This document discusses installing a home sauna. It begins by addressing common misconceptions about saunas, noting that unlike steam baths, saunas create very dry heat between 140-200 degrees Fahrenheit and do not pose moisture or damage risks. It then outlines different sauna installation options from prefabricated kits to custom builds. The bulk of the document provides step-by-step instructions for installing a precut sauna kit, covering framing, insulating, adding interior siding and benches, and installing the heater. Additional details are provided on traditional versus infrared heating systems and common sauna features.

1. home upgrade TE X T and photos by DAN CARY
Structures designed for people
to sit in high temperatures have
been popular throughout the world for
thousands of years. Experts may debate
the specific benefits, but many people
experience an increased feeling of well-
being from taking a sauna. (Of course,
you should always consult your doctor
first.) Having a sauna in your own home
may seem like an unattainable luxury,
but it can be a surprisingly DIY-friendly
project.
One of the biggest misconceptions
about in-home saunas is that they cre-
ate the same potential humidity-related
problems as steam baths. But saunas
and steam baths are not the same. A
steam bath or steam shower gener-
ates high temperatures (up to 110 de-
grees) and high humidity levels (often
near 100 percent), so installing a steam
room requires many construction pre-
cautions to contain the moisture and
prevent damage. Saunas create even
higher temperatures (140 to nearly 200
degrees) but low humidity (typically
less than 15 percent). Even when water
is poured on hot rocks in a traditional
sauna, the humidity level rises to only
about 30 percent for a few moments
and quickly drops back down. Because
saunas are very dry, they do not cause
moisture damage.
Another misconception is that home
saunas are too expensive and too com-
plicated for homeowners to build, but
that’s simply not the case. You don’t
even need a lot of extra space — in fact,
smaller saunas are more efficient, re-
quiring less powerful heaters and heat-
ing up more quickly.The most common
size of traditional sauna installed in a
Think installing a home sauna is too
expensive or too complicated to do
yourself? Think again. All you need
is a little bit of extra space, some
careful planning and a few common
power tools.
INDOOR
Sauna
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2. The 3 x 3-ft. footprint of this infrared unit will fit in
just about any room.
Countless upgrade options are available, including audio
systems and even televisions, but most people prefer to keep
the sauna simple. A quiet, dimly lit environment is typically best
for relaxation.
Traditional saunas feature wood walls, but you can
customize yours by incorporating other materials,
such as stone, as accents.
The Saunatonttu heater is the latest advancement in traditional
heaters. A super-insulated shell uses a small standby heater to keep
200 pounds of rocks hot and ready for a sauna with no preheating
time required.
Clamp the uprights together and cut the notches. Because
most plywood is undersize, the notches won’t be a full 3/4
in. wide. This jig (p. 34) makes repeatable notches along the
length of the uprights.
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Our custom cut sauna kit arrived in
boxes that were clearly labeled with the
contents and roughly organized in order
of installation. The kit included complete
instructions and all necessary materials,
with the exception of the framing lumber
and insulation.
Frame the walls and ceiling using
standard 16-in.-OC framing practices. You
must frame 4 x 6-in. inlet and outlet air
vents. Frame the inlet vent directly below
the heat location at floor level (pictured).
Frame the outlet in the opposite wall with
the top of the vent 23 in. above the floor.
After the wall siding is installed, the inlet
vent opening is finished with a fixed-
louvered grill (inset photo) and the outlet
vent is finished with a sliding-door valve.
Insulate the walls and ceilings. We used
R-13 unfaced insulation in the walls and
R-19 in the ceiling. You can also use
faced batts, but you must install the fac-
ing on the interior side of the framing.
Attach the foil vapor barrier to the
framing using a staple gun, overlapping
the seams by a couple of inches. Besides
serving as a vapor barrier, the foil reflects
radiant heat back into the sauna.
Traditional
vs.
