Bespoke Outdoor Sauna Installation, Chalfont Lane, Chorleywood: Hertfordshire

We feel that out of all our installations, this particular sauna may have one of the largest impacts on the lives of those using it. Saunas are most effective when they are used consistently as part of an active, healthy lifestyle – even more so when used from a young age – and this sauna installation was for a young family looking to do just that.

The foremost aim was to create a sauna that could be used as a place of relaxation and recovery, as the client’s busy work life and exercise-focussed hobbies (which includes practising the Wim Hof method of cold therapy, breathing and meditation) meant sauna bathing would provide a whole wealth of both mental and physical benefits. It was also of high importance to ensure this same sauna could be enjoyed by the entire family, including their young children, for years to come. 

Establishing the setting

The install is a good example of how we often work alongside firms who are already on site. The preliminary plan was to have the sauna accompany a pool house the clients were building alongside their existing hot tub and swimming pool. Initially, the clients wished for the sauna to have a separate access point from the pool house – with a glass door leading straight from the sauna and into the garden to allow for a view of the pool. However, having a glass sauna door leading straight into an external environment has the potential to create difficulties.

To begin with, it would require the additional use of sealed silicone, double glazed units, and wooden fixtures, fittings, and frames; all of which make the majority of experienced sauna installers view it as an impractical option. Further, security would be an issue since placing a lock onto a glass sauna door would require using heat-conductive metal and would create a trap risk for bathers. Finally, it removes the option of having a gap under the door to be utilised as a source of air intake for the heater and creates an issue of cleanliness from external debris entering the sauna.

To solve this problem, we decided to have the sauna be situated at the end of the pool house, with the door into the sauna located within the changing rooms. Since the original reason the clients wished to have an external glass door was to allow a large viewing area that could look onto the pool area, we designed the sauna to include a large, panoramic window. This window looked directly onto the swimming pool and was accompanied by another smaller window that looked up towards the house. To ensure a natural and seamless continuation of the pool house, the sauna’s window frames were painted a matching RAL colour the same as the rest of the construction.

Building the space

After experimenting with a few different layout designs, we decided that the optimal choice was a two-tiered L-shaped bench set up, to be accompanied by a Narvi Velvet electric heater placed at the end of the benching. This allowed for maximum utility of the space and created a laid-back but social seating arrangement where bathers can easily converse. 

For a plentiful introduction of natural light, and to ensure bathers were able to see into the pool area, we designed and installed the aforementioned panoramic window. The durability of this window was reinforced with double glazing and silicone seals to protect against the saunas harsh temperatures – something which causes issues of melting or warping in temperature-susceptible materials such as butyl sealant. 

Accoya wood frames were created to further assure this durability whilst also enhancing the window’s pleasant aesthetic. A well-earned reputation for dimensional stability and high durability means this long-lived wood was an ideal material for our purposes, as it will remain steadfast against harsh conditions for 50+ years whilst also taking paint and staining extremely well. In this case, the external surfaces were painted to ensure consistency with the existing pool house building while the interior surfaces were treated using specialised Supi sauna wax. This latter measure produced an attractive colour that perfectly matched the rest of the sauna’s timber and provided additional protection from the sauna environment. 

Turning it into a modern, family-friendly sauna 

Thermo aspen was chosen for the entirety of the sauna’s interior, except for the floor, which was tiled with a very attractive Stormstone shadow tile. This thermally stable, highly resilient wood was a perfect choice, as it is the ideal mix of beauty and resilience the clients were looking for; attractive deep tones, but with high durability and low maintenance to not get damaged by the children or their friends. Although other popular wood options like cedar are revered for their distinct beauty and strong aromas, they are often very vulnerable to scratches and damage. They are also not as well protected against damage or staining caused by chlorine – an important consideration for this build since the sauna was in such close proximity to the pool (although we do recommend always rinsing off any chemicals that may be on your skin before entering a sauna). 

