Modular Sauna Kit Assembly

Our sauna kits are built like a house! Highly insulated and stand the test of time and weather

Note: Our INDOOR and OUTDOOR modular sauna kit starts exactly the same way

The ONLY difference is an outdoor kit requires a roof. If you prefer to make your own roof, please do. Or if you ever move your indoor kit to an outdoor location, we can also sell you a sloped or gabled roof package. See open our TOC (Table of Contents) menu and click Step: Roof Installation OR view our Sauna Construction Video Series

Before You Build ...

Before you start building, you’ll need …

Good Location — A dry level surface, e.g. cement slab, tiled or wood or linoleum floor. Shims can be used to make your sauna base level
A small complement of carpenter’s power tools and hand tools and some fasteners per below
And ideally, two able-bodied sauna enthusiasts working together to lighten the load

Wall panels usually weigh 125-150 lbs, so having someone on the other end is safer and makes the project move along

Please review our videos

INDOOR / OUTDOOR KITS:

OUTDOOR KITS:

Power Tools

Air Nailer and Compressor
Cordless Hand Drill with Screw Bit Set
Chop Saw or Circular Saw
Reciprocating Sander — to smooth an accidental dent

Hand Tools

Hammer
Nail Set
Pencil
Measuring Tape
Level and square
Step stool or 4 – 6 ft ladder for roof

Fasteners +

15-18 gauge galvanized finished nails
8d galvanized finish nails
1″ deck screws for duckboard flooring OR ¹/₄″ crown staples (1″ galvanized)
2″ and 3″ deck screws*
Shims — Optional to level base plates

* T20 or T25 using 5 star bits preferred over Phillips

TIP: RELOCATING YOUR SAUNA — If you're already thinking ... one day I might move my sauna

Make relocating your sauna easier by:

Using screws wherever possible. Use an air gun ONLY to nail your trim pieces
And when nailing your corner trim pieces, only shoot one side of the wood. Then later, you can pry it off easily

Prefer to Watch a Video?

Read the Prep Work portion below and then go to:

Sauna Construction Video Series

Materials List

Unpack your Crate and Check all Materials

Lay out all materials in a dry covered location
Familiarize yourself with the sauna plan and list of materials. Please see our video regarding how to Unpack and Unload Sauna Kit upon Delivery
Lay wall panels on their side (the long edge) when storing. Do NOT put panels on end. It can damage the beveled siding

Items in your Modular Sauna Kit crate:

Interior Trim:

1×1″ corner
1×3″ door
1×2″ base / ceiling / vertical seams

Exterior Trim:

2×2″ material for corners
1×6″ material for top fascia boards
1×3″ material for bottom fascia boards
1×3″ material for door
1×2″ material for vertical seams

Optional Items, per your invoice

1×3″ material for Duckboard flooring
1×3″ material for sauna back rests and/or bench facing

✱ Occasionally your sauna heater, controls, rocks, sensor and data cable is drop-shipped separately from your sauna crate

Step 1: Secure Base Plates

Base Plate Instructions

Lay your 2×3″ base plates (BP) flat in a level space with room to maneuver
Use your level and square to check for plumb and level
Optionally use shims or measure the diagonal dimensions to make sure the base plates are square and that they are laying flat and level

For best perfect results use a level and square

Setting pencil marks on the floor as points of reference can be helpful. Check the diagonal dimensions to make sure the base plates are laying flat and level. If necessary insert shims under parts that need to be higher.

