Bespoke Indoor Sauna Installation: Old Church House

The Old Church House project is a bespoke indoor sauna installation that holds a special place in Finnmark Sauna’s portfolio. Designed for a Finnish client with a deep, lived understanding of authentic sauna culture, this build had to meet the exacting standards of someone who had grown up with the tradition.

There was no room for shortcuts, compromises, or design decisions that prioritised aesthetics over function. Every element, from the heater selection and timber species to the bench arrangement and glazing specification, was chosen to deliver a sauna experience that would feel genuinely familiar to someone raised in Finland.

Set within a characterful residential property, the installation presented a series of technical challenges that demanded creative engineering and precision craftsmanship from our team. Bespoke arch-head door frames, custom secondary glazing, and Low-E curved glass were all designed and fabricated specifically for this project, ensuring the sauna integrated seamlessly into the existing architecture while performing to the highest thermal standards. Completed over an eight-day on-site build, Old Church House is a testament to what can be achieved when genuine Finnish sauna knowledge meets Finnmark’s design and installation expertise.

Project Specification

The Heater: Tulikivi Tuisku 10.5kW with TBH Soapstone Cover

For a client with Finnish heritage and an instinctive appreciation for quality, the heater needed to be exceptional. The Tulikivi Tuisku 10.5kW with TBH soapstone cover was the natural choice, a premium electric sauna heater from one of Finland’s most respected manufacturers, encased in exclusive Finnish soapstone that is over two billion years old. Tulikivi has built its reputation on the unique thermal properties of soapstone, a material that absorbs, stores, and radiates heat with remarkable efficiency. The result is a heater that delivers a gentle, even warmth long after the elements have switched off – a quality that transforms the sauna experience from a brief burst of heat into a lingering, deeply relaxing session.

The TBH soapstone cover gives the Tuisku its distinctive appearance, a sculptural, natural stone exterior that makes it a centrepiece of the sauna rather than a utilitarian appliance. Because each piece of soapstone is unique in its veining and colouration, no two Tulikivi heaters look exactly alike. This individuality resonated strongly with the Old Church House client, who valued authenticity and natural materials above all else. For a deeper look at how stone and natural materials can be integrated into sauna design, see our dedicated guide.

Beyond aesthetics, the soapstone cladding provides a practical advantage: it significantly reduces the surface temperature of the heater body, which in turn allows for smaller safety distances to combustible materials such as timber benches and cladding. In a residential sauna where space is always at a premium, this reduced clearance requirement gives our design team greater flexibility in the layout, enabling more generous bench dimensions without compromising safety. The soapstone surface will get warm, but it will not burn if accidentally brushed against, an important safety consideration that makes Tulikivi a particularly popular choice for family homes.

The Tuisku’s 60-kilogram sauna stone compartment ensures a generous mass for steam production. When water is poured over the stones, it produces the soft, humid löyly that defines a genuine Finnish sauna – exactly the kind of experience the client was seeking.

The Controller: UKU Black Glass Wi-Fi

The Tuisku is paired with the UKU Black Glass Wi-Fi controller, a sleek, minimalist touchscreen panel that can be wall-mounted outside the sauna room. Its black glass fascia provides an understated, contemporary aesthetic that complements both modern and traditional interiors. Through Wi-Fi connectivity and the dedicated mobile application, the homeowner can preheat the sauna remotely, set temperature targets, programme heating schedules, and monitor the sauna’s real-time temperature curve from anywhere in the house or beyond.

For a Finnish client accustomed to daily sauna use, this convenience is not a luxury; it is a practical necessity that reduces friction in the routine and ensures the sauna is always ready when needed.

Timber Selection: Thermo Aspen

The timber for Old Church House was Thermo Aspen throughout, a choice that speaks directly to the client’s Finnish roots. Aspen is the quintessential Finnish sauna wood, used in saunas across Finland for generations. By specifying the thermally modified variant, the client gained the heritage and familiarity of aspen with the enhanced performance characteristics that modern thermal treatment provides. To explore the full range of timber options for sauna builds, see our comprehensive guide: Best Wood for Saunas (& Why).

