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DIY How To Build A Sauna FAQs

DIY: How To Build

How high are the standard sauna benches?

Sauna bench dimensions

In our modular sauna kits, we build our lower benches at 18" high and the upper benches are 36"

Of course, we're happy to alter this as you need at no additional cost. You'll find some sauna benches here if you want to order them separately.

We can make them as wide and as long as you'd like. All our sauna benches are made to order, at no extra charge except for the wood. Typically we quote benches as 18" wide at $40/ft.

Our sauna benches features:

  • All benches are screwed from the bottom so there are no exposed fasteners, so you can NOT get burned
  • All clear western red cedar lumber
  • Pre-built bench leg assemblies included – one for every three foot of bench
  • Standard tops are 1½" wide (2x2), but other widths are available.
  • Benches are usually 18-22" wide; a double-wide bench is about 40" wide.
  • Lower benches at 18" high and the upper benches are 36".

We're happy to answer other questions. Thanks.

Can I use a wooden base for the prefab sauna kit?

We set a pressure treated wooden base with a plywood overlay

Setting your wooden base for your outdoor saunaWooden sauna base for outdoor home sauna kit

In our case, we were making the video and wanted to show you from start to finish how to erect the prefab modular sauna. Many customers who purchase an outdoor sauna set them on a cement slab, pavers, tile, or a deck, or other.

A wooden base has the advantage of making relocating your sauna later to another location much easier. Wood will rot if in contact with wet dirt, so use pressure-treated wood as your sauna's base, or use something more permanent. Then ...

Cover your pressure-treated wooden base with a vapor barrier and plywood

After completing the wooden base, staple some 6mm plastic over the top. This acts as a vapor barrier and protects your sauna's sub flooring from moisture. The plastic is then covered by two sheets of plywood (at least ½" CDX). If desired, you could cover the plywood with hardy board and tile. Or later, you can cover the plywood with removable duckboard cedar flooring.

Also noteworthy, IF you live in an area where ants are prevalent, you might consider putting diatomaceous earth under the plywood as pest control. This is one of the few natural remedies which make ants turn around fast. Diatomaceous earth will cut into an ant's exoskeleton, so they avoid it entirely. Caution: Do NOT breath diatomaceous earth. It is an extremely fine dust and can agitate your lungs. Always follow the manufacturer's label during application.

How should I add my cedar paneling to the sauna ceiling and walls?

How to Build a Sauna: Adding tongue and groove cedar paneling

Begin on one side of your ceiling and nail your cedar panel boards perpendicular to the joists. Move across the ceiling until covered. As needed, cut a hole around the light box. Best if your light and switch are wet-rated.

Adding cedar paneling to the sauna wallsNext, nail the clear cedar paneling boards over the insulation and foil barrier. Nail your first row of tongue and groove wall boards to your studs horizontally, tongue up, groove down. Start from the bottom and move up. Generally, you only need nail the tongue after fitting it snugly over the prior row. This way the nail is hidden by the groove covering it. Vertical paneling is possible, but requires either plywood sheeting over the studs or some strategically spaced horizontal studs over the vertical studs.

Add your cedar panel boards in rows, checking for level every 4th board or so. Fit the grooves over the tongues and continue up the wall. Along the way, you may need to cut for electrical junction boxes for lights, switches, etc. That's the beauty of cedar, it's soft to work with and cuts easily. Continue installing your panel boards until your insulated walls are covered. At the last row butting the ceiling, remember you need not be perfect. If you're within a quarter inch you're fine. The trim pieces will cover any gaps.

See our videos and article here: How to Build a Sauna | Converting a Room to a Sauna

How do I install an electric sauna heater?

Installing an electric sauna heater

This question is answered in ouir Sauna Heaters FAQ area: See How to install a sauna heater?

How do you apply sauna foil vapor barrier?