Square the Base Plates and Secure

LONG pieces always lay in FRONT and BACK positions. The short pieces go in between to make the Left and Right sides regardless if your door is on the LONG or the SHORT wall

Pre-drill and screw base plates together in corners using 3.5″ wood screws
Make sure the base plates are level and square. Use shims to level the base plates to level

Option to help keep the base plate perfectly square: Buy 4 Stainless Steel L Shaped Flat Corner Angle Bracket Plates and place on the bottom of the corners. They must be on the bottom so the wall panels sit perfectly flat

NOTE: The weight of the structure is enough to hold the sauna in place in all cases

So securing the base plates to the your hard floor is NOT necessary (unless using a floor tray for insulation). Also once your sauna room structure is set, you can still nudge the structure into place

What is a Floor Tray? We offer an interior Sauna Base Tray (or the design specs) to protect hard wood floors, to stop cold air from coming up through a deck and for better floor insulation

IMPORTANT! Keep your base plates square and level

If your base is a parallelogram (NOT square or a rectangle with perpendicular corners at 90°), then the sides are angled. This affects:

The way wall panels fit in the corners
Can rack the door. Meaning door is not plumb, i.e., one side is higher than the other changing the swing and/or proper closure

What’s in our Sauna Wall Panels?

It starts with well-insulated sauna walls: 4″ thick with layers of insulation

1×4″ T&G cedar paneling (¹¹/₁₆″) is the best material to absorb heat
Sauna Foil Vapor Barrier (¹/₆₄″) provides both reflective and conductive insulation so heat is evenly distributed over the sauna walls and immediately reflected back to the sauna interior
Walls are framed with 2×3″ cedar (2½”). Frames are studded 16″ on center
Rock wool insulation batting (mineral-based, not fiberglass) keeps heat from leaking. Note: Barrel saunas have NO INSULATION
Tar paper, a water proofing material (¹/₁₆″). An indoor sauna, of course does not require that, but it’s worth noting that our indoor modular sauna kits can be relocated outdoors – just add a roof. Our indoor/outdoor kits start exactly the same!
Beveled cedar siding (¾”). The tapered exterior siding ensures water drips away from the walls. By the way, this is a similar material to what you find in barrel saunas. And that’s all they use in a barrel sauna to contain the heat.

Step 2: Start with Wall #1

Placing wall panel #1 on the base plate

Placing Wall Panels on the Base Plate

Go to the VIDEO (part 1) of Indoor Modular Sauna Kit Assembly page

WALL PANELS vary in size but span 5 feet or less for bulk.

Panels are numbered for location and have a definite inside and outside. Tongue and Groove is on the inside. See the “What’s in our Sauna Wall Panels?” above.

TIP: IF working by yourself, use a board to pin the wall panel nearly vertical by placing it under a piece of the siding

Toe screw (at a 45 degree angle) each wall panel to the base plate nailing through panel framing member into the base plate using 3.5″ wood screws
Use 3″ wood screws to fasten sides to front and back
Screw through 2×3″ framing on corners 2′ centers (every 2 feet)

NOTE: If your sauna room is inside or in a non-windy location, you may omit nailing the wall panels as base and ceiling plates align the wall panels.

Securing Adjacent Wall #2

Secure Walls #1 and #2 to each other and the base. Use top plates to secure the top of the panels.

Once all wall panels are in place, locate your top plates (TP) and nail onto the wall panels in the same manner as the base plates

Nail top plates in four (4) places per wall panel using 2″ screws. (See Diagram 2). (Screws will remove easier if you are going to disassemble and relocate the sauna at some time

Continue clockwise making the door panel the last panel

Repeat steps above as you build the walls of the sauna room

Step 3: Secure Top of Wall Panels

Top plate secures the top of the wall panels

Similar in the way that the slot in the bottom of a wall panel is filled by the base plate, the top plate also fills and secures the wall panels at the top

Once all wall panels are in place, locate your top plates (TP) and nail onto the wall panels in the same manner as the base plates
Top plates are the 1×3″ materials that fills the slot at the top of the wall panel
Nail top plates in four (4) places per wall panel using 2″ screws. Easier if you are going to disassemble and relocate the sauna at some time

Conduit through the top plate

You’ll likely encounter a conduit coming out the top of some wall panels, especially above the heater, light, switch, etc.

While you could use a hole saw to make room for the conduit to come through the top plate. In practice, there’s no need. Simply cut off the top plate and leave a space. Later, you’ll thread conduit through holes in the ceiling panel/s.