Infrared
One of the first decisions you must
make when planning a sauna instal-
lation is what type of heat you want:
traditional or infrared. Traditional
heaters use heating coils that are
covered with special rocks. The heat-
er radiates warm air, which in turn
warms you. Traditional saunas allow
you to add steam to the environment
by tossing water on the hot rocks.
Infrared (also referred to as
far infrared) saunas are easily
recognized by the dark horizontal
panels that clad their interior (see top
left photo, opposite). These saunas
use infrared light rays to heat your
body without warming the air. Some
people prefer the hot environment
of a traditional sauna; other people
prefer the lower room temperature
of an infrared unit. The only way to
know what you like best is for you to
visit a sauna dealer and experience
both types of heat for yourself.
If your family can’t agree on which
type of heat is best, you don’t have to
install two saunas; the Finnleo Infra
Sauna features both types of heat in
one unit, so everybody wins.
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OPTIONSABOUNDSauna Installation
Here are just a few of the features and
design choices available today.
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3. 6
Install the bench supports. Drive 3-in.
screws through the bench supports and
into the studs. The lower bench support
runs to the back wall under the upper
bench, allowing you to slide the lower
bench back to create more open space
for easier cleaning or access to the heat-
er. In this case, the upper bench support
features a front vertical framing piece to
attach an apron.
Position the prehung door frame so
that the front edge will be flush with the
exterior siding or wall-covering material.
Drive 3-in. screws through the hinge side
of the door frame. Use shims to plumb
and level the door, and secure the rest of
the frame with 3-in. screws.
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One of the upgrades we chose for this
project was to install a backrest with a
built-in LED light strip. The strip is con-
nected to a power supply that will plug
into an outlet located in the room behind
the back wall of the sauna.
Install the interior siding, starting with the ceiling, then the back wall, then both side
walls (pictured) and finally the front wall. Start each wall with the groove edge of the
board against the adjacent wall. Use an 18-gauge brad nailer to face nail at each end
of the board (these will later be covered by corner trim) and drive nails through the
tongue at each stud. Hold the gun at an angle and drive the nails into the back edge of
the tongue so that they will be concealed by the overlapping groove of the next board.
4
5
home is roughly 5 x 7 ft., which will seat
two to four people. If your space is re-
ally limited, you can still install a one-
person, freestanding infrared sauna in
a 3 x 3-ft. space.
Planning
There are several approaches to
building a sauna in your home. The
fastest and easiest DIY option is to
purchase a prefabricated kit that
includes factory-built walls and ceiling
panels. All you have to do is connect
the panels (or easier yet, hire the sauna
dealer to assemble them for you).
These kits can be assembled and fully
functional in just a few hours.
The other end of the construction
spectrum is to build the sauna from
scratch. This will require a lot more
time and research, but it allows you
the freedom for complete customiza-
tion, and it can also be much more eco-
nomical if you’re thrifty when buying
materials.
The happy medium between
prefabricated and built-from-scratch is
to purchase a precut kit from a sauna
manufacturer. I recently installed a
precut kit manufactured by Finnleo
Sauna (see sources), based in Cokato,
Minnesota. I submitted detailed
measurements of the space, and the
company provided a construction
drawing for my approval. Once the
drawing is approved, it typically takes
a few weeks for the company to cut
and ship the tongue-and-groove siding,
benches, door and windows.The heater
and control panel are also included
with the kit. I was responsible for the
framing materials and insulation.
Installing a precut kit is a project that
can be completed by an experienced
DIYer in a weekend. The only power
tools necessary are a miter saw, a
jigsaw, a drill/driver, an 18-gauge brad
nailer and a compressor. (You could also
hand nail the siding boards.)
Ideally, a sauna should be installed
near a shower so that you can rinse off
immediately afterward. If you’re not
lucky enough to have 35 sq. ft. of extra
space in one of your bathrooms (and
few people are), the next best option
Sauna Installation
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4. The Essential Sauna
By Gary Legwold
It’s a cold, blustery, pile-on-the-layers
day that has designs on dragging me into
depression. But my defense is my 4 x 6-ft.
basement sauna, which I just turned on.
