Perfect extensions: how to co-ordinate an extension and garden overhaul at the same time

This crisp, formal garden in Islington is the perfect partner for the new glass house extension, but the garden designer responsible, Declan Buckley, says this kind of precision design only works if the two projects are tackled together.

“Most people have the sense, especially when a change of level is involved, to call in the garden designer at the start, to work closely with the architect and do the major excavations and landscaping at the same time. It’s essential to co-ordinate extension and garden together for the best results with the least stress on everybody, including the clients. The materials for both can be married together, and there’s no need to be ferrying stuff through the house.”

For a start, the old garden, a neglected mishmash of shrubs and tatty lawn with no space for dining or entertaining, had to be dug up and removed.

“It was 1.2 metres above the house, the same level as the lawn is now, so more than 40 cubic metres of soil had to be skipped, although we kept some good topsoil for the raised bed at the back of the garden,” says Buckley.

He created a generous terrace that flows out seamlessly from the interior, which has the same floor of pale limestone for the first two metres. Instead of a steep flight of steps leading straight up to the garden — the predictable option — he designed a series of shallower steps, set at right angles.

These make an easy transition to the next level, a contrasting section of black basalt chippings which echo the dark anthracite brick surrounding the extension. “Dividing the garden horizontally makes it feel wider, and the pale stone further exaggerates the width of the garden,” says Buckley.

For the third stepped section of the garden, he rolled out an artificial lawn that stays green and maintenance-free through the year. “There was no option, because the back of the garden cast deep shade, due to surrounding trees and a catalpa tree at the far corner that had a preservation order, so a real lawn would never thrive.”

Buckley’s main plant materials of choice, to form the clipped green architecture that echoes the linear design of the garden, were yew, holly and box. He used yew plants to make a solid green wall around the lawn area, and at the back of the garden, just in front of the yew, he planted a higher level of berry-producing holly trees — self-fertile Ilex Nellie R Stevens — to create a glossy, evergreen screen.

“Extensions like this open on to a great view,” he says, “but unless you put up a screen, everybody around you gets a great view, too.”

Box effectively creates low, linear blocks throughout the space. At the back, the box edging that neatly frames the yew panels on either side is trimmed to the same 40cm height as the limestone retaining wall at the back, which is wide enough to double as a bench.

On the terrace, the double row of box echoes the shape of the two steps alongside, with the stepped effect achieved by installing a steel wall between the two layers of planting, to form a raised bed.

The drop at the left of the terrace is safeguarded by a glass balustrade, to avoid, says Buckley, the caged-in feeling that railings would give, and in the same way, a line of planting at eye level along the back of the terrace makes a pleasing alternative to a safety rail.

Late in spring, as well as the year-round lavender, lily-flowered orange tulip Ballerina contrasts with dark tulip Queen of Night and these are followed by alliums and Verbena bonariensis Lollipop, which provides a gauzy, 60cm-high veil of mauve flowers on slim, straight stems.

Later in the year, evergreen star jasmine and climbing roses on either side of the lower segment of the garden bring to the terrace the scents of summer, giving this streamlined garden the best of all worlds.