Step 4: Set Ceiling Panels on Top

Set Ceiling Panels on Top

Locate your ceiling panels and place on top of wall panels (per your sauna plan). Review the marks on the edges indicating the front direction of the panel. Look at your ceiling panel/s. Sometimes both sides look almost the same, but one side has the sauna foil vapor barrier which belongs on the bottom (toward the sauna interior). One side is definitely smoother as well. This confirms it’s the interior of the sauna.

Secure Ceiling Panels in Place

After centering the panels, so about one half an inch extends over the beveled cedar siding. Fascia boards (1×6″) will be attached in Step 9 to the edge of the ceiling panels. Use one of the boards to check alignment of the ceiling panel.

Secure by either:

Nail ends of ceiling panels at a 45 degree angle into top plates using 16d galvanized nails OR
Screw to top plates and wall panels with 3 1/2″ wood screws. Make sure the tongue and groove of each ceiling panel lines up on the interior.

We prefer screws as you can always adjust things later, or move your sauna to another location

Step 5: Sauna Benches and Legs

Fixed Leg Bench Supports

If you opted for fixed legs under your sauna benches (the most common), please continue …

How many legs are included? We recommend and include one pre-built FIXED leg assembly for every 3 feet of bench length + 1 (only if you selected FIXED LEGs)

Sauna Benches with pre-built FIXED Legs: Installation tips:

Refer to your sauna plan for position of your benches (A, B, C, D)
Fasten leg bench supports to the walls (and other fixed leg supports) with nails or screws
From beneath the bench you can also fasten the back rails and end rails to the wall as well
The support that “floats” (i.e. where one bench meets another on the same level) can be nailed or screwed upwards through the support into the bench. You will receive (2) 2 x 2 x 24″ floor supports for each floating intersection
Cut these and use to sturdy the bench support from the wall to the bench support
When you have a HIGH and LOW bench on the same wall, you can fasten through the high bench support into the back of the LOW bench

Bench Leg profiles: FIXED Legs

Most commonly our sauna kits include fixed legs. Your package will include an array of:

HIGH Bench leg supports, 32″ high (36″ after the bench seat lays on top)
LOW Bench leg supports, 14″ high (18″ after the bench seat lays on top)

Other possible variations you may receive:

HIGH Bench leg supports recessed 2-6″
HIGH Bench leg supports with legs set back ³/₄″ to attach facing
LOW Bench leg supports with legs set back ³/₄″ to attach facing

Your like have one of these you can refer to, otherwise you ordered benches supported by ledges and operate in hot yoga saunas

Pointers when securing sauna benches with FIXED bench legs

Nail or screw supports into corners of wall using galvanized nails or coated (do not rust) 2″ screws
Place bench on top of supports and attach to wall at each end of the bench frame into the walls and through the back of the bench to the wall at panel framing members (preferred)
Put a little downward pressure on the bench before screwing into the walls so the benches are tight and do not squeak.

IMPORTANT NOTE WHEN A LOW BENCH IS RECESSED UNDER A HIGH BENCH !!

If you follow our video to the letter, you may be disappointed that the support leg occupies some surface area of the LOW bench
There’s an easy fix. Simply reverse the leg. Our video instructs you to place vertically similar to an UPPER case “P”. Reverse it to be a lowercase “b”. It will work!
However, it’s important to align the leg so you an fasten it to the strut in the bench framing. If needed, you can move the bench strut. Simple unscrew it and reattach.

HOT YOGA style bench legs

Hot Yoga style benching uses cedar ledges to support the seat / NOT pre-built legs

In this case, benches are NOT affixed at all. They float, slide and flip up to create more floor space for exercising and stretching. If you chose a 2 bench configuration, the mechanics of this are straight forward.

