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Acquiring a Sauna
The Frame
Lamp Guard
Filling the Gaps
Change in Plans
The Door
The Vent
Final Touches
Sauna Sessions
Effects and Results

The Frame
Page Three

I began with the idea of using Dr. Wilson's sauna frame design, but modifying it to use a wooden frame and insulation. His PVC frame is built in the shape of a trapezoid that is two feet wide on one end, four feet wide on the other; and five feet high. After considering how to build a frame in this shape, out of wood, I decided to use a rectangular shape, four feet wide on both ends, and five feet high, which would be easier to build, since the corner joints would join together at 90 degree angles.

However, after measuring my available space, and consulting with Dr. Wilson, I decided that his shape would be the better choice, because it would take up less space, and the smaller volume would make it easier to heat it, and easier to maintain the high operating temperatures needed.

If the back end is four feet wide, it allows enough space for a door, and enough leg room to rotate around, on a stool, in a complete circle during a session. At five feet high, it is high enough to allow easy entry, from a standing position, and plenty of head room when inside. Making the other end of the unit two feet wide is large enough to mount the three lamps, and also keeps the trapezoid wide enough to move around inside it comfortably.

PVC Frame:  Infrared-Lamp Sauna
Dr. Wilson's PVC frame design.

The Details

There were many things to consider when designing a wooden frame for this sauna. The book pointed out that some materials would be unsuitable, because they might out-gas toxic chemicals during operation, and others were impractical for other reasons. After considering many options, I decided to use 2x2’s for the frame, and 1/8” hardboard, attached to both sides of the frame, for the walls, bottom, and top. This would leave a 1 1/2" space between the two sheets of hardboard for Styrofoam insulation, and an air gap, which should be sufficient to keep most of the heat from escaping.

However, after my first visit to Home Depot, and McCoy’s, it was clear that the 2x2’s, that they were selling, were not nearly straight enough for a project like this. Their 2x4’s were somewhat better, but Home Depot couldn’t rip them into 2x2's, so this was not a practical solution, because a 2x4 frame would be much larger and heavier than needed. Finally, I found some decent 1x4’s that just might work. A frame made of 1x4's, aligned on their edges, would cut the space between the two sheets of hardboard to 3/4", but if it was filled with a sheet of Styrofoam, it should do the job.

Since the inside dimensions of the frame would be two feet on one end, and four feet on the other, I needed to compute the lengths of the other two sides, and the angles for each corner. Using the fact that a Trapezoid is just a Rectangle, with a Right Triangle on either side, I needed the geometric formulas for Right Triangles to make these calculations, so I found a program that would do it for me.

Drawing of Sauna Frame: Infrared-Lamp Sauna
This Trapezoid is just a 2' x 4' Rectangle
with a Right Triangle on either side of it.

With this diagram, it is easy to see the 2' x 4' rectangle, and two Right Triangles, that have a 1' side and a 4' side, that make up the Trapezoid. The Hypotenuse of the Right Triangles must be determined, along with the two remaining angles, to calculate how to cut the 1x4's. The 90 degree angles of the Rectangle are already a known quantity.

Wahoo's Kewl Calculator, available at no cost from, plug "4" into Side (a), and "1" into Side (b), and then hit Calc It, with the following results:

Wahoo's Kewel Calculator: Compute Right Triangle
The calculator computes Side (c) and the two angles.

Now, we know that Side (c) must be 4.12 feet, which is 4 feet and 1.44 inches, or about 4 feet, 1.5 inches. We also know that Angle (A) is 14.0362 degrees, and Angle (B) is 75.9638 degrees.

Note, at the top of the previous diagram, that the 14.03 degree angle must be added to the 90 degree angle of the Rectangle to get the total span of 104.03 degrees. This means that the two boards in the frame, that will form this angle, will each be cut at 104.03/2 = 52.01 degrees.

The 104 degree angles for the frame: Infrared-Lamp Sauna
Cut each of these two 1x4's at 52 degrees
to form a total span of 104 degrees.

The 75.96 degree angle describes the total span, so it is not added to an angle in the Rectangle, therefore the two boards in the frame, that will form this angle, will each be cut at 75.96/2 = 37.98 degrees.

The 76 degree angles for the frame: Infrared-Lamp Sauna
Cut each of these two 1x4's at 38 degrees
to form a total span of 76 degrees.

I knew that one of the most difficult parts of this project was going to be cutting these angles precisely with the equipment I had available. I would be using a small vise, to hold the wood, a protractor to mark it, and a hand saw to make the cuts. These cuts should really be done in a wood shop where they can measure, set and cut these angles much more precisely. Therefore, I had to rely on the flexibility of the 1/8" hardboard to bend enough to offset any errors in cutting the angles.

Cutting the 52 degree angles for the frame: Infrared-Lamp Sauna
These two pieces form an angle of approximately
104 degrees, but some cutting error is visible.

Cutting the 38 degree angles for the frame: Infrared-Lamp Sauna
These 1x4's form an angle of 76 degrees.

After the boards were cut, they were screwed together with #6 x 1 3/4" flat head wood screws, and the heads were countersunk.

Attaching the ends of the 1x4's: Infrared-Lamp Sauna
The #6 x 1 3/4" screws were run
through the ends of each pair of 1x4's.

When the four boards were cut to the required lengths and angles, and screwed together; the first Trapezoid was complete. After both a top and bottom Trapezoid were assembled, they were ready to be joined together with some vertical members.

Completed Trapezoid: Infrared-Lamp Sauna
A completed Trapezoid.

From this point on, the sauna has to be assembled inside the room where it will be used, because it won't fit through any standard size door. 

The verticals serve two purposes. On one end, they form the door frame, and on the other they provide a place to anchor the three light sockets. They were attached to the Trapezoids using metal L-brackets and #8 x 1" hex-head sheet-metal screws.

L-Brackets secure verticals to the Trapezoids: Infrared-Lamp Sauna
L-brackets were used to attach
the verticals to the Trapezoids.

The first vertical for the light sockets was mounted in the middle of the 2' span. The other two members were mounted on either side of the first one, spaced so that their centers were 9 1/2" apart. This arrangement would accommodate the socket spacing in Dr. Wilson's design. With this spacing, the three verticals are so close together that one  vertical member had to be notched out to allow room for the L-bracket.

Notched verticals: Infrared-Lamp Sauna
This is how one of the side verticals was notched out
to accommodate the L-bracket for the center vertical.

The two verticals, on the other end, were positioned so that they would allow a 20-inch-wide opening in the center for easy entry into the sauna.

The Trapezoids attached with the verticals: Infrared-Lamp Sauna
The top and bottom Trapezoids with all
five verticals attached using L-brackets.