How To Build An Outdoor Sauna

So you fancy having a sauna? Not a bad idea, all things considered. There’s nothing like a sauna for detoxification through sweating, improved circulation, enhanced muscle recovery, and stress relief. [1]

But there are a few considerations you need to know about before getting started. If you’re going to build the sauna yourself, you’ll need a proper plan (see our step-by-step guide). If you’re not that handy, you could also look into buying a prefabricated sauna, which will be easier and a great deal faster. 

If you want to build your own sauna, then keep reading. But if you’d rather just get on and buy a sauna, skip to the end of the article where we explore some options. 

Building codes and regulations

Unlike Finnish saunas that are highly regulated, we British do not have strict building codes for sauna building. This has its pros and cons. The pros are that you can buy outdoor sauna kits and erect them fairly cheaply, speeding up your outdoor sauna build. The cons of this are that you end up having foundation, drainage, insulation, and vapor problems without proper guidelines. 

It is advisable to check with your local council or access documents such as Approved Document G and other documents to keep you on the right path. If you’re unable to build outdoors, an indoor sauna is also a feasible option if you have an extra room or extension. 

Different types of saunas

Begin your planning by deciding what type of sauna you would like. This is the starting point because it will influence all your other decisions. Here are three of the most popular types:

• Traditional Finnish Sauna: Uses a wood-burning or electric heater with heated stones to produce steam when water is poured over them. The sauna operates at temperatures of 70-100°C (158-212°F).
• Infrared Sauna: Uses infrared heaters to directly warm the body without heating the air as much, typically operating at temperatures between 40-60°C (104-140°F).
• Steam sauna (wet sauna): Similar to a traditional sauna but with higher humidity levels.
• Prefabricated sauna: This is the most common type of sauna found in the UK because it is easy to install and maintain. Pod-shaped saunas provide the ideal solution in small garden spaces and backyards. 

Palmako Timber Oval Sauna - 3mx2.7m

Location selection

Once you have decided on the type of sauna you want, you can turn your attention to the sauna’s location. Choose your location based on the following criteria:

• An outdoor space that will allow you to lay a solid foundation.
• Choose enough space to allow proper ventilation and the installation of electrical components (mainly for electric and gas saunas).
• The spot should be private and away from public sight.
• The sauna must be far enough away from pools, ponds, installations, and building structures that make it difficult and unsafe to access.
• The ideal place should be shielded from the wind, as this will help to maintain the temperature.

Firm foundation

In the UK, there are three common foundation types you can use, namely:

1. Gravel and paver base
2. Timber frame or decking base
3. Concrete base

Gravel foundation

This is a cost-effective option which is also good for drainage and used mainly for smaller or prefabricated saunas. It involves compacted gravel topped with paving stones, ensuring proper drainage and preventing moisture buildup.

Wood frame foundation

A wooden frame is suitable for lightweight, wooden structures. The most versatile of the three options, it is easy to take down when you decide to move or if sauna life has lost its appeal. This type of foundation allows for natural airflow under the sauna and therefore prevents rot or water damage. However, the timber frame or decking should be treated to prevent insect infestations.

Concrete foundation

A concrete slab is possibly the trickiest of the three types for DIY projects. The time and effort it takes to lay a concrete base can also be a deterrent as it requires knowledge of how to mix concrete, pour it, lay redbar (if necessary), and use a compactor. 

Structure construction

The use of moisture-resistant building materials is a must for a DIY outdoor sauna. Use woods such as Nordic spruce, cedar, or hemlock for the walls and interior benches. Additionally, pay special attention to insulation and vapour sealing. 

Sauna insulation

Proper insulation is important for two reasons: It helps your sauna heat up efficiently and guards the surrounding structure from excessive heat exposure. When building your own outdoor sauna, two approaches are usually applied:

• Rockwool and aluminium sheeting: This method is becoming increasingly outdated because standard construction aluminium is not constructed to withstand extreme temperatures, and Rockwool insulation can leave gaps within the stud framework, causing cold spots to develop.
• Foil-back insulation board: A more modern and alternative approach when building your own sauna is the use of an insulation board that can withstand sauna temperatures without degrading and that prevents thermal bridging, ensuring even heat distribution. 