However IF you choose 3 or 4 benches, then the points here benches meet at a corner do create some important support problems to solve. It’s OK, carpentry solves all such problems. A quick solution is to fashion a “scarf” bracket or buy a metal plate that supports a third bench supported at a perpendicular angle (since Hot Yoga style benching has NO leg supports)

Locate studs using a nail finder
More detail TBD
More detail TBD

Step 6: Interior Trim Kit

Installing interior sauna trim

All pieces are often sent over length and need to be trimmed in the field. Trim should be installed after your sauna benches are securely in place

HORIZONTAL BASE & CEILING TRIM

1×2″ trim ( ⁹/₁₆″ x 1 ³/₈″) is provided for interior horizontal base and ceiling trim and should be installed next
Locate lengths and placement per application list. Trim will be over length for inside trimming.
Fasten trim using 8d galvanized finish nails.

INTERIOR VERTICAL CORNER TRIM

Next locate your 1″x1″ (⁹/₁₆″ x ⁹/₁₆″) for interior vertical corners
Apply per application list using 4d galvanized finish nails

Step 7: Mount Sauna Heater

Where’s my heater manual? All heaters include specific mounting and wiring instructions in their manual. Manuals are found on every heater’s page in the tabs area on our site.

Hanging Heater on Wall Panel

Extra support has been built into the wall panel for wall-mounted sauna heaters and rocks. See your sauna floor plan for your heater’s intended placement.

WALL-MOUNTED HEATERS ≤ 50LBS OF ROCKS

See the mounting instructions at right (or below on mobile device) for heaters ≤ 50lbs of rocks, refer to these and the sauna diagram for placement.

WALL-MOUNTED HEATERS > 150LBS OF ROCKS

IMPORTANT: If you ordered a HUUM Drop or Spirit with your sauna from us, then your wall panel has been reinforced to hold 150 lbs of extra weight. Please follow the heater manuals for HUUM Drop or Harvia Spirit. IF you ordered it separately (oops), then call us for extra details to best mount securely on the wall.

FREESTANDING SAUNA HEATERS

Freestanding heaters sit directly on your hard floor (wood platform, slab or tile pavers). Some heater models (Cilindro) still use a bracket secured to the wall to keep from tipping over.

EXTERNAL CONTROLS

Some sauna plans include a rough-in box for external-mounted sauna controls typically, e.g., a SC-9 or F-2T controller. The heater mounts just the same but there are additional wiring considerations for your heater operation.

Mount Sensor on the Wall

Some heaters have an internal sensor, e.g., Polar HMR series and Cilindros, so there’s nothing extra to do. Some have a capillary tube (looks like a stainless steel wire) that must be unwound and set on the nearest wall — usually best not above the heater, like the Finlandia FLB or FIN series. There are methods to concealing the wire. See the image at right.

Fine Tuning or Troubleshooting later … It’s worth mentioning that when a sauna heater does not achieve a high operating temperature (170-196°), then sometimes adjusting the sensor’s height on the wall is a simple way to affect heater performance.

Step 8: Build the Guard Rail

Requires Light Carpentry

We provide the cedar material supplies for you to build a guard rail. Depending on your site situation, the guard rail will be in the corner (2 sides) or floating (3 sides / mid-wall) or you chose a freestanding heater or an OEM guard rail or you may have opted out.

There are many ways to make a guard rail for a wall-mounted heater

For this reason, specific plans are not always helpful for your sauna situation, heater choice or placement. Here are examples of common guard rails. (Pictures sent by our customers)

FAQ: What’s actually hot on a wall-mounted heater?

Answer: These heaters are only hot on the top third. The middle third is only warm. The bottom third is actually cold.

Helpful Tips when constructing a guard rail for wall-mounted sauna heaters

Guard rails should be REMOVEABLE. Do NOT fix them permanently, as you may need to access the heater, sensor or rocks
SAFETY CLEARANCES: Guard rails can be within 2-4″ of most walls, but ALWAYS defer to the operator’s manual. You can look up your heater on our site and find it’s manual in the tabs lower down on those pages
Some prefer a wall-mounted guard rail, i.e. NO legs go to the floor. So it’s easier to run duckboard grating under the sauna heater
Some prefer the legs sit on the floor. Duckboard is cut around guard rail. Duckboard should easily be removed
Smaller saunas where the width < 4′6″ usually require a portion of the guard rail to sit on the LOW bench
Where possible, embed fasteners so you are NOT accidentally scorched

