Building a backyard sauna has been one of the most rewarding DIY projects I’ve ever undertaken. After months of planning and construction, Ziggy and I finally have our very own Finnish-style sauna in the backyard. Not only is it a cosy and relaxing retreat, but it was also surprisingly affordable to build. In this blog series, I’ll walk you through the entire process, from initial design through to the sauna sessions. We managed to create a four-person sauna for under $5k AUD. I’ll share things I learnt along the way to help you achieve your own backyard hot box.

This is the first part in a series of 4 posts. This post is a general overview of the project, further posts will elaborate on the design, build and operation of the sauna.

These are all of the planned posts:

• Part 1: Project Overview (this post)
• Part 2: Designing a Sauna (coming soon)
• Part 3: Building the Sauna (coming soon)
• Part 4: The Finished Product (coming soon)

Origins of the Sauna

My friend and housemate Ziggy spent much of last year in Canada on a remote mine site with a sauna. This fostered his love of the heat. Upon his return to Tasmania I was in the midst of a heat acclimation protocol for the GPT100. I was going to a nearby sauna daily. Ziggy accompanied me on many of these sessions. While we sat there sweating profusely we discussed the merits of having our own sauna at home. This is where it all began. The idea grew from here.

We began scouting around the house for a location. We settled on a concrete slap in the garden that up till that point mostly served as a wheelbarrow storage area. With a location in mind we began working on the design.

Planning and Design

Designing the sauna was a long and arduous process. The design evolved and improved over many iterations. My first concept was totally misguided. I thought we could just build a small shed and mount a heater in it. Ziggy and I gradually went down rabbit hole after rabbit hole learning about sauna design principles. We read books, blog posts and the r/sauna subreddit. We quickly become converts to the Finnish style of sauna and became obsessed with building the perfect sauna for optimal löyly.

The key components of a good Finnish sauna experience are:

• Heat
• Air quality
• Interior design
• Culture and company

In my next post I will elaborate on how we optimised our design to meet these criteria. The only thing we couldn’t control in the design process was the culture and company. That part comes later.

We decided to build a 4 person sauna. This seemed to be the right size for us and it fit the space available. The most tedious part of the design process was settling on the overall dimensions and layout. We had to make our design fit in the space available and within council height restrictions. Thankfully there is plenty of guidance in the Secrets of Finnish Sauna Design by Lassi A. Liikkanen on recommended dimensions. The key dimensions flowed on from the rules set out in the book.

We decided to use an electric heater for convenience of operation. Since we anticipated regular usage we didn’t want to be lighting a fire every time. The heater size is governed by the volume of the room. Our room required a 6kW heater. We were able to source this locally from an importer called Shym Saunas. The next points of deliberation were on the materials to use for construction, the insulation, bench sizes, ventilation etc. I will save all of this stuff for my next post about sauna design.

Once Ziggy and I finally settled on the overall dimensions and materials I got into detailed modelling of the structure. I work with Rhino everyday at work so I am quite proficient at 3D modelling. It didn’t take me long to have the whole thing modelled and construction drawings ready to go. From these drawings we did a material take off and looked into procuring materials.

Recommended reading:

• Secrets of Finnish Sauna Design
• Trumkins Notes on Building a Sauna
• Trumkins Notes Long Form
• Sauna Times Blog
• r/Sauna Subreddit

Partnership Formed

Living in a rented share house makes building a backyard sauna difficult. The house is owned by Ziggy and Miranda, so permission from the landlords was easy to obtain. Miranda was initially ambivalent but is now a convert to the Loyly. The other housemate James was more than keen for a sauna in the backyard.

The main difficulty was me being a partner in the project with Ziggy. I was going to be the part owner of a sauna that lives in the backyard of someone else’s property. So we drew up a short partnership agreement whereby we split all expenses for 50/50 sauna ownership. If I move out Ziggy buys out my share minus a bit of depreciation. It seems over the top to have a contract but it’s easier to agree on these things now than down the track. These little things can save friendships.

Once Ziggy and I signed our contract we began buying materials and the project was officially happening.

Materials and Supplies

The first thing we ordered was the heater and I picked it up from Launceston. Then we spent a long time deliberating on design and materials before placing a large Bunnings order that we had delivered. It would have been better for us to source our own materials so we could choose better timber. But we had no way of transporting heaps of timber to delivery was the easiest option.

At the design stage I was always thinking about materials and stock sizes. Working at a shipyard by day I am used to trying to minimise wastage. The roof length is exactly the same as the stock length colourbond, the walls and ceiling are almost exactly the stock length of radiata pine and the stud spacings on the walls line up with the width of James Hardie eave sheet.

We were able to scavenge a few bits and pieces. A workmate Phil gave me some cement sheet for cladding that was lying around in his yard. Another colleague Andrew donated a double glazed window that ended up mounted in the door. On top of our initial Bunnings order there was countless additional Bunnings trips additional bits and pieces.