Tips when applying your sauna vapor barrier to your sauna

A sauna vapor barrier is very important and a step that should never be skipped

Installing sauna foil barrier
  • A sauna vapor barrier is very important and a step that should never be skipped and do NOT use a substitute — it could melt at sauna temperatures. The foil will never melt and is odorless.
  • See our installation step: How to Build a Sauna: Foil to Reflect the Heat for installation tips. See our list of sauna foil sizes.
  • It's worth noting that the sauna foil vapor barrier adds a R-1 value to your insulation factor, and acts as a vapor barrier, protecting your wood

The techniques we follow are:

  • Start with the ceiling then the walls.
  • Staple the foil vapor barrier to all interior surfaces; the wall and ceiling, not the floor. Overlap your wall foil over the 3" of the ceiling, helping to keep rising heat near the ceiling.

Sauna Foil Vapor Barrier sizes

A vapor barrier protects your walls from absorbing vapor. Some steam in your sauna is great to help bring on a sweat, but it creates humidity that should not seep into the walls. Venting a sauna into your house is fine.

Select the sauna foil size that fits your sauna.

To best answer, you may want to see: How are home sauna kits built? | Explain Precut vs Prefab.

Also we provide these sauna How-To articles plus a comparison of ALL the most common sauna kit options: 

How to install a sauna door?

Hanging your sauna door in your sauna

installing a sauna doorWe have a great article and video demonstrating how to install a pre-built pre-hung cedar sauna door.

It's always better to install a prehung sauna door. These come with a frame and the swing is already set.

We build cedar sauna doors with windows of all sizes, and etched glass:


Do I need an electrical permit for my sauna?

Electrical permit for the home sauna

Wiring coming into the sauna for the sauna heaterMost sauna installations will require a dedicated 240 volt 40 amp GFCI protected circuit. If you are adding your sauna to a spa, clinic or military base, you would definitely want an electrical permit for your sauna. Commercial sauna often have 2 240v 40amp circuits.

If you are doing remodeling construction on your home it's never a bad idea to pay for an electrial permit. Then, when you sell your home you've covered your bases. Of course, many home owners simply declare on their Form 17 any work that was done without permits.

Additionally, home saunas generally do NOT require a structural permit.

What insulation should be used in a home sauna?

Insulation for your home sauna

Indoor saunas with 2"x4" studs do just fine with R13 insulation. Any exterior walls with 2"x6" studs should still have R19 insulation. Ceiling insulation should be R26 or greater.

Also VERY IMPORTANT, and a step never to be skipped is covering your studs with the Sauna Foil Vapor Barrior. It reflects heat back into the sauna and keeps moisture from seaping behind your cedar.

By the way, the prefab home sauna kits we sell come pre-insulated.

What are my base options for my outdoor modular sauna kit?

Prepare the base for my outdoor modular sauna kit

Wooden sauna base for outdoor home sauna kitIMPORTANT: First note that the exterior size of our prefab modular saunas is 8" wider and deeper than the size in the title. For example, a 5'x7' outdoor home sauna kit (the title reads 5'x7') has an exterior measurement of 5'8' x 7'8" — thus, this is the minimum size of your sauna base.

In the pic at right, we used pressure-treated wood to start our outdoor sauna base. We did this mostly to expedite our video and it was easy to take down after, and makes sense if you know you will relocate your sauna. This base is still a fine choice for your application. You may want a better floor than plywood though.

The outdoor modular sauna kit will sit well on any of these bases:

  • Pour a concrete slab. Leave concrete surface bare or lay tile over the top.
  • Tamp down gravel and lay patio pavers over.
  • Gravel with pressure treated wood works well also. In fact, if you know you will be relocating your sauna, it's even easier to bring your base with you. See step 1 of our How to Build a Sauna | Setting up the DIY Prefab Modular Sauna Kit.
  • Build a wood deck and install marine plywood on your joists, and then put tile or sheet vinyl on the plywood for a vapor proof surface.

What nails should I use for tongue and groove panel boards?

Best nails for securing the interior of your sauna

Use 1¼ galvanized finished nails.

Hopefully you have a nail gun. If not borrow, rent or buy one. You can often buy the whole set up at home depot for around $240 or may get lucky on CraigsList. You could hand nail but that would take the fun out of it .. enjoying your sauna!

Also see our article on How to Take a Sauna.

What type of circuit breaker should be used in a home sauna?

