Thanks to the Finns — who’ve been sauna enthusiasts for centuries — sweating it out has become a popular practice in the Western world as well. Chances are, you’ve heard about the health benefits of saunas and now you want some of that goodness on tap in your backyard.
Before we dive into how to build a barrel sauna, let’s take a quick look at the pros and cons of going the DIY route. On the upside, it’s a fun project with longterm rewards and a decent amount of bragging rights.
On the down side, building a sauna from scratch is labour-intensive and requires a fair amount of know-how. If this is your first woodworking rodeo, a barrel sauna kit might be the better route to go.
While you won’t be able to claim the title of cooper, you’ll still have the satisfaction of putting something together with your own hands. Plus, you’ll get to enjoy your sauna a lot sooner.
Still want to make your own sauna? Let’s dive in.
What to Expect from this Guide
This guide will walk you through everything you need to know, from size and planning to the tools and various supplies you’ll need. We’ll look at lumber options (what wood is best and where to source it), assembling the sauna, building and installing benches and finally, heating.
Deciding How Big Your DIY Outdoor Sauna Will Be
Determining the size of your outdoor sauna will inform everything else, so let’s start there. Think about how many people are likely to use it at any given time.
There are other things to take into account as well, such as how much space you have available in your yard, the size of heater you plan on using, how much you’re willing to spend on electricity (if you’re not going with a wood stove), and so on.
For singles and couples a four foot deep two-person sauna is more than adequate. Depending on where you live and the time of year, something that size will take around 45 minutes to heat up. Why build something bigger and wait longer if you don’t have to?
What’s the Best Wood for a Barrel Sauna?
Western red cedar is the best wood for the job. Even a simple DIY outdoor sauna can benefit from its characteristics. It’s strong, it won’t warp or shrink, it has better insulation properties and it’s not hot to touch (useful in a sauna scenario).
As an added bonus, it also smells and looks good. It can be a little pricey though, so if your budget is on the tight side you may want to consider these less expensive softwoods:
- Common aspen
- Douglas fir
- Nordic spruce
A lot of people say you should only use wood that is completely clear of knots when building a barrel sauna, as the extreme heat changes and moisture levels could result in discoloration, warping and even breakage.
While it makes sense, ‘clear’ cedar is three times the price of its off-the-shelf counterpart. Since this build will be using 2×6s, there’s not really any concern for knots popping out of the wood like there is with thinner tongue-and-groove boards.
Building a sauna from scratch gives you the option of using locally and sustainably sourced materials. Along with being better for the planet, it can also be more cost-effective. Provided you’re not in a rush, you can search for specials online and at your local lumber yard.
A word of warning, be sure to steer clear of pressure treated lumber for the interior of your sauna. It’s been chemically treated and can emit toxic fumes when heated.
The Tools and Materials You’ll Need for the Project
Below is a comprehensive list of everything you’ll need for the build. Some tools can be substituted if need be, but this will serve as a good starting point for your DIY barrel sauna.
- Router table
- 1-1/2″ Round nose bit
- 1-1/2″ Bullnose radius bit
- 1/2″ Double flute straight bit (or a table saw with a dado blade)
- String or twine (4-5ft) and a pencil
- Standard carpentry tools
- Hammer and/or mallet
- Measuring tape
- 89 x 2x6x8 Cedar boards
- 51 pieces for the staves
- 16 pieces for the front panel
- 16 pieces for the back panel
- 6 spares
- 4 x 1x6x8 Cedar boards (for benches)
- 10 x 2x4x8 Cedar boards (for cross supports and bench supports)
- 200 x 2” Wood screws
- 100 x 2.5” Wood screws
- 2 or 3 Aluminium straps +-250” (optional)
- 2 x Door hinges
- Sauna stove
How to Build a Barrel Sauna: Part 1
We’ve broken the process down into two parts. The first focuses on preparing the staves and dado joints. In the second, we’ll focus on the walls, door and cradles.