Thermo Aspen is created by subjecting natural aspen to a controlled heat and steam process at high temperatures, fundamentally altering its cellular structure without the use of chemicals or preservatives. The treatment transforms the wood’s naturally pale, creamy-white colour into a warm, rich honey-brown tone with a distinctive toasted aroma, a subtle, pleasant scent that many sauna enthusiasts find evocative and comforting. More importantly, the process dramatically improves the timber’s dimensional stability and moisture resistance. Thermo Aspen will not warp, cup, or shrink under the extreme heat and humidity cycles that a regularly used sauna demands, making it an exceptionally durable choice for both wall cladding and bench surfaces.

For the cladding, Thermo Aspen 120 was specified, a board width that strikes a balance between visual impact and practical installation. The 120mm profile creates clean, contemporary lines on the walls and ceiling, with enough width to showcase the natural grain variation of the timber while maintaining a sense of rhythm and proportion across the room. On the benches, the same Thermo Aspen was used, delivering a unified material palette and ensuring that every surface the bather touches shares the same warmth, smoothness, and low heat conductivity that makes Aspen so comfortable in a sauna environment.

Thermo Aspen is also hypoallergenic and entirely resin-free, meaning it will never produce the sticky, unpleasant exudations that some untreated softwoods are prone to at high temperatures. For the Old Church House client, who intended this sauna for frequent, daily use in the Finnish tradition, this long-term reliability and comfort were essential. 

The Juniper Feature Wall

As with many of our premium bespoke installations, a juniper decorative panel was selected to serve as the sauna’s focal point. Handcrafted from cross-cut slices of real juniper stems and arranged in a mosaic that is unique to every panel, the juniper feature wall introduces an organic, artisan texture that contrasts beautifully with the linear profile of the Thermo Aspen cladding. In Finnish and Baltic sauna tradition, juniper has been valued for centuries for its aromatic and therapeutic properties. When the sauna heats up and humidity rises, the juniper releases its characteristic essential oils, filling the room with a fresh, resinous forest scent that promotes respiratory health and deep relaxation.

For the Finnish client at Old Church House, the inclusion of juniper was not simply a design choice; it was a connection to a deeply familiar sensory experience. The scent of juniper in a hot sauna is immediately recognisable to anyone who has bathed in Finland, and its presence here grounds the space in the cultural tradition that inspired it. The panels require virtually no maintenance; if the fragrance diminishes over time, it can be refreshed simply by moistening the surface or lightly sanding with a fine abrasive.

Bespoke Engineering and Glazing

Low-E Curved Glass

One of the most technically significant features of the Old Church House sauna is the Low-E curved glass. Low-E (low-emissivity) glass features a microscopically thin metallic coating that reflects radiant heat back into the sauna room while allowing visible light to pass through. The practical effect is substantial: by reducing the amount of heat that escapes through the glazed surfaces, the Low-E coating improves the sauna’s thermal efficiency, brings down the computational volume of the room, and ensures better heat retention overall. This means the heater works less to maintain temperature, and the bather experiences a more consistent, enveloping warmth throughout the session.

The curved profile of the glass was specified to complement the architectural character of the property. In a building named Old Church House, there are inevitably period features, arches, curves, and proportions that a thoughtful sauna design must respect and echo. The curved Low-E glass achieves this, softening what could be a stark, modern insertion and instead creating something that feels sympathetic to its surroundings. Engineering curved glass to the required radius, with a Low-E coating that performs reliably at sauna temperatures, is a specialist undertaking, and one that demonstrates the lengths to which Finnmark will go to deliver a result that is both technically sound and aesthetically right.

Bespoke Arch-Head Door Frames

To match the curved glazing and the architectural language of the property, bespoke arch-head door frames were designed and manufactured using a CNC machine. CNC (Computer Numerical Control) machining allows for exceptional precision in shaping timber – the curved profiles of the arch heads were programmed digitally and cut to exact tolerances, ensuring a perfect fit against the curved glass and a clean, consistent radius that would be extremely difficult to achieve by hand alone. The result is a door assembly that looks as though it has always been part of the building’s fabric, rather than a recent addition.

