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Turn That Shed Into a Sauna: Step-by-Step Tips

Out of personal experience, Chris writes practical and helpful articles about how to make items and accomplish tasks.

This article describes how to turn an existing shed or outbuilding into a sauna. The following information is covered:

  • Vapor barrier
  • Insulation
  • Interior wall boards
  • Ventilation
  • Woodstove

The Finished Sauna: A Job Well Done

Job Complete

Job Complete

The Idea

My sons and I had been talking about turning that small shed in the backyard into a sauna for years. Finally, in the fall of 2009, we made our move. We each did some research and then set to work building a sauna of our own. Read on to discover how to turn an old shed or an outbuilding into a sauna.

The entire project cost us about $1,000, but keep in mind, we found a wood-burning stove for no charge.

View of Insulation, Moisture Barrier and Cedar Wall Boards: My son, Scott, did a wonderful job on the sauna.

View of Insulation, Moisture Barrier and Cedar Wall Boards: My son, Scott, did a wonderful job on the sauna.

The Insulation

The first thing we did was to get some insulation for the walls of the shed which we were converting into a sauna. We used rolled, fiberglass insulation for both the walls and ceiling. Insulation is described in terms of its “R” value. R13 is good for the walls of a sauna and R26 for the ceiling. Use the same insulation in the ceiling as for the walls, using two layers running the top layer perpendicular to the previous layer.

The Moisture Barrier

Next came the moisture barrier for the sauna which is made of aluminum foil. These specially made foil barriers can be hard to find and are expensive. We solved the problem. Gordon Food Services sells large rolls of heavy-duty aluminum foil. We built the sauna in 2009. I used the aluminum foil in the kitchen through 2013. The foil used as a moisture barrier for the sauna must be put on with the shiny side facing the interior of the sauna so that it reflects the heat back into the room.

Installing the Ship-Lap Cedar Wall Boards: Nice job, Dan (my younger son).

Installing the Ship-Lap Cedar Wall Boards: Nice job, Dan (my younger son).

The Cedar Wall Boards

Next, we looked for cedar boards for the interior. We could have gone to a lumberyard and gotten tongue and groove boards, but those are expensive. My sons looked around and found a small, local mill that had a stack of unfinished cedar boards sitting outside. We had the boards planed and brought them home. The question now was, how we would connect the boards. Would we tongue and groove them ourselves, overlap them or find another way? As we discussed it, we came up with a design that we later found actually has a name. It is called shiplap, and it is made by cutting the edge of the board into an L shape. On each edge of the board, the L faces the opposite direction. As the boards are put into place, opposite-facing Ls overlap. Our sauna was becoming a reality.

The Shed We Converted Into a Sauna: This photo shows what we wanted to turn into a sauna and why.

The Shed We Converted Into a Sauna: This photo shows what we wanted to turn into a sauna and why.

Preparing the door: Dan working on the door of the sauna.

Preparing the door: Dan working on the door of the sauna.

Aluminum Foil Moisture Barrier

Aluminum Foil Moisture Barrier

We were able to get this excellent used stove for no charge.

We were able to get this excellent used stove for no charge.

The Wood-Burning Stove

The sauna stove was the next part that needed to be done. We covered the wall space near the stove with cement board and in addition we lined the wall closest to the stove with paving bricks stacked on edge. You will need to check local codes for the distance required between the sauna stove and wall. We ran the stovepipe through the wall at stove level and then up the outside of the building. This required a lot of custom work that wouldn’t necessarily be helpful to anyone else. Be sure to get the proper pipe for going through the wall, as it needs to be double walled pipe so that the heat is reduced where the pipe comes into contact with the wall. Also remove any material on or in the wall around where the pipe passes through that is not fireproof. If it is even close, it will catch on fire.

Ship-Lap Cedar Wall Boards

Ship-Lap Cedar Wall Boards

The Floor

If you are planning to convert a shed into a sauna, the floor might take some special attention. The work on the floor ranges from replacing it to doing nothing. What is the condition of the floor before beginning work? Are there gaps between the boards? Is it already a tight fit?

