates is because it allows sauna to dry after use.

Oldest saunas(Savusauna = Smoke sauna) don't have chimneys at all just small holes in wall and you'll first carry benches out and heat ton of stones. After all wood is burned you carry benches in and enjoy sauna for hours.

As for statistic in whole of Finland there was 10 carbon monoxide poisoning deaths (probably most from closing damper plates too early this number includes all cases not just sauna related). Other deaths in sauna was 45 so slippery floor or too much to drink in sauna (if you fall asleep in there it is dangerous) is much more deadly.

https://www.stat.fi/til/ksyyt/2010/ksyyt_2010_2011-12-16_tau_004_fi.html

I've used wood saunas in Finland where they were internal. never heard of a problem. I suppose as Finns use them like crazy as a nation there must be some level of annual incidents ?

What he is saying is if you have doubts about CO you would not use such a sauna. you wouldn't take the risk, hence never having a CO monitor. All the Finnish saunas I have been in, are very well ventilated, and the process of dousing the first Loyll of water (excuse spelling) eliminates any remaining embers.

hi Pema I'm looking around for the same thing. Let me know if you find anything. I was planning to use a household CO monitor and seeing what happens. I'm almost done with my sauna and have fired up my stove once. I used a multirae gas meter from work and the highest the CO got with stove doors closed was around 8 ppm which I hear is not so good to be sitting in for a prolonged period. Thanks

Hey man! Just wanted to tell you that I was inspired by your instructable over a year ago, and embarked on my own project. I started with a plan to follow your lead, recycled pallets, diy heater, etc. I sold my wife on the low cost, but we ended up going way overboard and changed the entire scope of the project. Not as “affordable” we we initially intended, but I just wanted I say thanks for the inspiration. Here’s the instructable I posted about the build:

https://www.instructables.com/id/Finnish-Sauna-1/

Ok Finn's other experienced people, do you need the vapour barrier? i was planning lumber of some sort outside, cedar or pine inside? seems to me the sauna will be steamy, but for couple hours after the sauna is done it'll still be hot, also would the vapour barrier not actually hinder a drying out process? Lastly if not using vapour barrier is rock wool sufficient insulation, or something else?? thanks m

Looks good! A suggestion for you for a cheap but heat proof window. An old oven door window can be picked up for next to nothing and should be a lot more stable for you. You'll of course need to frame it yourself but that's half the fun.

1 reply

very inspiring. I am retiring soon, I hope to build a sauna next to my cabin (after I build the cabin, lol). You (and your commenters) have brought up several good points to consider for the project.

Thank you.

Awesome Project!

Can I ask where you sourced your Cedar from? I live in NW Ohio and I may be able to use same source.

Thanks, Dustin

RE: Exploding rocks. This is a big risk but a little basic geology knowledge will help you out. We have built a lot of native-American style sweatlodges using hot rocks for heating, just like a sauna except made out of tarps and blankets. Chert, which is commonly found associated with limestone, will explode when heated. Shoots hot splinters all over the place, one time right through one of my tents. Many other kinds of rocks will not, (this is based on experience) including granite (might be common in Michigan?) limestone without chert nodules, sandstone. Most igneous rock (basalt, granite, etc) should be OK. I'd probably stay away from Shale, Coal (this could burn!), and anything crumbly (might hold water which could explode).

Keep this in mind: Some rocks are Gneiss-er than others, but you can take it for Granite that these should be fine. Your sauna will be hot, not Coal, if you follow these instructions. If you can't keep this list straight, put it into a checklist on a clipboard and keep it as a Chert on the wall. Never Basalt your food before tasting it. Now the judge has finally banged the Gravel.

2 replies

Be careful with the sandstone. I had a piece of flagstone explode violently and crack a cast iron wood stove. The stone was sitting on top for about an hour before exploding. We were lucky no one was hurt. The stone hit the fence behind us with some serious force and had all the dogs in the neighborhood barking.