This level of bespoke fabrication is a hallmark of Finnmark’s approach to installations in period or architecturally sensitive properties. Where standard rectangular door frames and flat glass panels would have jarred against the character of Old Church House, our design team instead developed a solution that celebrates the building’s existing form and incorporates it into the sauna design.

Bespoke Openable Secondary Glazing

The property featured existing windows that needed to be retained but could not be left exposed to the extreme heat and humidity of the sauna environment. Our solution was a bespoke openable secondary glazing system, designed and fabricated specifically for this installation. The secondary glazing sits on the sauna side of the existing window, creating a protective thermal barrier while still allowing the window to be opened when the sauna is not in use, providing ventilation, access for cleaning, and the ability to enjoy natural light and views. This approach preserves the original windows, maintains the external appearance of the property, and ensures the sauna environment remains properly insulated during use. For anyone undertaking a similar project, our DIY Sauna Build Guide covers the principles of glazing and ventilation in sauna design.

Bench Layout: Traditional Finnish Opposing Arrangement

The bench layout at Old Church House was driven entirely by the client’s Finnish heritage and their vision for how the sauna would be used. They specified a traditional opposing bench arrangement – two long benches facing each other across the width of the room – designed specifically to facilitate social bathing. In Finland, the sauna is not a solitary pursuit. It is a place for conversation, family time, and connection. An opposing bench layout encourages exactly this: bathers sit or lie facing one another, creating a natural, intimate setting for the kind of unhurried, communal experience that is central to Finnish sauna culture.

This arrangement also offers practical versatility. The opposing benches can comfortably accommodate multiple bathers sitting upright, or one or two bathers lying flat on the upper level while others sit below. The heater, positioned centrally, radiates heat evenly to both sides of the room, ensuring that every bather receives the same quality of löyly regardless of where they are seated. For the Old Church House client, this layout was not a preference – it was a requirement, rooted in a lifetime of authentic Finnish sauna experience.

The Installation Process

The Old Church House sauna was completed over an eight-day on-site installation, one day longer than a typical bespoke build, reflecting the additional complexity of the curved glass, CNC-machined door frames, and bespoke secondary glazing. The installation sequence followed our proven methodology: room preparation and insulation, framing and battening, cladding of walls and ceiling, construction of the opposing bench system, installation of the heater and controller, fitting of the bespoke door assembly and secondary glazing, installation of the juniper feature wall, and final commissioning and testing.

Every stage required close coordination between our design team and our on-site installers. The arch-head door frames, for instance, had been precision-cut in advance using the CNC machine, but their final fitting still demanded careful on-site adjustment to ensure a perfect marriage between the curved timber, the Low-E curved glass, and the existing structure of the building. This is the reality of bespoke work in characterful properties – no amount of workshop preparation can replace the skill of an experienced installer working with the building as they find it.

Why Choose a Bespoke Sauna Installation?

Old Church House illustrates the transformative potential of a bespoke sauna installation. No modular cabin or off-the-shelf solution could have delivered a sauna with curved Low-E glass, CNC-machined arch-head door frames, bespoke secondary glazing, a soapstone-clad Tulikivi heater, and a traditional Finnish opposing bench layout, all integrated within a characterful period property. This is what bespoke means at Finnmark: a sauna that is conceived, designed, and built entirely around you, your space, and the way you want to bathe.

With a bespoke installation from Finnmark Sauna, clients gain access to our full range of premium Finnish heaters, our extensive selection of sustainably sourced sauna timbers, and the expertise of our in-house design and installation team. We manage every aspect of the project from consultation through to completion. Explore more of our completed projects in our sauna case studies.

As the UK’s first “Sauna from Finland” certified retailer, Finnmark Sauna brings an unmatched depth of knowledge and authenticity to every project. Whether you are converting an existing room, building a garden sauna, or integrating a sauna into a period property, our team is here to guide you through every step.

Interested in a bespoke sauna installation? Contact our team today to arrange a free consultation and discover how we can bring your sauna vision to life.