The floor of our shed had half-inch gaps between the floorboards. This was going to allow lots of cool air to enter our sauna, thereby making the lower part cooler than the upper. We chose to use fiberglass strips and resin. The problem has been that the finished floor holds a lot of heat. I suggest laying down well-sanded boards on the old floor and installing a drain. The sauna's heat will dry the wood, preventing any problems associated with moisture.

Another suggestion is to pour a concrete floor and install a drain. Over this, install raised, slatted wood floors. These could even be removable for cleaning purposes.

Enjoying the First Sauna

Enjoying the First Sauna

The Stove and BTUs

Choosing the sauna stove is quite complicated it seems. It depends on the construction of the sauna, window and door space, ventilation, outdoor temperatures, and the construction of the sauna stove itself. The figures for determining the BTUs needed to heat the sauna are as follows: Cubic feet to be heated (Length x width x height = Cubic feet); Temperature change (Maximum desired inside temperature minus the lowest expected outside temperature). Follow the link below, enter the data, and get your BTU information.

BTU Calculator

  • BTU Calculator
    Calculator to estimate the amount of BTU needed for the heating of your space based on the size and temperature change. Also find hundreds of other free online calculators here.

Ventilating the Sauna

We chose to put one vent in the sauna, and we located it near the ceiling on the opposite end of the sauna from the door. At the bottom of the door, we allow outside air to enter the sauna while the warm air escapes through the vent near the ceiling of the sauna.

Simple as That

A sauna is relaxing and fun to use. When you entertain guests at your house, have them bring their swimsuits along so you can all enjoy a sauna together. Good luck on your next Do-it-yourself project, whether it is turning an outbuilding into a sauna or some other cool addition to your home.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Comments

Chris Mills (author) from Traverse City, MI on November 18, 2018:

Helen, Thanks for reading my article about building a sauna. We removed the original window to eliminate the gap between the upper and lower panes. We replaced it with single panes of real glass. I am not sure how plexiglass would hold up to the heat. We also were cautious about having anything inside that might give of fumes when heated. That meant painted window frames and calking. I hope this helps. Good luck.

Helen on November 18, 2018:

Hello, Is there anything special that you need to do with the windows, in order to convert the shed to a sauna?

Chris Mills (author) from Traverse City, MI on July 15, 2018:

Em, thanks for pointing that out. I added it near the beginning. The entire project cost us about $1,000, but don't forget that we found a free wood burning stove.

Em on July 14, 2018:

You forgot to mention how much it cost!! ??

HannaHuma on February 03, 2018:

Wau! Very interesting project with full of creativity. I found your sauna project, when I was seeking new ideas and thoughts for my "project". I have been designing sauna collection for finnish market. If interested, you can check www.newsauna.fi

ToddMichigan on January 09, 2018:

thank you much for this response Chris. I will give your best to the Mitten during this winter!

Chris Mills (author) from Traverse City, MI on January 07, 2018:

Todd, You are in my home state. I’m in Montana working right now, so I am missing another Michigan winter. Our sauna is roughly 8’x6’x7’. There is one bench along the 8’ side. Another is added when needed that sits in front of the stove opposite the long bench. Five is comfortable. Six is pushing the comfort pretty hard. More than that and it is best to divide into two groups. Most of the time it is my sons and me when I am home.

ToddMichigan on January 07, 2018:

What is the size of your shed? Now that you have been using it, has it proven to be of good enough size/sq footage?

thank you!

Chris Mills (author) from Traverse City, MI on December 19, 2017:

You are welcome. Good luck with the sauna.

Tariq Bekavi on December 19, 2017:

Wow, thank you very much.

Chris Mills (author) from Traverse City, MI on December 18, 2017:

Tariq, I have never owned an electric sauna, but I have done some research. Are you saying your sauna is 3 feet by 2 feet? I assume it is about 7 feet high. That is 42 cubic feet. The link you sent shows a 4.5kw stove. You may be buying way too much stove. One or two kw should do it. What I've read is to allow for 1 kw per 45 cubic feet. You may not find less than 2kw though. Electric heats fast and your sauna is small. It will be hot in minutes.

