Interiors: Jed Water, Borders

For years Ann and John Roberts endured the absence of a view to the nearby Jed Water from their 200-year-old Borders farmhouse, originally home to the owner of the adjacent watermill.

"The miller, I suppose, never wanted to look at the river when he came home," says Ann. "But we do."

The couple, both journalists, and their three children moved to this rural location near Jedburgh in 1990. Extending was always a better option than tampering with the fabric of the B-listed house, and now they have more than doubled its size.

"Most people downsize when their children leave home," says Ann; "We did the opposite."

The couple liked the concept of introducing new architecture to the old, but feared the planners wouldn't agree. Yet when their local conservation architect visited, he indicated that he would be happy with a modern building.

It wasn't, however, until Ann and John saw a newspaper article on architect Mark Walker's Perthshire home that their idea came into sharp focus. Its expanses of glass struck the couple as the perfect means by which to open up their home to its magical setting. They also admired the untreated timber cladding that gave Mark's home – The Cedar House – its name. Cedar weathers beautifully and allows these buildings to slot unobtrusively into their respective settings.

Mark, who designed his home as a prototype, believes that extending a historic building like Ann and John's shouldn't mean having to create a pastiche of the original. "A representative from Historic Scotland wanted us to include stone in the extension's facade," says Mark. This would have compromised the clean-lined glass and timber design, and was technically impractical. "We would just have been sticking bits on," Mark says.

The couple's planning application was ultimately passed quickly and work began in winter 2004.

The extension was always intended to rest well with its older partner. Removal of a crumbling cart shed at the rear meant the new building could extend backward, following the width of the farmhouse. And if the extension's simple rectangular form resembles an agricultural barn, that's entirely fitting for the location.

Mark also examined the side profile of the farmhouse, to the rear of which a one-and-a-half storey extension was added years ago. Rather than bolt the new building to the old, he echoed the existing pattern of raised and lowered height by inserting a rectangular structure, the same height as the farmhouse, in advance of the new one-and-a-half storey extension.

"It's like carriages of a train shunting together," Mark says.

Cladding the old extension in horizontal cedar creates another visual link between old and new.

During the build Ann and John had their fair share of headaches – the first building team constructed the timber frame and steelwork before personal circumstances forced them to leave the job.

Neil Rose of Borders firm Ternion Joinery stepped into the breach. "This was a brave thing to do," Ann says.

Inserting conventional rooms within the extension would have broken up the glazed walls. Mark's solution was to wrap an open plan living space – kitchen, dining and sitting areas – on the outer edge, around a middle section that houses bedrooms and bathrooms. At the heart of the whole volume is a hollow core, a three-metre squared external courtyard that feeds light and ventilation to rooms on its periphery. Most of these rooms open onto the outdoor space where Ann grows plants and herbs.

Although river perspectives are north facing, glazing to three sides of the extension invites abundant light (blinds have been fitted to prevent heat build-up), while glass set into a south-facing roof slope channels brightness to the kitchen. Reflections of blue and red are cast against white walls courtesy of Perspex panels within the roof apex.

"We sourced Perspex transparent enough to let light through, but solid enough to disguise the rough timber beams," says Mark.

Ann's office is located on the extension's open-plan edge, close to stairs that rise to a little library where a secret sliding wall reveals a bedroom. Another door off this bedroom leads to the mezzanine above the kitchen, home to Ann's son's drum kit.

"It's like a minstrel's gallery," says Mark.

Underfloor heating eliminated the need for radiators, and the couple opted for a geothermal system. Ann was frustrated by the lack of accessible information available on this still-new technology.

"You only learn through using it," she says. The extension's insulation values are high, and Nordan double-glazing is Argon-filled for extra efficiency. If Ann were to do it all again she would install a solar panel to supply hot water in the summer.

The geothermal pump heats the original farmhouse too, although it's less effective with the old radiators there. The farmhouse insulation was also improved and some of its rooms were reinterpreted during the building work; the original kitchen, for example, is now a laundry room.

But the old building's character has essentially been preserved, its intimate spaces contrasting with the openness inherent to its new sibling. Fire ablaze, the farmhouse sitting room comes into its own during winter, when Ann retires there to listen to The Archers.

In contrast, the fireplace within the extension is a slick, recessed affair, while the wide-screen television is set back between bookcases (custom built, like those throughout the house, by Ternion Joinery) so it doesn't dominate.

The couple were fastidious with choices for the new interior; the slate floor has a red hue complementing the adjacent sandstone mill. An expensive extractor hood was necessary in the kitchen, given the open-plan nature of the space, but Ann kept the budget down for the units and worktop. Furniture such as clear bar stools from John Lewis was chosen for its unobtrusive appearance.

"The idea was not to have much inside so the focus is outside," Ann says.

Indeed, the most important results have been the light, space and above all, those river views. Watching ducklings learn to swim or the heron waiting for a fish are simple pleasures once hidden, but now joyfully revealed to Ann and John.

Walker Architecture, tel: [phone], www.walker-architecture.com

#149 This article was first published in The Scotsman on April 03, 2010