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How to Build a Sauna: Crafting Tongue-and-Groove Walls and Ceiling in a Sauna

Licensed contractor Paul Ryan shows how to build a custom sauna from a pre-cut kit. Tongue-and-groove walls and ceiling are installed as part of the finishing.

More in Bathroom

basement becomes fitness area with sauna from kit
  • Time

    Several Weekends

  • Price Range

    $2,500 - $5,000

  • Difficulty



Step 1: Apply the Insulation

Using a hammer tacker or a staple gun, attach the foil vapor barrier, which is supplied with the sauna kit, to the walls. Starting at the bottom, work your way up with about a 5" overlap and finally up over the ceiling joists. The foil helps keeps the heat in and moisture out of walls.

Note: It's important to use unbacked insulation underneath the sauna walls on the wall base so you don't create a double barrier which can trap moisture when you apply the foil barrier. Be sure to cut away any existing vapor barrier in the space you are building the sauna.

Step 2: Install the Tongue-and-Groove Ceiling

Using a pin nailer, start installing the ceiling boards with the tongue against the wall. The ceiling goes up first so the boards will be supported at their ends.

Face nail through the board on each end staying far enough away as to not split the wood. These nail heads will later be covered by trim. Note: Face nailing sends the nail perpendicular into the wood with the nail head exposed.

At roughly a 45 degree angle, blind nail the remaining boards into the joists through the tongue. Note: Blind nailing forces nails into the grooves of the tongue-and-groove boards.

The ceiling will require the most cutting where your board ends meet the walls at an angle. With a sliding T- bevel, measure the angle for your end cuts and transfer that angle to your miter saw.

install tongue and groove ceiling

Step 3: Install the Tongue-and-Groove Wall

On each wall, the first board should be fastened with the tongue toward the corner in the same manner as the ceiling.

Like the ceiling, continue the process until the walls are up. Make sure the tongues and grooves are snug.

In the next phase of the project, we finish the wall, install the heater, benches, doors and windows.

install tongue and groove wall

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