Wood vs electric. Atmosphere is a big part of it. If you are into the whole sauna experience including splitting wood, lighting and tending the fire, then a wood stove would be fine. If you simply want to take your sauna and get on with your evening, I would suggest electric. You will use it more often because of the convenience. Don't get me wrong, I wouldn't trade my wood stove sauna for anything, but my sons and I enjoy the whole experience.

Do some more checking on the kw, but I recommend 1 or 2kw. You seem to want it to heat fast. Go electric. Wood takes a while. I hope this helps.

Tariq Bekavi on December 18, 2017:

Hi, can you help with the choice of electric heater?

My sauna will be 3x2. And I do not know exactly which electric heater will heat the sauna in an hour or less.

At the moment I chose: https://spaprof.com/category/electric-heaters-and-...

Did I choose the right one? Also can you tell me what the pluses of wood burning stove? Thanks for the help.

Chris Mills (author) from Traverse City, MI on September 16, 2017:

Scott, sorry it took me so long to get back to you. We used blue board for insulation, then added the foil moisture barrier, then the cladding. We don't see much warping. The door works fine. I hope that helps and is in time for your project.

Scott on September 13, 2017:

Hi there,this is exactly what I'm looking to do aswell,but I have a question about the door to the sauna, did you just put cladding on the inside of the existing shed door or did you insulate that aswell? Also if it's the original shed door does it not warp with the heat? Thanks and great job by the way

Chris Mills (author) from Traverse City, MI on August 29, 2017:

Heidi, First we cut a drain hole in the floor. Then we used fiberglass strips and resin which come in a kit. You could also try a vinyl concrete floor. It comes in bags to mix in a wheel barrel or in ten-gallon buckets already mixed. begin thicker at the walls and slope toward the drain. Here is a good website for the floor. http://www.saunatimes.com/building-a-sauna/a-great...

Good luck with your sauna. Enjoy.

Heidi on August 28, 2017:

What did you use on the floor to keep it from rotting from water? I'm building one out of a existing shed that has plywood flooring already installed. Thank you

jitendra singh on June 26, 2017:

Very nice

Chris Mills (author) from Traverse City, MI on September 25, 2016:

Faith, Down here you would get a couple months use out of a sauna. It's not enough to justify a large expenditure, but a small outhouse sized sauna would not cost much. My sons did most of the work. I just paid for it.Thanks for stopping.

Faith Reaper on September 24, 2016:

Wow, Chris, this is so cool ...um ...hot! What a great idea to turn a small shed into a sauna. I would love one, but living in the Deep South ...not to practical for outside here, although it does dip down into the low 30s and lower at times.

It's great you and your sons worked on it together too. I love the photos you included here, especially of the snow contrast against the shed. I would certainly have to build myself a sauna if I lived in such cold areas with that much snow!

Great job!

Chris on May 03, 2016:

Outdoorsaunamndiy, congratulations on finishing your project. You are going to love it. Regarding the foil, I think we jumped on the first thing that was cheaper than the alternative. Thanks for reading the article and for your feedback.

outdoorsaunabuildmndiy.blogspot.com on May 03, 2016:

Hi, great build! It's blogs like yours that inspired me to build my own outdoor sauna. I see you used foil-- I went the bubble foil route. Either way, I can't wait till winter now :)

Thanks!

Julian

http://outdoorsaunabuildmndiy.blogspot.com/

Chris Mills (author) from Traverse City, MI on March 11, 2016:

ALLY BABAY, Well, there is a question I haven't thought about in a while. All I can say at this point is that I remembering setting a budget of one thousand dollars at the time. I have to believe we came in under that amount.

ALLY BABAY on March 11, 2016:

How much did it cost you to build? Thank you for sharing this project.

Chris Mills (author) from Traverse City, MI on February 15, 2015:

chef-de-jour, sorry I missed your post from a month ago. Sounds like you had a workable sauna situation in Scotland. I'm away from home working on the road full time now and rarely get to use the sauna. But when I'm done out here on the road, I'll be relaxing quite often in the cozy warmth. Thanks for checking in here.

