Sauna Design

Sauna Design

The design for this sauna had been floating around in my head for many years. In fact, I had started designing and drafting it out more than 15 years ago. However, my wife wasn't keen on losing our deck for this project, although more recently she realized that we really didn't use the deck much and perhaps a sauna would be a better use for this space.

My early sauna designs had an electric sauna stove and a shower stall with hot and cold running water, and a drain system routed back to our laundry room. This design was much more complex and in the end we decided to go with a wood fired sauna using more traditional Finnish bathing methods (hot water warmed by the stove and bathing done with buckets and cold rinses).

With the simplicity of the design we also chose to create a feeling of an old time traditional sauna with the choice of our materials and décor. 

However, the proper functional design of the sauna itself is even more important than its form. Careful consideration was taken in the bench design, ventilation, stove inlet air,  safety issues, and how the steam would travel unimpeded from the stove to the individuals sitting on the bench.

I still had access to an AutoCAD program so I used my CAD design and drafting skill into use by laying everything out beforehand. This allowed me to electronically measure roof rafter cuts, etc. and make estimating more accurate.

As detailed on the sauna bench design page, we wanted benches situated in such a way to give us maximum heating potential. We also wanted them to be designed in such a way to give us comfortable sitting options. 

Proper ventilation will improve the sauna experience by providing the proper supply of fresh air for the sauna user. 

Strategically placed inlet air will provide for proper sauna stove burning and lölyl distribution.

We provided curved transitions between the walls and ceiling to provide an even flow of heat and steam to the upper bench area. This effort was labor intensive but well worth the time.

Dream Design

Before I retired I was a Sr. Process Designer for various engineering firms throughout my career. One of my primary duties, and the one I enjoyed the most, was doing preliminary layouts for water and wastewater treatment plants and then fine tuning them into a final design. The design process could take several months depending upon the complexity of the project. At times when I was stumped on a design issue I may have thought about it before going to bed and I would toss around several design possibilities in my head while falling off to sleep. Often I awoke in the morning with a design solution now in my head and I couldn't wait to get to work to see if it would be feasible.

This same "Dream Design" approach was utilized during the design of this sauna. I tried to work through various design and construction issues I may encounter and try to find a solution to them before the actual construction. By building the various pieces of the sauna in my head first, step by step, I often discovered issues that may arise and cause conflict during construction. If you're thinking of building a sauna I suggest you also try to think things through as much as possible instead of trying to wing it. With the cost of building materials mistakes can be expensive and time consuming to repair or replace.

Safety Considerations in Our Sauna Design

Safety was also a major consideration of our sauna design.  After our sauna was completed we invited our State Farm insurance agent to tour our sauna. He took measurements to assure that we had adhered to clearance distances and gave us a big thumbs up on it's  design and construction!

• We used mineral wool insulation for the sauna walls and ceiling because of its good insulation values, resistance to moisture, and also its high heat and fire tolerance (2000 degrees F). 

• The insulation then was covered with a foil and all seams were sealed with heat resistant tape for thermal and moisture containment.

• The walls adjacent to the sauna stove were covered with foil, clad in 1/2" thick cement board, and then covered with porcelain tile to create a non-combustible surface 7 feet high adjacent to the sauna stove. Clearance distances, as recommended by the sauna stove manufacturer, were adhered to from the stove surfaces.

• The sauna stove also had heat shields on sides adjacent to the sauna walls which provided additional heat protection.

• The Kuuma sauna stove is the only wood burning sauna stove on the market that is UL approved (#1482 by PFS Corporation). 

•  A 6" diameter double wall (black enamel pipe on the outside and stainless steel pipe on the inside) stove pipe extends from the stove to the ceiling. Each pipe section is secured with 3 screws. At the ceiling, a decorative and protective cover which is securely attached to the ceiling joists, supports the Class A chimney above. 

• The Class A chimney is a double wall insulated chimney pipe that allows a 2 inch clearance from combustible materials.  The Class A chimney has an attic heat shield system above the ceiling to help assure that no insulation or other combustible materials come into contact or close proximity to the chimney system. The chimney extends to about 4 feet above the roof and ends with a rain cap and spark arrester screen. Proper clearance distances were maintained throughout the structure. 

• The stove was placed on a 36" x 36" x 2.5" thick non-combustible concrete surface made from large concrete pavers.

• A sloped (2" - 1" thick) concrete floor was poured with a drain system to help assure there would be no standing water on the floor. Non-slip pebble stone type tile was laid over the concrete floor to limit slipping on the wet surface.

• A stable two step stool was fabricated to allow easier and safer access to the sauna benches

• To help facilitate safe access to the top benches a grabrail was affixed to the wall adjacent to the benches.

• The floor of the changing room was fabricated from waterproof vinyl laminate flooring to help ensure longevity and a non-slip surface. This floor was placed on a slightly higher elevation than the sauna room floor to help prevent water from entering the changing room.