Circuit breaker for a home sauna

Wiring in a home saunaWe recommend a 240 volt 40 amp circuit breaker in nearly all home sauna installations. Of course, the sauna heater's manufacturer's spec should be adhered to as well as consult your local union electrician and permitting code for your situation. Commercial saunas may require two 240 volt 40 amp circuit breakers.

Are there saunas I can just plug-in or use on standard 120 volt power supply (as is standard in most homes except for the dryer and the stove)?

Yes, see these sauna choices:

Should I insulate the concrete floor in the traditional dry sauna?

Sauna flooring and insulation

Since sauna bathers sit on benches and heat rises, insulating your sauna floor is not necessary. This is very little heat loss because of a cool floor. In fact the sauna heaters are made to draw cool air and heat it. Then sauna bathers can vent the air out using the sauna vent slider when it's too hot, or just keep circulating fresh air.

Sauna air flows best with cool area coming in at the bottom and some hot sauna air leaving at the top. This ensures proper air flow and fresh oxygen to the sauna bathers. Generally, there is no significant heat loss through the floor.

What should I cover my sauna floor with?

Sauna flooring options

Sauna cedar flooringSauna Rubber Flooring SquareWe prefer to walk on cedar sauna duckboard or grated flooring in our saunas. Cedar is soft to the feet, but not cold. Concrete or tile sauna floors feel very cool after taking a sauna. Also our duckboard kits are built in 18"x48" rectangles that are easily removable for washing or sweeping.

Also take a look at the Sauna Rubber Flooring Squares, an interlocking rubber floor tile for the sauna or steam rooms to help you keep your footing.

What kind of subfloor is appropriate for a traditional sauna?

Sauna Floor Choices

Most outdoor saunas are set on a concrete slab, pavers, tile, or a deck, or plywood over pressure-treated wood. A wood base does make relocating your sauna to another location much easier.

Indoor sauna are built on concrete, tile, vinyls, or any non-permeable surface, ie, anything that will not absorb water. While obvious to us, it deserves to said, "never put a sauna on carpet."

Should I enclose the space under the sauna benches to make the sauna easier to heat?

Enclosing your sauna bench is not necessary and best to leave accessible

Sauna bench facingWe DO like the style and functionality of adding bench facing to our sauna benches. It's a style choice that complements in these ways:

  • The sauna bench facing hides the space in the back of the sauna, and
  • Gives the lower bench sauna bathers a useful back rest, and
  • When lighted offers a wonderful soft ambiance from underneath.

The bench facing does not enclose the air space though.

What's the best ceiling height for saunas?

Sauna ceiling height

We recommend between 6'4" and 7'. A shorter ceiling means your sauna heating costs are lower. Of course, consult the manufacturer's specs for your sauna heater, but generally most sauna heaters are engineered for ceilings no higher than 8'. Ceilings higher than this might adversely affect the sauna heater's sensors, thus overworking the sauna heater. The adage "form follows function" very much applies in the realm of sauna construction.

Do I need a structural permit for my sauna?

Structural permit for the home sauna

Commonly, an outdoor sauna and structures of 120 sq ft or less do not require permits (in the U.S.). Some counties allow larger structures of up to 200 sq. ft. without permits. You may run into some problems if you put your sauna right on the property line you share with a neighbor, a parking strip or an access easement.

While adding a residential circuit is fairly straight-forward for any electrician, it may not be a bad idea to get an electrical permit for your indoor sauna. You can call your county permitting department to easily check. Most sauna installations require 220/240v power with a hard wire connection to a separate 30 or 40 amp breaker in your electrical panel. In some instances, a small tradional style sauna can be wired to 110/120v circuit, if the circuit to the panel with a #12 gauge wire.

You will definitely want an electrical permit for your commercial sauna.

How should I vent my indoor sauna?

Venting your indoor sauna | We get these questions alot:

  • Can I vent my sauna heat back into my house?
  • Or do I have to vent the sauna to the outside?

