Bespoke outdoor sauna installation, Putney: South West London
May 13, 2021
For this project, we installed an authentic bespoke outdoor sauna into a stunning outbuilding at the end of the garden of a beautiful property in Putney, London. The addition of a traditional Finnish sauna forms part of a larger house project and within the outbuilding, there’s also a small anteroom, steam room and shower area. Our client loves music and wanted a system integrated into the sauna space.
We aren’t ones to shy away from a challenge and made sure to source a quality audio solution that is designed to withstand the intense heat and steam of the sauna. Our client primarily wanted the sauna for himself and his wife but since inviting his kids in for the first time they are now massive Finnish sauna lovers and the whole family all regularly enjoy sauna sessions together.
At the preliminary investigative stage, we collaborated with the builders of the the outbuilding finding out the wall thickness and the materials they used. We then carefully worked out the computational volume of the sauna and ended up specifying the high quality Narvi smooth 9kW electric sauna heater to heat the ~13m3 room. The Finnish made heater fuses the exemplary build quality of Narvi sauna equipment, with stylish, understated Nordic design. The market-leading 8.5 mm thick heating elements warm the sauna very quickly and have an exceedingly long lifespan as well as a very low risk of overheating. Our client originally wanted a wood-burning stove but lives in a ‘smokeless zone’ - helpfully, an app on his phone which allows him to play the sounds of a crackling fire over his sauna speakers, helps to fill that particular void.
Gorgeous thermally treated pine for the installation is created in Finland by heat-treating soft timber. During the process, steam is used as a protective gas and helps to prevent the pine from splitting and becoming damaged. The intense heat deeply dries the pine to its core as moisture is removed and it means the finished product doesn’t react to humidity changes as prominently as untreated pine and the risk of shrinkage, swelling and/or cracking is reduced. In fact, we only use pine that has been thermo-treated due to raw pine’s poor natural characteristics. Without this treatment, pine is highly unsuitable for use in sauna constructions as it belongs to the lowest durability class and weeps molten resin. Thermo pine, on the other hand, does not suffer from any of these issues and is considered a durability class two timber; able to survive outdoors for up to 25 years.
Classic set up
A classic L shaped lower and upper bench sauna design was chosen to create a social aspect and to maximise the view out a window that looks back up towards the main house. The set up also provides the perfect height in order to enjoy the heat and steam at the top of the sauna or to rest lower down in less intense heat. Two air intakes ensure ample ventilation with fresh room temperature air brought in near the base of the heater and from under the glass door. Once heated, it rises and circulates around the room before being ducted out of the sauna opposite the heater, under the bench.
The design also includes a moveable, freestanding step that assists with access to the benches and it can be removed during cleaning. A well-sealed, durable vapour barrier surrounds the sauna to prevent interstitial condensation and the damp and rot that it can lead to. The effective vapour barrier also helps to contain the löyly, maintaining a more even humidity throughout a session. The end result is a quality Finnish sauna that is truly enjoyed by the family. In Finland, taking a sauna is an experience that is typically enjoyed for a lengthy amount of time - a minimum of half an hour- and includes cold plunges/cold showers. It’s not something simply tolerated for a few minutes after a gym session.