• A fire extinguisher was placed in the changing room near the exterior door and we also have another large fire extinguisher in our home.

• Ashes from the sauna stove are placed in a covered metal bin and stored outside.

• Igneous rocks were collected from northern Minnesota and Wisconsin to use as the sauna rocks. These types of rocks are the most durable and can endure the extreme sauna conditions. Other types of rocks may tend to explode when hot and water is thrown on them.

• A temperature sensor which showed the temperature at ceiling level above the sauna stove could be read through the candle window by people sitting on the sauna benches. This temperature reading could also be read remotely from inside our home via a Bluetooth connection. This feature allows us to remotely monitor the temperature of the sauna. A high temperature reading will also produce an alarm to notify us of potential too high heat issues.

• An air ventilation system to provide an adequate flow of fresh air and mix it well with the air already in the sauna. The ventilation system is also used to slowly cool off the sauna after using it. An adjustable air inlet and two outlet ports were incorporated into the design to give the user the most flexibility in fine tuning the proper air flow. The air inlet is located low to the floor adjacent to the sauna stove and also provides combustion air for the stove.

• There are two lights located in the changing room. The electric lantern hanging in front of the candle window provides light for the sauna hot room and the changing room. If more light is desired in the changing room, an additional wall sconce light provides additional lighting.

• No AC electrical items were located within the sauna hot room area. Adjustable (brightness and color) low voltage DC LED light strips are located below the top bench to create the lighting ambiance we may desire. The DC transformer is plugged into a switchable outlet located in the changing room.

• Electrical power is routed to the changing room from the house through aluminum electrical conduit to avoid any rodents from chewing on the electrical wires

• A ground fault electrical receptacle is located in the changing room as the first electrical receptacle and thus provides protection to all other electrical items located further along the electrical circuit.

• The candle window is made with tempered glass which can withstand the high heat of the sauna.

• The exterior window in the sauna hot room is made from 3.5" thick glass block units which can withstand high temperatures.

• The sauna benches and stool are fabricated from red cedar. No exposed screws or nails are visible to avoid sitting on a hot metal surface.

• Unlike many modern saunas you may see today, the area between the top and foot bench was not enclosed to provide better air movement throughout the sauna.

• A foot rest rail, which also doubles as a safety rail, was provided on the foot bench to protect bathers from coming into contact with the hot sauna stove.

• The wood door handles on the sauna door were made from Japanese Yew wood and are not has hot as metal door handles would be.

• The sauna room door swings out to allow a person to quickly exit the room if required. A spring helps keep this door shut.

• I had assumed that building permits were required for structures over 100 square feet in the city we live in. This structure is 96 square feet.  (I found out afterwards that the structure limit is actually 200 square feet) However, building codes were met or exceeded in the construction of this structure. The neighbors that live on both sides of us were also very supportive of this project.

• Maybe not a safety issue as much of a convenience issue, is the ability to drain the cold water line which supplies the sauna with water to the laundry room floor drain. This is especially helpful in the winter when this line would freeze if left filled with water. A heat tracing line was also added to this water line and additional pipe insulation added to prevent freezing of this line during the winter. Even though the heat tracing is supposed to be good for -40° F we still drain the line in the winter after each use.

Sauna Design Resources on the Internet

There are actually quite a few sauna design resources on the internet and in books, plus the advice of fellow sauna builders and Facebook groups dedicated to the design and construction of wood fired saunas.

A very useful website for sauna design is Trumpkin's Notes on Building a Sauna.  This is a book length manuscript with a lot of good information about sauna design.

Although he is not Finnish, Glen Auerbach has become quite knowledgeable about sauna design and customs and is a huge advocate of the Finnish wood burning sauna. His website, saunatime.com, is full of a lot of useful information about sauna design and culture. Glen also offers an eBook about sauna construction for $25. Although I ordered the eBook,. I used many of my own ideas on floor and bench design.

There are a lot of Facebook groups dedicated to the design and construction of wood fired saunas.  I often turned to others with questions and gleaned from them what worked or didn't work. You often learn from your own mistakes, but you can also learn from the mistakes of others too.

Facebook Wood-Burning Sauna Group

Facebook Sauna Design, Construction, Use, and Enjoyment Group

Facebook Wood Fired Saunas Group

Check out the Finnish Sauunologia.fi website to learn more about the Finnish sauna culture in regard to the sauna values, practices, and respect. The website also has information on the variety and history of the Finnish sauna, sauna stoves, air quality and ventilation solutions, and interior design of saunas. The author (Lassi Liikkanen) of this website is also the author of an excellent book on Finnish sauna design discussed more below.

Sauna Design Books

My brother, Steve Leppälä, loaned me two of his sauna design books and both of them were very informative on building a traditional Finnish wood burning sauna. I would highly recommend that they be read before you design and construct your own sauna. There are a lot of considerations that many people don't think about, such as material selection and ventilation in the design  and  construction of a well built sauna.