Underground

House

The Brief and Site Challenge

The project involved replacing an existing garage at the lower end of a steeply sloping garden with a new dwelling accessed from the rear elevated road. The original house retained its existing front access and was sold to finance the development—a common arrangement for maximising the value of constrained urban sites.

The site presented significant challenges. The garden falls away dramatically from the rear road, with a level change of at least four metres between the upper road level and the lower garden. This steep topography, combined with the constrained plot dimensions, created complex design and planning hurdles.

The proposal faced considerable planning obstacles. It was initially viewed as overdevelopment—introducing a new dwelling within a garden contrary to local planning policies on back-of-plot development. Additionally, the prospect of a two-storey house adjacent to a neighbouring bungalow was considered detrimental to the established street scene character. Previous architectural attempts to secure planning permission on this site had been unsuccessful.

The Design Solution

The scheme adopts an innovative inverted arrangement that transforms the site’s constraints into architectural opportunity. Bedrooms occupy the upper level at road height, whilst living spaces spread across the lower garden level. This upside-down house configuration places the principal rooms where they benefit most from natural light and garden connection.

The lower level features an enclosed courtyard garden with seamless access through large folding doors into the open-plan living space. This creates a private external room sheltered from overlooking and street noise. The upper level provides a terrace overlooking the garden, offering residents outdoor space on both floors despite the tight site.

Materials were selected for longevity and to deliver a sleek, contemporary aesthetic: zinc roofing provides durability and a distinctive profile, aluminium windows offer slim sightlines and low maintenance, whilst self-coloured render creates crisp elevations that won’t require painting. A town garden to the front maintains street presence, whilst the courtyard garden to the rear becomes the home’s private heart.

Technical Innovation and Construction

The construction employs a sophisticated hybrid approach that responds to the site’s technical challenges. A waterproof structural concrete box forms the below-ground level, preventing groundwater ingress—a critical consideration given the partially sunken design. The concrete structure provides the waterproofing integrity essential for underground construction whilst contributing significant thermal mass for energy efficiency.

A timber frame system built off the concrete box creates the upper storey, offering faster construction and lower costs compared to an all-concrete approach. This combination delivers both the robust waterproofing required below ground and the construction efficiency benefits of timber frame above.

Planning Success Through Sensitive Design

The design’s key planning success lies in its sensitive response to streetscape concerns. From the road, the house presents as a single storey, reading at the same height as the neighbouring bungalow. This visual modesty satisfied planning requirements regarding building height and impact on the established character.

By sinking the principal living accommodation into the ground, the design eliminates overlooking concerns whilst creating the internal volume the clients required. The house achieves substantial internal space without the external mass that had derailed previous proposals.

The Completed Home

The finished design delivers a confident contemporary town house that provides an attractive counterpoint to the dated architecture of the surrounding street scene. Rather than mimicking mediocre neighbours, the house asserts quality modern design whilst respecting the streetscape through its restrained single-storey presentation.

The sustainable credentials extend beyond the photovoltaic panels. The concrete lower level’s thermal mass moderates temperature fluctuations, reducing heating demand, whilst high insulation standards throughout minimise energy consumption. The hybrid construction approach also reduced embodied carbon compared to all-concrete construction.

The project attracted significant industry attention. NASBA (the National Association of Self-Builders and Architects) featured the house at Ecobuild, recognising its innovative approach to difficult site constraints. The design was also displayed at the Bath and South West Homebuilding and Renovating Show, demonstrating its appeal to the self-build community seeking creative solutions for challenging plots.

This project exemplifies how thoughtful design transforms planning obstacles into architectural opportunity. The constraints that defeated previous proposals became the drivers for an innovative solution—an underground house that delivers space, light, privacy and energy efficiency on one of Frome’s most challenging residential sites.