Cedar Sauna Vent SliderIt is best to vent the sauna back inside the house rather than to the outdoors. The main reason is that the barometric pressure outside is often different than indoors and this can create reverse flow bringing air from the outside in. Also, you always want to minimize penetrations to the outdoors. Though it might seem like a great way to add heat to your house, but a sauna will add very little positive heat to your home as by design; it is meant to heat a small enclosed space. Also FYI, the sauna will not add any significant moisture to the adjoining air space. Even when you ladle water over the sauna heater rocks you add very little actual humidity to the air. Saunas provide very dry air. The humidity of a sauna ranges from 10-35%.

Sauna Vent GrillMost importantly, the air coming into the sauna through the intake opening should be fresh and cooler than the heated sauna air. Fresh air also affects the sauna heater's thermostat and hi limit sensors. Otherwise, the sauna heater may sense that the room is prematurely hot and thus shut the heater down before the desired temperature is reached. Also the fresh air air will have slightly higher oxygen levels but do not be concerned with oxygen levels as the sauna rooms are no where near near air tight. Many saunas do just fine with a wide crack at the bottom of the door serving as the intake vent.

See more information relating to this subject under our accessories: sauna vents and grills. Also see our full article on this topic: Sauna Venting and Framing Info. Vents and grills do not include hardware as customers have different size nail guns or preferences on screws. We use 1 ½” galvanized (or stainless) finish nails.

Will you just sell me the lumber for my sauna?

Cedabrook will sell you cedar lumber for any sauna, home improvement or garden project

So yes, if you're looking to buy the lumber yourself and make all your own cuts. That's great. We like doing that ourselves, too. We offer lumber for saunas, raised garden beds, doghouses, gazebos, sheds, split fencing, arbors, and more!

We offer and quote for our customers SMPs (Sauna Materials Packages) in the form of precut saunas for homes, gyms and spas. There is no additional cost to precut the lumber for your framed room, but we are happy to sell you just the lumber.

We've been making a host of products from cedar for 40 years.


If you don't see it, give us a call … on the phone, the greatest invention since the internet! 1.800.426.3929

How can I save the most on my sauna?

Save when building your own sauna!

We understand, when building your own sauna sometimes you need to do it as cheaply as possible.

  • Save time. Complete your spare room with a precut home sauna kit.
  • Build your own benches. We can provide the wood and instructions.
  • Use 1x material for your bench tops. Using residential 9/16" sauna bench tops instead of the commercial 1½" (2x2) saves and works well.
  • Two-piece wall construction. You sacrifice that nice clean look of a sauna wall without any gaps, but the savings are huge when using 2 pieces to span your studs vs longer 4', 6', or 8' T'n'G cedar. Thus, an 8' wall would spanned by 2 4' pieces, a 6' wall spanned by 2 3' pieces. Save even more using finger-joined cedar material — very green and a fantastic use of very short pieces.
  • Fit your sauna with only two benches. Some saunas seem cluttered with 3 or 4 benches.
  • Vent your sauna from under your door. Thus, sparing you the time and expense of a lower vent. You will still want to keep the upper vent though.
  • Pull your own wire. Work closely with your electrician and pull your own wire. Save the critical connections for the expert.
  • No frills sauna door. Order a sauna door made with tight knot cedar (no window). These are still great sauna doors, and the knots add a Ponderosa style. Choose your cladding width and direction.

I'm converting a room in my house to a sauna, do you have any supporting articles to get me started?

Converting a room in my house to a sauna support articles and videos

Yes, since building saunas for 40 years, we've accumulated a bit of knowledge. See our list below:

I'm just starting to plan my sauna. Are there any sauna floor plans or guidelines?

Yes, see the help pages:

And watch our "How to Build a Sauna" videos at:

  • How to Build a Sauna | Converting a Room to a Sauna — This informational article and videos demonstrate how to tack up your sauna foil, attach cedar paneling to the interior of your studs, mount your sauna heater, install your sauna benches, hang your sauna door, and finish trim and entry walkway.
  • See our list of How to Videos.

Other important sauna considerations are:

  • Type of sauna heater (gas, electrical, wood, infrared)
  • How many sauna bathers will use the sauna at once
  • Sauna room size to determine how powerful your sauna heater must be, and last
  • Where to put the heater, bench arrangement and venting for your layout