Project Description

Creating a mini spa in a small garden with exposed steel beams and connections for a modern look.

SWJ Consulting was asked to work with Unity Architects in Leamington Spa, to design a luxury mini spa area in a small garden, with a cantilevered roof and exposed steel beams and connections.

The owner’s vision for the project was to make a feature of the steelwork connections throughout the development, inspired by the theatre constructed within the Royal Exchange Hall in Manchester.

Designed in 1976 by Richard Negri at Levitt Bernstein, the seven-sided theatre-in-the-round is suspended within the vast Victorian trading hall and is famous for its use of exposed tubular steel, dark structural framing, expansive glazing, and layered balconies and galleries, creating an almost spaceship-like design.

First things first. Foundation design and party wall agreements

The area proposed for the mini-spa was unused garden space around an existing double garage, in the garden of a 10-year-old house on a housing development. The design of the sauna and changing space, utilising this awkward space, meant that the new build would be adjacent to neighbouring structures.

Early in the process, SWJ Consulting requested trial pits to understand the ground conditions and ensure that the existing garage foundations could take the additional load without affecting the garage or neighbouring structures.

A party wall foundation was detailed with a compressible filler separating the existing and proposed foundations. This detail was adopted to accommodate differential settlement between the two structures and to prevent the proposed foundation from influencing the existing foundation as settlement occurs. The arrangement was also used to reach an agreement with the neighbours and formed part of the subsequent party wall agreement.

It was also agreed that the foundations would be constructed using a sectional hit-and-miss approach. This method was important in minimising the risk to the neighbouring property, as the foundation trench was excavated in short sections rather than continuously. By excavating and casting each section sequentially, the stability of the surrounding ground could be maintained and any effects on the adjacent structure could be monitored, thereby reducing the risk of ground movement or undermining of the neighbouring foundations.

Creating a ‘floating’ roof

To create an aesthetically pleasing meeting of the existing garage and proposed extension, an L-shaped roof was designed that wrapped around the garage and appeared to ‘float’ above the hot tub.

Using construction design technology, SWJ Consulting modelled and tested the framework needed to create a cantilevered roof retaining the architect’s vision of a slim and elegant profile.

Designing Exposed Steelwork and Connections

In most residential developments, structural connections are concealed to create clean architectural lines. At Carroll Drive, however, the client wanted the opposite approach. The exposed steelwork and visible connections were to be the defining architectural feature, reflecting the modern industrial character that inspired the project.

SWJ Consulting designed and detailed all exposed steel connections to create the required aesthetic while maintaining structural performance and buildability. The challenge was not only to achieve the desired appearance, but also to develop practical connection details that could be fabricated efficiently and installed within the project’s restricted working spaces.

To simplify site installation and maintain the clean exposed finish, SWJ Consulting incorporated the use of blind bolts with slotted connections and carefully coordinated steel interfaces. This approach enabled the complex connection arrangements to be assembled within a confined space.

Because the structural steelwork and connections remain exposed to view, long-term protection of the steel was a critical consideration from both a durability and aesthetic perspective.

External steelwork is continually subjected to environmental exposure, including moisture, atmospheric pollutants, and temperature fluctuations. With this project, the steel is also exposed to elevated humidity levels and airborne chemicals such as chlorine and treatment agents, all of which significantly increase the risk of corrosion if left unprotected.

To ensure the longevity and appearance of the exposed steelwork, a carefully specified protective coating system was required. Protective treatments help prevent corrosion, staining, and surface deterioration while maintaining the intended architectural finish of the exposed frame and connections. The selected coating system also needed to preserve the texture and character of the exposed steel, ensuring the industrial aesthetic remained visually authentic rather than over-finished or concealed.

Particular attention was given to junctions, connection details, and interfaces between steel and glazing systems, as these areas are often most vulnerable to moisture. Through careful detailing and coating specification, the exposed structural elements were protected without compromising the clean architectural appearance.

The result is a robust and visually refined exposed steel structure capable of performing within a demanding environment while continuing to express the project’s industrial design inspiration.

The benefits of collaboration from the earliest stages

Through close collaboration between SWJ Consulting, Unity Architects, Four Walls Building Company and IQ Glass, the project balanced architectural ambition with practical engineering solutions. It demonstrates how early engagement with structural engineers and collaborative working with the client, contractors and architect can deliver incredible results in the most constrained and under-valued of spaces.

Thinking pragmatically and value engineering all aspects of the design from the early stages enabled the development of more efficient solutions that mitigated the risks to the existing structure and neighbouring property and contributed to a successful party wall agreement.

Careful consideration of fabrication, installation, and long-term steel protection ensured that the exposed structural elements were manageable for installation, delivered the desired visual impact and will continue to perform and age successfully over time.

This is a project that celebrates structure rather than concealing it — combining engineering precision, industrial character, and architectural quality to create a unique and highly individual space.

To read more about this project, please read Unity Architects’ technical insight article

If you have a similar project or require advice on structural elements of a project, please get in touch with the Witney office 01993 225085 or Southampton office 02381 920656 or email mail@swjconsulting.co.uk