Outdoor 110v Sauna

I built a small outdoor sauna with limited experience. I was determined to sweat and I'm thrilled with the results. This blog will share my process for researching, designing, constructing, and finishing a small outdoor sauna with a 110v heater.

The sauna was built from scratch with an emphasis on ensuring quality and keeping costs as low as possible. I am very grateful for all of the research, planning, design, and significant support from friends and family who helped to make this idea a reality.

The idea to build my own sauna started when I was settling into a long drive, looking for something to occupy my mind. The COVID-19 pandemic had meant my local gym was closed for months, and I was truly missing the sauna.

I started by shopping for prebuilt saunas or sauna kits, and there is a wide variety of options available. However, most of the options I preferred were expensive and presented logistical problems. As I began to think through the process, it became apparent that building a sauna from scratch was the best option for my needs.

I knew I wanted to build a small sauna that could be heated up to 180 degrees. I really wanted cedar for the interior. The tongue and groove cedar from a nearby lumber yard turned out great! After wrapping up this project, I am happy to report the sauna heats well and works better than expected.

Here are a couple of helpful links I visited along the way:

Sauna Times

Sauna kits and instructions

Five traits for sauna design

Sauna basics video

I spent a lot of time thinking through the logistics and feasibility of building a small outdoor sauna. I had the space available on a concrete pad next to the house, which worked perfectly as a level and reinforced surface to build upon.

Selecting the heat source for the sauna was the most important decision for the overall design. And it was difficult to settle on the perfect heater. I started by shopping for a heater that was:

• an electric wet and dry heater
  • I enjoy the steam or löyly that comes from pouring water over the rocks.
• and reasonably priced
  • As it turns out, most new electric sauna heaters are expensive.

The Ah-ha! moment:

Most sauna heaters run on 220v power, but I had an existing 110v outlet easily accessible. I decided to shop for a 110v electric sauna heater. After a great deal of searching, I found only a few options and exactly one unit that was modestly priced. The sauna heater had very mixed reviews and I was reluctant to design the entire project around a heater that didn't perform as desired. (the product manual is attached).

The 110v heater had the obvious trade-off of less power, meaning it was only capable of heat up a very small space. The manual says the heater works for an area of 105 cubic feet or less, or about the size of a small closet. I decided I would scale down the size of the sauna, prioritize insulation, and hope the bad reviews for the heater were based on poor insulation or trying to heat up too large of a room (i.e. more than 105 cubic feet).

*After using the sauna for a few months I would say there is barely enough space but can fit two people in the sauna.

The rest of the planning phase became more tangible after determining what heater I would use in the sauna. The sauna design was based on the dimensions recommended in the manual for the 110v heater (105 cubic feet or less). I used excel or google sheets to convert the L x W x H dimensions into cubic feet and settled on a 5 ft x 3.5 ft x 6ft. The roof is pitched, so I averaged out the height with a front height of 6ft 3inch and a back height of 5 ft 8in.

I worked with a friend to develop technical plans for the sauna. This step was a huge help and a serious effort! At this point in the process, the reality of how many tools, supplies, and plan elements that would need to be involved in constructing a sauna suddenly became obvious...and a bit daunting.

• How tall should it be?
• What about ventilation?
• How should the roof look?
• It should have a window, right? But maximizing insulation and heating efficiency is a priority number one?
• What about the base?
• would you be able to move it?
• Is there special insulation for a sauna?

Along the way, it became helpful to envision the build in two phases. First I would plan, buy materials, and construct an exterior structure. Essentially building a small shed. And then I would design, buy materials and finish the interior to build out the sauna.

Materials for Sauna Exterior

• 2 x 6 Green Treated lumber (base)
• 4 x 8 3/4" OSB (floor)
• 4 x 4 Pressure Treated lumber (skids)
• 2 x 4 construction grade lumber (frame)
• R13 Pink insulation with backing
• 4 x 8 1/4" OSB (walls)
• Dual Paned Insulated Shed window
• Tyvek house wrap

I knew the interior dimensions of the sauna would be 5 ft wide x 3.5 ft long x 6ft height and then framed out the structure based on those dimensions. The 2 x 4 studs were spaced out about 14 inches apart, except for the doorframe and the window. I included a top plate and bottom plate for all four walls and the roof.
*Placing studs 14 inches apart worked great for installing the R13 insulation.

Based on research, I learned I should weather wrap the structure. This has the dual benefit of protecting the sauna from moisture and the elements as well as providing an additional layer of insulation. This video was great and shared a helpful trick for completing this step alone. With a clamp, broom, and stapler wrapping the entire sauna was a one-person job.

I decided a window would be an important feature to help add light, a view of the yard, and less claustrophobia to the sauna. I was looking for a small double-paned and insulated window, and eventually found what I was looking for shopping for shed windows (see link above).

I started working on the interior by installing R13 insulation and an aluminum foil vapor barrier. The process was straightforward using a utility knife, staple gun, and work gloves.

*I highly recommend using an aluminum foil vapor barrier, it helps to keep heat in the sauna and moisture away from the structure.

I found the 1x4 t&g cedar boards at a local lumber yard. The boards were 8 feet and the lowest priced/grade cedar available, and it turned out beautifully. The job was made much easier with help from family and friends. I was also incredibly fortunate to be able to borrow a chop saw, jigsaw, and Paslode compressed air nail gun. I used these power tools extensively during the build.

I enjoyed designing the layout of the sauna and found myself making several additions as I became more familiar with the space. The key considerations for the interior were installing the heater and the design of the bench.

I asked a friend who had significant experience with electrical work to help install the heater. The manual provided straightforward instructions and the Amazon product page provided a very instructional video.

Bench

The key dimension to consider for any sauna is the distance from the ceiling to the upper bench. This should be 44 inches, +/- 2 inches. If the benches are too low, the heat and löyly will remain above your head. If your sauna is very high, you either need to lower the ceiling, or have high benches. High benches are great, but you need multiple steps in order to climb up, which is incredibly difficult to achieve in such a small space. A normal sauna inside height is 88 inches and the upper bench is thus 44 inches from the ceiling, and the floor. The typical bench depth is around 24 inches.

I used leftover t & g cedar for the bench slats. My dad was kind enough to use his woodshop to cut the slats down to size, sand them, and round over the front...thanks, dad!

Venting

Ventilation is a really important detail. Ventilation allows new oxygen into the sauna, without which you will quickly begin feeling uneasy or lightheaded. The heater manual provided directions for ventilation.

Additional elements

Several elements were added to the sauna after getting to know how I used the sauna.

• Guard rail around the heater
• Magazine rack
• Foot rest / water bucket storage
• Towel / clothes rack
• Phone holder (the small wood box works also works as a speaker)