💲 Cost Summary

Item	Cost
Heater	$910
Bunnings order	$2260
Additional bits and pieces	$1270
Heater wiring	$550
Total cost	$4991

The Build Process

Before we could start building we needed to source a lot of tools. I didn’t want to buy them for a once off project so I asked around and was able to borrow all sorts of tools. It helps when you work at a shipyard with lots of tradesmen.

The first step was preparing the site. Since we were positioning the sauna on an existing slab we only needed to clear some foliage and put some gravel in the garden bed. The sauna overhangs into the garden a bit so we put a row of bricks to support the outer edge.

With all of the materials and tools ready we kicked off the build with a big weekend work session. We managed to get all of the framing together. If we knew what we were doing it would have been a lot quicker. Things take time when you are learning on the job and making many mistakes along the way. The following weekend we had the floor fixed down, the wall and roof framing stood up and even got the roof iron on. This was a fun stage where the sauna materialised with lots of visible progress.

Progress slowed the following weekend with Ziggy back at work. I toiled away adding the external cladding. Working with cement sheet was surprisingly easy. We used eave sheet for a lot of the cladding and designed the stud spacing to suit the cement sheet sizes which reduced the amount of cutting. This also made handling a lot easier.

Upon his return, Ziggy started putting the insulation in. He works FIFO in mining so when he’s home he’s around all the time. So he got most of the insulation in during the week while I was working. I was happy because I hate touching the stuff.

With all the insulation in place, we wrapped the internals with moisture barrier foil and added timber battens. This is an important sauna design detail that protects the structure and insulation from the heat and moisture. The timber battens allow for an air hap behind the internal lining to prevent to build up of condensation that will degrade the timber.

Ziggy headed back to work and I kept working on installing the internal lining. We thought this part would be easy but it turned into a frustrating labour-intensive process. The radiata pine tongue and groove was warped and bent making each panel a battle to get in. I used straps to hold each board down before fixing it off. On the ceiling we used a wedge and dog system to lock each panel in.

I became obsessed with getting it done, putting in a hours after work each day. I made good progress in a short time span. When Ziggy returned there was just the front wall and ceiling to do which I let him do because I was so sick of it.

With the internal lining finished it felt like we were almost done. But this was far from the truth. There was still so much of the fiddly stuff to be done. I drew up the benches and Ziggy got onto making them while I went deep into door design and construction. I spent a week thinking about how to make the door before I started designing it.

Once I finally worked out how I’d make it I got to work. It was probably the most difficult part of the whole project for me but also most fulfilling. We also added many finishing touches such as ventilation louvres, external trims, mounted the heater, and installed the benches. Ziggy added a waterproof membrane to the floor to protect the plywood from water.

The final piece of the puzzle was getting a sparky to hook up the heater. Due to the size of the heater it needs it’s own circuit breaker on the main switchboard. Our switchboard was too old and full to fit the heater so we needed a switchboard upgrade.

I arranged for Benny the electrician from work to come over and do the install. The hard part was pinning him down to come out and do it. After being delayed countless times Benny finally got over to upgrade the switchboard and hook up the heater. By this stage, the sauna was ready to go!!

⏲ Build Timeline

Date	Acticvity
19 March 24	🚚 Material order delivered
5 April 24	🚩 Started build
13 April 24	🏚 Framing complete, wrapped and roof fitted
19 April 24	🔨 External cladding fitted
1 May 24	🔨 Internal insulation fitted and foil lining
5 – 14 May 24	🔨 Internal wall cladding
7 – 22 June 24	🚪 Door and benches assembled
13 June 24	🔥 Mounted heater, installed benches and door
16 June 24	🥵 Heater wired in, practically complete ✅ first test run!!
Total time to construct	89 days*

* Both Ziggy and I work full-time and still run a lot. If you knew what you were doing and had spare time this could be built in less than a week.

The Finished Product

We had our first sauna session the same day the electrician switched the heater on. I sat there pouring out sweat feeling immense fulfilment with the finished product. The sauna was on every single day for it’s first week of operation. Everyone in the household was enjoying it along with the many friends that wanted to get involved.

Now after a few months of usage it is still running well. We have been able to get it up to 94 degrees Celcius and in our opinion it makes good Loyly. The cold plunge has also been getting a workout. We fill a downstairs freezer with blocks of ice and use a cold plunge between sessions to reach maximum euphoria. The cold plunge has been worked so hard that it now has many leaks. This will probably spur on the next project of making a chest freezer cold plunge.

I will do a whole post on the finished product, reviewing the design and functionality. We have been experimenting with ventilation arrangements and working out how long it takes to heat. We are thrilled with the finished product and have only experienced minor issues.

Summary

Overall, the sauna build project has been a great success! It took us around 8 months from inception to first sauna, and cost a total of $4991 including the heater and wiring. We’re happy with the outcome and can’t wait to share more about the design, build, and use of our sauna in future posts.

Stay tuned for more!

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Planned posts:

• Part 2: Sauna design (coming soon)
• Part 3: Sauna build process (coming soon)
• Part 4: Sauna in action (coming soon)