7 Simple Steps to Build a Sauna in a Garage

If you love relaxing in a sauna, you might be thinking about installing one at home. But what do you do if indoor space is tight?

Well, one option is to utilize a garage. It has the advantage of being close to the house and more sheltered than the garden. And with some guidance, building a sauna here can be easy enough to do.

That’s where we come in! We’re going to walk you step by step through how to build a sauna in a garage. So if you’re thinking about giving it a go, just read on …

Build Sauna in a Garage

Tools and equipment

  • Tape measure
  • Spirit level
  • 5-inch plywood
  • 2 by 4 planks
  • Saw
  • Your choice of insulation – fiberglass, thermal barrier or wool
  • Stapler
  • Nail gun or hammer and nails
  • Screws
  • Electric screwdriver
  • Cedar planks with tongue and groove edges
  • 2 by 4 flat cedar planks
  • Mounting brackets (optional)
  • Your choice of lighting
  • Your choice of flooring
  • Sauna heater

Step-by-step guide for DIY Sauna in a Garage

DIY Sauna in a Garage

Step 1: Plan your sauna

There are lots of options when it comes to building your own sauna. To begin with, decide how much work you’re prepared to do.

We’re going to give you an overview of building your own sauna from scratch. But if you want to keep things simple, you can buy a ready-made sauna in kit form. You’ll still need to do some preparation, though, to make sure the location is suitable.

Measure the space and decide how large you want your sauna to be. Chalking out the area on the floor of your garage can help you get a feel for the space.

If you’re using a kit, you’ll also need to check that the garage floor is level. Use a spirit level to do this, and remember to check in a number of different directions. If the floor isn’t level, sand down any lumps and fill any hollows before beginning installation.

Check the location of any existing power lines in your garage. If possible, position your sauna near existing wiring to give yourself less work to do.

Think about ventilation too. Including pipes to vent air in and out will make the sauna more comfortable.

If you’re going to build your sauna from scratch, now is the time to make a detailed plan. Record all the dimensions and note where you’ll put power lines, ventilation ducts, lighting, the sauna heater and the door.

Speaking of the door, decide whether you’ll make your own, or purchase one ready-made.

Pro tip: If you’re building a sauna from scratch, it’s a good idea to locate it in the corner of your garage. That will allow you to use two of the garage walls as part of the structure.

Step 2: Bring together your materials

If you’re putting together a sauna kit, you’re now ready to get started. Read through the instructions carefully first, and make sure you have all the tools you’ll need to hand. There’s nothing more annoying than having to interrupt your build because your electric screwdriver isn’t charged!

If you’re building your own sauna, though, it’s now time to put all the measurements you’ve made to good use.

The first part of the structure you’ll build will be a frame for your sauna. Use the measurements in your plan to decide how many pieces of 2 by 4 you’ll need, and how long they’ll need to be.

Plan your frame with the vertical planks the same width apart as the width of your insulation. That will allow you to put the insulation in place without having to trim it. Remember to leave a space for your door, and any window you want to include.

You can also use your plan to determine how much insulation you’ll need. Multiply the width by the length of each wall to get the surface area you’ll need to cover.

It is possible to build a very simple sauna without any insulation at all. This YouTube video shows a basic build being completed in just three hours! But if you’re looking for a more comfortable and energy efficient option, it pays to spend time on proper insulation.

Pro tip: Your sauna will be much more efficient if you insulate the ceiling too. Don’t forget to add in its surface area when calculating how much insulation you’ll need.

Step 3: Build the frame for your sauna

Use your planks of 2 by 4 to build the sauna frame. Then attach your plywood to the back so that it covers the whole area.

Leave a space of 4 inches between the garage walls and the exterior wall of the sauna. And leave the same distance between the garage floor and the bottom of the sauna door.

You can either nail or screw the frame together, as you prefer. If you have one, a nail gun will make the job easy.

With the frame in place, you can now install the wiring for the heater. This is also the time to add the pipes for ventilation, and the wiring for your lighting.

Pro tip: The frame will be large and cumbersome. It’s easiest to build it on the floor, and then move it into position. Work on one wall at a time before nailing or screwing it into place.

Step 4: Insulate the walls

Now that the frame is in place, you’re ready to add insulation.

You have a number of options when it comes to the material for this. Wool is a great eco-friendly insulator, and it’s very effective. If you can, buy it in panels rather than rolls. These are sturdy enough to prop them up inside your frame. Then just staple them in place.

Alternatively, you could use a mixture of fiberglass and thermal barrier. Thermal barrier is the stuff that looks like bubble wrap covered in metallic foil.

Both options are light and easy to work with. Roll the fiberglass into position first, nearest the exterior of your sauna. Then secure it using a staple gun. Now add the thermal barrier on top, and staple it in place.

You’re now ready to start cladding your walls with wood.

Step 5: Clad the walls with cedar

This is the point at which your structure really starts looking like a sauna!

Take your lengths of tongue and groove cedar and nail them into place on your walls. You can have the planks running either vertically or horizontally, as you prefer. Most saunas, though, have them running horizontally.

Ideally, you want a single plank to cover the whole width (or length) of the wall. The wood will expand and contract as the temperature in the sauna changes. Using a single plank will mean you won’t have to worry about gaps between the wood.

Choosing nails with small heads will give you a neater finish. And if you want to avoid seeing nails at all, you can choose mounting brackets. These slip over the tongue of the wood and have a hole for the nail. When the next piece of wood is added, the nail is completely hidden.

Pro tip: Make sure you choose wood with a long tongue – that’s the lip along the edge. That will ensure the wood still covers the insulation, even when it contracts as the sauna cools.

Step 6: Build your benches and door

Build your benches and door

Now that the shell of your sauna is ready, you can start putting the other elements in place.

Building your own benches is easy to do and means you can get the perfect fit.

Sandwich four pieces of 2 by 4 cedar between two more pieces to make the seat. The four in the middle should lie flat, while the pieces on either side should be turned on their ends. Add one more piece at right angles across the bottom in the middle of the seat. That will provide extra support.

Now use other pieces of 2 by 4 to make the legs. You want your bench to stand about 20 inches above the floor.

If you’re going to build your own door, now is the time to do that. Alternatively, there are lots of good ready-made doors available at very reasonable prices.

Pro tip: Adding a second bench at a higher level will give users a choice of temperature zones inside the sauna.  Place the two benches next to each other so the lower one can act as a step to the upper.

Step 7: Add the other fittings

Now wire in your sauna heater and lighting. Don’t try to use an ordinary heater in a sauna – the temperature won’t get high enough.

You’ll also need to ensure your heater has the right power output for the space. To do that, multiply the height of the sauna in meters by its length and height. Then add one for every door and window. The answer will give you the kilowatt rating for your ideal sauna heater.

Last but not least, fit your flooring and door. You’re now ready to enjoy your very own home sauna!

Are you inspired to give it a go?

We hope you’ve enjoyed our step-by-step guide to how to build a sauna in a garage!

If you want an easier build, a complete sauna kit or a ready-made sauna door and benches are good options. But with careful planning, there’s no reason you can’t make the whole thing from scratch. And it will be considerably cheaper too.

Enjoy your project – and we hope you’re soon relaxing in your garage sauna!

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Build Sauna in a Garage