So, how do you turn a country cottage into a large family house without overreaching the bijou footprint or harming the green belt? Easy, just dig deep and build underground. Northern Housing takes a look at a ‘futuristic’ subterranean retreat in leafy Cheshire

There’s something of the iceberg to a new ‘country mansion’ that was built at Helsby Hill, Cheshire. That’s not to say the four-storey property is cool, except perhaps in the stylistic way, but that the visible peak of its construction belies the hidden depths.

Since the site was located within the green belt and is in an Area of Special County Value, planning restrictions were especially tight. The brief for the new home was for a spacious – in excess of 15,000 square feet – family home but planners decreed that the visible parts of any new property had to match the footprint of the original Hillside Cottage.

Liverpool-based design and construction firm RJ Lewis Projects was called in to resolve the knotty problem. The company soon dug up a suitable solution – literally – by coming up with a design for a largely underground building, which is due to be handed over in the New Year.

“The plot’s owner had been looking to create a large family home that caused minimal environmental impact, both on the surrounding countryside and in its day-to-day running,” said Simon Lewis, director of RJ Lewis Projects. “He called on RJ Lewis after traditional architects had been unable to offer the space and features he required while protecting the area and satisfying planning regulations. This needed anything but an off-the-shelf solution.

“At Helsby Hill we’ve needed to create completely new design features while also negotiating a planning minefield. We’ve worked extremely closely with the local authority to design and create a 15,800-square-foot home that offers the expansive, low-energy living space required, while having minimal impact on the surrounding countryside. Local councillors, planners and neighbours have all been involved in the consultation process.

“The design has enabled us to base the visible area of the building on the dimensions of the old cottage it replaced. The elements of the new home above ground are also broken up into smaller sections, again to reduce the overall impact.”

Work began in February this year when the existing cottage was demolished. After that what can only be referred to as quarrying began – chewing into the sandstone bedrock of the hill – to excavate the subterranean cavity that would host the bulk of the house’s structure. The traditional means to do this involves blast charges, but to protect the area the developers used ‘breakers’ instead – huge rock cutting wheels – to carve out the space.

The building’s main structure is a steel frame, with timber-framed and panelled walls, to create four levels of living space, two of these underground. Indeed, 85 per cent of the property is underground, including some of its luxury features such as the indoor swimming pool. So, isn’t it all going to be rather depressing for the occupants to live enclosed under artificial light?

Well, no. A vertical ‘light tower’ carries natural daylight below ground and there is an internal courtyard that allows light into the ground floor without being visible to the surrounding area.

In terms of mod cons, swimming pool aside, the home is served by its own water borehole, uses bio-fuel energy and has its own waste water treatment plant. The light tower also incorporates an ‘energy free’ ventilation system. Home automation systems have been put into use to manage the home’s energy consumption for energy efficiency.

Below ground, the structure is free-standing from the quarry dug to accommodate it, so that it is surrounded by a cave that provides service access to every room, as well as insulation. The roof is covered by a lawn so that it blends into the scenic hillside. The backdrop to the site features the existing orchard along with the original trees and hedges. In many respects, it’s almost as if the below-ground structures were never there.

“Over the 30 years RJ Lewis has been in business we’ve tackled many unusual assignments but the project on Helsby Hill has been unique,” said Lewis.