Andrew Spacey from Near Huddersfield, West Yorkshire,UK on January 12, 2015:

When I lived in Scotland many moons ago the rented cottage near Edinburgh had a sauna in the old cellar! It was electric and ate money but every so often I'd pop down for a good sweat and flush out. I love saunas- your conversion job is ace. A great family effort.

Chris Mills (author) from Traverse City, MI on October 11, 2013:

Jimmar, good for you. I hope you get many years of use out of your new sauna. It is so much more special when you have built it yourself. Thanks for stopping by.

jimmar from Michigan on October 11, 2013:

did it! turned that useless shack into something useable. I wish I read your hub before I started building. I just winged it, but wasn't too far off.

Chris Mills (author) from Traverse City, MI on March 18, 2013:

Randi, we had a blast working on the sauna. After we got it all finished, we went to the beach near here on Lake Michigan and collected basalt rocks to put in the cage on top of the stove. They hold the heat so that when we throw water on them, we get a rush of heat and steam. We really do enjoy our sauna.

Randi Benlulu from Mesa, AZ on March 18, 2013:

Interesting and impressive! What a great project!

Chris Mills (author) from Traverse City, MI on March 17, 2013:

mr-veg, Thank you for visiting my hub, and I am happy that you find it to be useful. Thank you for the vote and for sharing.

mr-veg from Colorado United States on March 17, 2013:

A Job well done !! Great work Chris and thanks for sharing such a nice and useful information. Voted up and sharing !!

Chris Mills (author) from Traverse City, MI on March 17, 2013:

Deb, we borrowed a table joiner and it worked like a charm. It is amazing how much can be learned if we are just willing to try doing these projects on our own. I'm proud of my sons for how motivated they were to attempt this project. So you did remodeling for a living? It is so gratifying to see an old home like ours take on new life. Ours was built in 1896.

Deb Hirt from Stillwater, OK on March 17, 2013:

What a fantastic project, Chris. Wow, had I only known, I would have been more than happy to do the cuts on my sliding compound miter saw. I have done MANY different kinds of cuts when I was doing remodeling for a living. I loved doing shiplap! Can't beat the smell of cedar!

Chris Mills (author) from Traverse City, MI on March 16, 2013:

Thanks Rosemary, It was a fun project, and using it never gets old. I hope someone who reads the hub decides to go for it and turn that useless shack out back into something they will use for years to come.

Rosemary Sadler from Hawkes Bay - NewZealand on March 16, 2013:

A great family project, you all worked hard on this and now you can all enjoy it.

A job well done and great instructions

Chris Mills (author) from Traverse City, MI on March 16, 2013:

Austinstar, that is a pretty good combo. Hot tub for relaxing the muscles and a pool to beat the heat.

Lela from Somewhere near the heart of Texas on March 16, 2013:

Oh, man, we have ice houses in Spades! When I was young, you couldn't throw a coke bottle 10 feet without hitting one.

But I do have an above ground pool (matches my double wide) and I recently purchased a hot tub spa. That's the best I can do.

Chris Mills (author) from Traverse City, MI on March 16, 2013:

Austinstar, I wouldn't recommend a sauna in Texas. Maybe an ice house would be more appropriate. Thanks for stopping by.

Chris Mills (author) from Traverse City, MI on March 16, 2013:

Eric, thank you. We had a great time working on the sauna. We each had a key role. Mine had to do with $$$. Now we enjoy taking saunas as often as we can together. I do have very good relationships with my sons. Go for it Eric. Make yourself a sauna. There is nothing like it for relaxation. Watch the temperature though. We had it up to 213 f a couple of nights ago.

Eric Dierker from Spring Valley, CA. U.S.A. on March 16, 2013:

Chris, do not take me wrong here; I got teary reading this article. It is awesome how you laid out the construction and the pictures fit in perfectly. I am contemplating doing one.

But it just got me all emotional to watch and learn of father and sons enjoying each others contributions and company. That is what it is all about!!

So I should say "my sons and I are contemplating"

Lela from Somewhere near the heart of Texas on March 16, 2013:

What a clever idea. Of course, living in Texas is like living in a sauna anyway. All you have to do is go outside. But yours looks very nice and cozy.

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