As this electric sauna warms to
between 180 and 210 degrees F, I want
the day to get worse. Bring it on — all
the foul weather you can muster! I won’t
cower; I’ll stand naked and thumb my
nose at it, knowing that I’m steps away
from being cozy in my dark, double-
bench cocoon, sweating away all gloom
and singing life’s praises.
The sauna tour
When I assembled my sauna from a kit
years ago, I at first considered this a
luxury project inspired by a three-city
(Turku, Tampere and Helsinki, Finland)
sauna tour I took. Tough assignment,
but I gutted out the daily grind of testing
saunas and eating well.
The tour ended at the 4,200-member
Finnish Sauna Society in Helsinki. The
facility includes five saunas heated with
firewood and three savusaunas, “smoke
saunas” with chimneys. Typically, you
start in a mild sauna, progress to hot and
then finish with a savusauna, which has an
intense but very smooth heat.
After each sauna, you go to a porch
leading to a hole in the ice covering the
Helsinki Bay. You can jump in, walk a
slow death downstairs into the water or
pass and enjoy the experience of being
naked outside in winter and yet feeling
absolutely comfortable and at peace.
Following the saunas, you shower and go
to a cafeteria, where you are served beer,
coffee or tea with sausages and mustard.
Your day is pretty much done after that.
A sauna is not a luxury, in my book. It’s
essential for mental, physical and even
spiritual health. We are DIYers because
we do projects to make our living spaces
better — our kitchens, bathrooms,
garages, etc. A sauna project will make
living better. On bad days and good, a
sauna will slow you down and pick you up.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gary Legwold is a writer and home improver
based in Minneapolis, where more snow
means more saunas.
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Mount the heater to the wall. We used
the manufacturer-supplied template to
mark the locations of the lag screws
that will support the mounting brackets
(inset). Loosely surround and cover the
heater coils with the rocks provided by
the manufacturer.
Connect the control pad to the temp-
erature sensor and heater. This control
pad features a touch screen and is con-
nected to the heater with a CAT5 cable.
is often in an unfinished corner of the
basement. Even the empty space under
a stairway is often sufficient for a one-
or two-person sauna.
Most traditional saunas require a
240-volt circuit to power the heater as
well as a 120-volt circuit for any lights
or other electronic accessories. Check
the manual of the heater you select for
specific power-supply requirements.
All electrical work should be done and
inspected by approved professionals.
Materials and construction
A sauna is simply an insulated box with
a door. Frame the walls and ceiling with
2x4 lumber, following standard 16-in.-
OC framing practices. It is important to
frame openings for a 4 x 6-in. air inlet
(see photo 1, p. 28) and a similar-size
air outlet to provide fresh-air exchange.
The inlet is typically located at the base
of the wall directly under the heater,
and the outlet should be installed
approximately 24 in. above the floor in
the wall opposite the inlet.
Wood is the only material recom-
mended for the interior siding, but it
is acceptable and increasingly popular
to use other materials, such as stone or
glass block, in small areas as accents.
Softwood species are the ideal material
for the interior because they do not
get as hot to the touch as hardwood.
Avoid stock with large knots, which
do get very hot to the touch, or stock
with visible sap, which will run when
it is heated. Cedar, hemlock and poplar
are popular options in North America;
Nordic white spruce remains the
preferred choice in Scandinavia.
You can clad the exterior with
whatever material you like. The most
popular choice is to use the same or
similar wood siding that was used for
the interior to maintain a traditional
sauna appearance. Another option is to
use a material (typically drywall) that
blends in with the surrounding walls.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dan Cary is an experienced woodworker,
an avid DIYer and a knowledgeable home-
improvement writer.
SOURCES
Finnleo, finnleo.com
Installation
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