A removable heater guard to protect the younger children was also created from the same thermo aspen, along with a movable step to help with bench access. Both of these additions were designed in such a way that they blended effortlessly into the overall layout of the sauna; their style and construction perfectly mirroring that of the existing benching. Although many people assume a sauna is not safe or suitable for children, it has been found repeatedly to have only positive effects, and indeed almost all Finns sauna bathe from around 5 months of age onwards.

To complement the rich beauty of the wood and refine the sauna’s attractive design and style, we recessed the heater into the benching; utilising the Narvi’s installation flange to make the recessing appear seamless. Taking this extra step established a smart, sleek aesthetic which was further enhanced by using under-bench skirting to hide the framework, alongside installing dimmable lighting along the backrests and bench lips to create a subtle diffusion of light within the space. 

The final and somewhat key factor that introduced a sense of modernity and made this installation stand out was the addition of a high-quality speaker system. Although an unusual and difficult addition to a traditional Finnish sauna, the clients felt that being able to listen to music whilst bathing would be the best way for them to relax and as such, it was something we were more than happy to try and make possible.

To ensure no damage would occur due to the saunas harsh heat and humidity, we created small waterproof speaker containers using the same thermo aspen wood as the rest of the sauna’s interior. These not only protected the speakers but also allowed them to blend effortlessly in with the rest of the sauna’s layout and style. They were then secured underneath the sauna’s benching where the environment is coolest and connected using heat-proof cables.  

Ensuring an authentic, high-quality experience

Although it was important that the entire family could enjoy the sauna, the main user was going to be the husband – who had sought us out specifically for our ability to provide a truly authentic Finnish sauna that would aid in relaxation and recovery. Due to a combination of a busy, stressful work life and various forms of strenuous activity by way of sports holidays and tennis, the gentleman had spent a lot of time researching effective ways to relax and promote physical wellbeing – realising that sauna could be highly effective. It was therefore important to him that the sauna not only looked aesthetically amazing but was built to an extremely high standard that would equal or even exceed the bathing quality of traditional Finnish saunas. After visiting our client sites, the couple were confident that we would provide the high standard of service they were looking for – especially after being disappointed by the quality of our cheaper competitors (many of whom use improper materials, do not adhere to Finnish guidelines, and/or do not have specialist sauna knowledge). 

Our standards involve religiously taking the time to ensure that all our saunas not only meet but exceed Finland’s extensive sauna regulations; all of which ensure a sauna will provide the experience, quality, and longevity of an authentic Finnish sauna. To begin the process for this installation, we set up an optimised, passive ventilation system. This ensured a consistently airy and clean environment where fresh heated air could be continuously introduced and properly circulated whilst already circulated air would be simultaneously expelled. This system also works to enhance the performance of the sauna’s heater; in this case, a Finnish-made Narvi velvet electric heater, which comes with an immense stone capacity large enough to ensure only the highest quality authentic löyly experience. 

Whilst all the timber we use is milled to grade-A standard and sourced exclusively from environmentally sustainable sources (usually from within Finland), the timber in this installation had also been thermo treated. It gives the timber the additional benefits of a pleasant smoky aroma, deep rich colouring, and massively increased durability. To guarantee even more extensive durability and longevity, Kingspan SPU Sauna Satu’s foil-backed insulation board was used to insulate and vapour seal the entire structure. This product ensured no long-term degradation or thermal bridging would occur like we frequently see with other, non-specialised products and was kept separate from the cladding by way of thermally stable high durability battening boards which ensured no moisture from the vapour barrier would affect the internal cladding.

If you would like to have a better understanding of the importance of adhering the Finnish sauna regulations as opposed to those in the UK, you can find the relevant information in our article: ‘UK sauna regulations, and how to ensure you are getting the real thing when it comes to traditional Finnish saunas’. Additionally, should you be interested in the health benefits of sauna bathing, we have a comprehensive series on the matter on our website here with all evidence collected exclusively from peer-reviewed scientific publications.