Preparing the Staves
DIY sauna barrel builds typically use a bead and cove joint for the staves, as it serves the dual purpose of ensuring a snug fit while still allowing enough give for the barrel shape.
To do this you’ll need to run your boards through the router table using 0.5” radius bead and cove router bits starting with the bullnose (convex) side. This will create a small shelf for the hinge to seat properly.
You’ll need to run each board through the router a total of four times. A shaper tool can then be used to remove any rough spots from the bullnose side of the stave.
To prevent water from leaking, your bottom stave should have two convex edges and the top stave two concave edges.
Preparing the Dado Joints
Once you’ve routed all your bead and cove joints, the next step is to make dado cuts into the staves. The front and end caps will then fit snugly into these joints.
The dado cuts should be .75” deep and 1.50+.05” wide (based on using planed lumber with a 1.5” width).
While you can use a dado blade, we’d advise against it if you’d rather not lose any of your fingers. Using a dado blade requires you to remove the table saw’s safety cover and has a high potential for deadly kickback. Not a good combination.
A safer alternative is to use your router table with a 0.5” straight flute router bit instead. This will take 3 passes (moving the fence 0.5” each time), but is much safer than the dado blade.
To ensure everything is properly aligned, cut the first dado joint 3” in from the end of the stave. For the second dado joint cut, measure exactly 90” from the first dado cut.
Doing this ensures that the front and back panels will fit well even if there’s a slight variation between board lengths. For more details on preparing the staves and dado joints take a look at my personal blog.
Building a Barrel Sauna: Part 2
Once you’ve taken care of the staves and dado joinery, it’s time to make the other parts of your sauna. In this section we’ll cover the end caps (walls), door, cradles and straps.
Build the End Caps (Front and Back)
To build the front and back panels you’ll need to route tongue and groove joints in 2x6x8s to build two squares that are sixteen boards wide respectively.
Remember to rough cut some of your boards so you have them on hand for the top and bottom sections, which aren’t as long as the middle.
Once you’ve assembled the two boards it’s time to cut them into circles. Having a template to run your router around is ideal, but if you don’t have one you can also use a circular saw to do the job.
The easiest way to make the door for your outdoor sauna is to first make the wall and then simply cut out the door and frame it. How big you make it is up to you, just make sure you leave at least 3-4” of material in the corners between the door frame and the edge of the circle.
This will make provision for the 2 x 4” cross braces required to keep the end cap as one piece. If you’d like your sauna to have a window, the door is the best place to add it because it means you won’t have to worry about additional structural framing of the walls.
The sauna feet or cradles can be cut from 2×8s and 2×10s. When you’re ready to assemble the sauna, mark out a rough curve for the feet based on a radius .75” larger than the end caps.
Because the staves have a .75” deep dado joint, the outside radius of the sauna will actually be 39.75”. Use 2.5” wood screws to connect the bottom eight or nine staves to these feet (more on this in the assembly section).
Prepare the Location
Preparing the location is an important final step prior to assembling your sauna. It’s imperative that you place your sauna on ground that’s both solid and flat. This could be a concrete pad, solid deck or a gravel base. If the latter, make sure it’s been well tamped.
If you plan on placing the sauna and leaving it, then making the extra effort on the base makes sense. However, if the plan is to have it at home during winter and then move it to wherever you spend your summers, you can afford to be a little less fastidious in this area.
Assemble Your Sauna
Now we’re getting to the fun stuff. It’s time to round together all your separate components and assemble them into an outdoor barrel sauna you can be proud of. You’re going to need:
- 2 x Cradles (more if your sauna is longer)
- 2 x Walls (plus one extra for a changing room)
Place the Cradles and Set Your Staves
To assemble the sauna, start by lining up the cradles. Screw in enough staves to cover the cradles. Tap them gently but firmly into place to ensure an even, tight fit. It’s important that the dado joints are perfectly aligned.