Here are the typical guidelines for SAFETY CLEARANCES for a wall-mounted heater: (ALWAYS DEFER TO YOUR HEATER’S MANUAL)

Step 9: Exterior Trim Kit

Exterior Sauna Trim / Boards

ALL pieces are often sent over length and need to be cut to size in the field

EXTERIOR FASCIA BOARD

Install the 1×6″ exterior fascia boards — ACTUAL SIZE: ⁹/₁₆″ x 5 ¹/₂″

Pick the best piece for color or appearance to go on the front of the sauna. (These are oversized, so you’ll need to cut them). You’ll affix ALL these fascia boards to the ceiling panels’ TOP edge on all sides

IF UNCLEAR, please see our video: PART III: Fastening Trim to the Sauna (0:40 mark)

First, measure the sides of the sauna (left and right of the front wall). Cut these fascia boards and affix to the top edge of the ceiling panel
Now, measure from fascia board (left wall) to fascia board (right wall) and cut the fascia board for the sauna front. This should just cover the side boards
Repeat this process for the back side

Install the exterior 1×3″ exterior fascia boards — ACTUAL SIZE: ⁹/₁₆″ x 2 ¹/₂″

The process is similar as above except the base fascia boards actually sit on level ground to start as you make the box since the beveled siding is angled

IF UNCLEAR, please see our video: PART III: Fastening Trim to the Sauna (0:60 mark)

The 1×3″ bottom fascia board will cover some of the last (bottom) piece of the bevel siding and the exposed 2×3″ base plate
Again mark where side boards meet the front board and cut
Basically, you’ll make a box around the base of the sauna securing the base boards’ ends together, then
Lift up the base board box about ¹/₂″ off the ground and secure to the sauna. This insures that only base plates are touching the actual hard floor. Any water will easily fall behind the base boards and the beveled siding

EXTERIOR CORNER TRIM

We’ve premade 2×2″ notched vertical corner trim

Apply to the exposed area at each corner of the sauna exterior
The 2×2″ corner trim is over length. Cut them to length
These will butt between the fascia boards at the base and top. Nail into place using galvanized finish nails

TIP: You only need to nail one side of the corner trim. Then if you ever relocate your sauna, these pieces can easily be pried away. If you nail both sides, it’ll crack — but you can order more from us.

EXTERIOR MID SEAM TRIM — NOT ALL SAUNA SIZES REQUIRE ONE

IF any wall of your sauna kit is over six feet, there will be a 1×2″ vertical seam trim to fill that mid-space

These will butt between the fascia boards at the base and top. Cut to length and nail into place using galvanized finish nails

EXTERIOR DOOR TRIM

Exterior door trim includes 17 lineal feet of 1×3″ materials. Provided as 3 over length pieces for the top and the sides. Some put a 10° angle on the ends of their top piece for style

Step 9: Duckboard Flooring

IMPORTANT: Duckboard Flooring is LAST item to be installed

Duckboard Flooring is NOT the hard floor of the sauna. Its a grating sitting on top of your HARD floor. Cedar is warm to the foot — much better than concrete!

Our sauna kits do NOT include a hard floor

The sauna kit will sit directly on your concrete slab, tile pavers, a wood platform typically covered with plywood, sheet vinyl or ceramic tile. NEVER carpeting or wooden paneling. We do offer a “Sauna Base Tray” (search our website)

IMPORTANT: DUCKBOARD MUST BE REMOVABLE TO CLEAN YOUR SAUNA FLOOR !!!