Vapour barrier

The UK does not have any regulations regarding the sealing of saunas like they do in Finland. However, vapour sealing is the primary barrier that stands between wet, warm air escaping and damaging the underlying wood framework, which will then develop mold, mildew, and rot. Therefore, this is not a step you should skip when building your sauna room, as mold and mildew damage can be very expensive to fix. 

Use an aluminum foil vapor barrier with paper backing as it can withstand high temperatures without melting or off-gassing (the release of volatile organic compounds (VOCs), which are harmful chemicals like glues, stains, and plastics used in the construction of the sauna).

Ventilation

An outdoor sauna still needs ventilation as it ensures continuous fresh air circulation, prevents overheating, and helps remove excess moisture. Without adequate airflow, saunas can become humid, stale, and prone to mold buildup.

Heater installation

Now that you’re pretty far down the line with your project and looking forward to your sauna sessions, it’s time to focus on the sauna stove. Here are your options for stoves.

Sauna interior

When designing the interior of your sauna, you should think along the lines of practicality meets comfort, meets style. The use of high-quality, heat-resistant wood for the sauna floor, paneling and benches is a must, but you should also consider these additional elements:

• Incorporate multi-level benches to allow users to choose their preferred heat intensity.
• Install soft, warm LED lighting to create a relaxing atmosphere.
• Ensure proper placement of air inlets and exhaust vents to maintain fresh airflow.
• Add thermometers and hygrometers to monitor temperature and humidity.
• Incorporate aromatherapy options, such as essential oil dispensers or sauna herbs.
• Use a tempered glass sauna door or a solid wooden door ,which are excellent for heat retention. 

Step-by-step construction process

Once you’ve thoroughly considered and planned all your sauna elements, it’s time to begin the basic step-by-step construction process.  

1. Dig out and lay the foundation of your choice
2. Build the frame and lay the flooring
3. Install the insulation and vapor barrier
4. Install the interior paneling, ventilation, lighting, and door
5. Install roofing insulation
6. Install your heater
7. Add the final touches and test your sauna

Should you build or buy your sauna?

If you’re that way inclined, it is absolutely possible to build your own outdoor sauna. However, many people are not interested in building a sauna on their own and it’s for those people that buying a sauna is a great option. 

A number of companies sell prefabricated sauna pods, capsules, and cabins. However, it is important to note that a lack of building regulations encourages saunas made from inferior building materials. For this reason, choose a reputable company such as Palmako UK for making your purchase. 

Palmako has a wide range of sauna types (such as pod, barrel, and cabin) and sizes. Built from high-quality Nordic spruce, these prefabricated kits come according to specification and include double-glazed sauna doors.

Basic electric and Nordic design heaters can be purchased along with the sauna, providing the convenience of dealing with one supplier for all your sauna purchases. On top of this, they have an installation option available, which takes all the work off your hands and allows you to just walk in and enjoy your sauna once it's complete. 

If you have a small garden space or backyard, then try this option:

Palmako Sarah Sauna - 3.2m x 2.2m

This small cabin style sauna with tinted glass is the latest addition to the Palmako Sauna Catalogue. Easy to assemble, this modern sauna is beautifully designed to give you maximum outdoor visibility. Easily placed near a cold plunge pool, you can get the best of both worlds. 

An alternative to the sauna cabin, which is a very popular sauna here in the UK, is the barrel sauna. 

Palmako Anita - 2.2m x 2.5m

Compact enough for any small space and mounted on timber support cradles, this barrel sauna is extremely compact. The front glass panel and door provide an opportunity for enjoying your outdoor space while you relax and get away from the stresses of day-to-day life. 

The barrel sauna is ideal if you’re looking for an option you can easily disassemble when moving or if you’ve decided to swap your sauna for another outdoor garden building. 

All Palmako saunas are expertly crafted in their state of the art factory and quality checked to the highest specifications. Each timber piece is labelled according to the specifications in the assembly manual, making this a great start for your first DIY sauna project if you like the idea of both buying and building!

Happy Sauna Days

And that brings us to the end of our article on how to build an outdoor sauna. Whether you have your heart set on building or buying (or both), you can achieve this dream by following the advice we’ve put together for you. 

With so many options to choose from, you can proudly help to recreate Britain’s bath culture. In times gone by, Bath Houses were a ubiquitous part of the landscape, and we say, “Let’s bring that back”.  The British Sauna Society agrees. 

References:

1. British Sauna Society