Set the Walls
Next, you’ll need to find someone to help you drop your end discs right into the dado cuts on the staves. From here, temporarily add a couple of staves to the top of the discs to stop them from moving or falling.
At this point it’s also a good idea to make sure the walls are perfectly straight, especially on the door side.
Insert the Staves
With that done, place the remainder of the staves (alternating sides as you go) until you reach the top. Keep a keen eye on the dado joints to make sure they’re lining up perfectly.
In a perfect world you won’t have a gap at the top, but if you do find there’s a small gap you can fix it quite easily by simply tightening the straps.
You can use straps to bring the whole thing together, but we found that screwing the staves into the end caps with 2 x 2.5” screws eliminates the need for them.
Straps do have an aesthetic appeal however, so it might be nice to add them anyway. They’re not that expensive and you may even find your local hardware has banding they’re looking to offload.
Building the Benches
It’s a good idea to wait until you’ve assembled your sauna before designing and building the benches. Being able to actually stand inside it and see where the stove is will give you a good feel for the type of benches you want to put in there.
Custom sauna benches need to be sturdy and functional, but there’s no reason you can’t still get creative with the design. Just keep in mind that your feet should be the same height as the stove’s rocks in order to make the most of the heat.
The wood you choose should be moisture-resistant and respond well to heat. Cedar is the best choice for more than just its good looks, but it’s not the only option. Aspen, pine, spruce and alder also do well.
It’s Time to Dial Up the Heat
We’re on the home stretch. You should know by this point whether you plan on using an electric or wood fired stove. Whichever you go with it will need to be installed in accordance with local codes as well as the manufacturer’s guidelines.
This is especially important when it comes to wiring your electric sauna. If you’re not comfortable doing this part yourself, it makes sense to hire an expert. It’ll cost a bit extra, but in the long run it’ll save you.
While it is possible to build your own sauna stove, getting efficient air flow isn’t that simple. Since the Finnish stove makers are experts at this, we recommend shelling out on a Harvia stove. Even their smaller M1 model will get this type of sauna up to 95ºC.
If you’re on the fence about spending the money, consider this. Would you rather turn on the heat and sit back and relax or do you want to spend all your time fiddling with your wood fired stove to achieve the right temperature?
Going the Extra Mile
Below are some extra things that could ultimately take your barrel sauna build to the next level. While not entirely necessary and very much dependent on the availability of time, space and finances, you’ll find them worth it in the long if you plan on having regular saunas.
How About Some Changing Room?
If you live in a cold climate and plan on saunaing in winter (which is kind of the point), building a longer sauna so you can use the first four feet as a changeroom is a gamechanger. It’ll make disrobing for the sauna more comfortable and it’ll keep the heat in.
For this to happen you’ll need two front end caps (walls) and two doors. You won’t need anything else in the changeroom space aside from some hooks for your clothes and towels. You could add a bench if you like, but it’s not necessary.
Taking the Cold Plunge
Alternating hot and cold is arguably one of the best parts of saunaing. If you don’t have access to a lake or river, adding a water barrel shower or even a lofi bucket and string shower just outside the door of the sauna is a great way to cool off.
Other nice-to-haves are a thermometer, a timer and some ambiance-enhancing lights.
In the beginning at least, knowing exactly how hot your sauna is can come in very handy. Although, you will eventually be able to gauge by feeling alone.
Since it’s not ideal to stay in the sauna for extended periods of time, setting a timer is key. You definitely don’t want to risk dozing off in there.
With regards to lighting, it’s important that whatever you choose can withstand the heat and won’t melt or worse, explode, when exposed to the high temperatures.
All That’s Left Is to Get Sweaty
Now that you know how to build a barrel sauna from scratch all that’s left to do is get busy. If, on the other hand, you’ve come this far only to conclude that a barrel sauna kit is the better option, why wait?
Whichever route you go (DIY or kit), now is always the best time to get sweaty.