End view of our 1×3″ duckboard grating

BUILD YOUR DUCKBOARD GRATES:

Locate your 1×3″ duckboard grating material
The top boards should be laid face down (i.e., the surface your feet will walk on)
The runners laid on top flush with edges and 8″ apart
The top boards are nailed upside down with a ³/₈″ gap (a carpenter’s pencil) between the boards / See diagram
Nail using 1″ galvanized finish nails or 1″ staples
Duckboard should be built with the top boards parallel to the door and runners perpendicular

Step 10: Adjust Door Hinge

Adjust the self-closing door hinge

The steps to installing the self closing hinge for the sauna door

The self-closing hinge allows your sauna door to self shut, thus keeping more heat in the sauna. FYI, all sauna doors open out! This is why we only provide one door handle

Self-closing hinge for sauna door diagram

Here are the easy to follow instructions:

Basically as you rotate the nut clockwise atop the hinge you will see a hole appear; we’ll call it the “tension hole”.
Count the number of holes that pass.
On the third one, insert the tension pin into the hole and test if the door will close on its own.
If not, then let the pin stay in the hole to hold the tension. Make sure to leave enough of the pin hanging out to grab it easily.
Now, use the wrench again. Rotate the nut slightly so you can remove the pin.
Continue rotating until the fourth hole appears.
Reinsert the tension pin. Test the door again.
If it closes to your satisfaction, then you can push the pin in a bit further, else return to step 4 to continue adding more tension.

IF OUTDOOR SAUNA KIT

Step 11: Roof Installation

Roof installation requires carpentry

Sorry there’s no way around this! When installing a roof, ALWAYS have 2 workers on site. Going up and down a ladder is never effective. Roofs require someone on the ground to cut pieces, pass up supplies and keep the momentum going.

Just started these edits / MORE TO FOLLOW

Slopped Roof Installation

As of today, 11/7/2024 — please view our video Outdoor Sauna Assembly with Peaked Roof

Peake Roof Installation

As of today, 11/7/2024 — please view our video Sloped Sauna Roof Installation

Permitting: Electrical or Structural

Electric Work is Best Performed by an Electrician

Cedarbrook Sauna works with wood. We are not electricians. However, we tell you want to demand and expect below OR refer you to an electrician locally

Plenty of home owners do their own electrical work. Electrical preparation involves reviewing the electrical capacity of your service panel for available amps. For example 4×6 sauna room uses: 6kW sauna heater / 240V / 30 amp breaker / 10 gauge wire. Run electrical wire planning for the heater, lights, switch and external controls (optional).

Electric saunas require a dedicated breaker and circuit and electric work. Safety first!

Most home saunas require 4.5kW, 6kW or an 8kW sauna heater unless of course, you prefer wood-fired all-natural, then NO you wouldn’t any electricity necessarily. Though you might still want a light bulb, but lanterns work was well or the flash light on your phone. Wood-fired saunas in the city may sometimes encounter burn ban days, so consider your options.

Typically, then sauna installations will require a dedicated 240 volt, 30 or 40 amp GFI-protected circuit. If you pull an electrical permit, it covers the sauna heater, light and switch and possibly a wall-mounted control panel, etc. Commercial saunas often have two 40 amp circuits (240 V).

If you’re renovating a room and constructing a sauna in your home, and you do your own electrical permit. Then when you sell your home, you’ve covered your responsibility when you declare on Form 17 any work that was done without permits.

Structural permits are usually NOT required

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.

Sauna Care

CARE OF SAUNA ROOM

We do NOT recommend treating the interior of any NEW sauna room, especially in residential applications.

When you feel a need to clean the cedar …

Use a mild solution of gentle detergent (such as Ivory Flakes), water and a small amount of chlorine bleach as a disinfectant
Wipe wood down with this solution, then wipe down with clear water
You may lightly sand the cedar to freshen the wood
You may wish to use towels on the benches to prevent sweat stains

CARE OF HEATER

In caring for the heater, do not pour or throw “buckets” of water on the rocks. Use a full dipper or two.

Use only fresh water, no pool water, salt water, 7-up etc. Use our menthol or eucalyptus for inhalation therapy. Call for details.

WARRANTY

All sauna rooms are warranted for one year against defect in material and workmanship for residential application. Sauna heaters have a one year warrantee on the elements and a three year warrantee on all other parts.