The owners of this house liked their neighbours' extension so much they found out who the architect was so they could have something similar

ONE OF THE owners of this Edwardian house in Highgate, north London, the daughter of an Irishman who made his fortune in London, grew up here. As an adult she returned to live in the house with her husband and, when they decided to open up the rear of their home to let in more light, they only had to nip up the road to find an architect.

Looking in through a neighbour's bay window they saw just the sort of extension they wanted and knocked on the door to ask the owners who their architect was.

The fact that they could see the extension from the pavement shows just how successfully architect Brendan Woods, who grew up in Bangor, Co Down, had tied in the old part of the house with the new.

Instead of sitting squarely off the back of the house, the flank wall of the extension slants in at an angle just beyond the end of the livingroom in the existing part of the house, taking the eye through to the garden and across to the new kitchen.

Opposite the angled extension wall, the garden wall has been slanted slightly the other way to create an exaggerated perspective.

Yet you can still read the original rectangular extension where the kitchen ceiling drops into the new space, accommodating the room above it, while the angled addition soars past it on a higher plane.

This all finishes at an end wall that parallels the original back wall, bring everything to a final straight line.

And, once the sliding doors are opened, this complete area (combining the interior and exterior) becomes a large rectangle, comprising kitchen, diningroom and garden. There are unofficial seats in the patio area created by having a corner step configured in such a way that it creates a double-height step beside it that works as a seat. The brick walls beside the flower bed makes another bum rest.

While the lower-floor plan, with new extension, mirrors that of their neighbours two doors up, the materials aren't the same. Design decisions are arrived at for all sorts of reasons and the type of flooring here was chosen for reasons of footwear.

In the neighbours' house, Woods had used Colombian pine but the owner of this house said that she wouldn't be able to wear stilettos on it. So instead, wide-plank engineered European oak floors were used and this dictated the use of oak on the triple-glazed sliding walls.

Here the moving parts are in thick timber that slides across galvanised steel supports. That steel structure continues up and across the ceiling appearing through the white plaster. Should you wish to study the steel frames from more closely you need only check-out the support beneath the glass dining table, designed by Woods, which mirrors the structural frame exactly, offering a scale model.

The table is at the same height as the lawn so, with the wall slid open, meals can feel quite picnicky. The oak floor rises up to window cill level so that the internal floor meets the external one.

While the galvanised steel and chunky timber offers quite a raw, natural palette, the clients wish (granted) for a dark, red glossy Poggenpohl kitchen has rendered the space rather luxurious.

And throughout the pristinely finished, mainly white interior, Woods has added in rooflights and storage in various places, including a clever, beautifully finished audio visual cupboard in the downstairs livingroom, by precision craftsman Matthew Marchbank, who made benches in the Tate Modern, commissioned by architects Herzog and de Meuron (he has gone on to do more work for them since, in a private house).

Upstairs, where the extension's sedum roof can be enjoyed from various rooms, the biggest splash is made by the bathroom that opens off the main bedroom. These two rooms are connected by a wide, ceiling-height door that opens on an inset pivot.

You are ushered past mirrored walls (with storage behind) towards the free-standing Philippe Starck bath. Interiors magazines were awash with these a few years back and so they might be seen as something of a cliché - but it is very elegant in this setting - perhaps standing to its timelessness.

The floor, which rises to the window cill level to create the feeling of an enclosing nest, is in Portuguese limestone, as is the walk-in shower.

It was originally meant to be in a Bulgarian stone but, says Woods, they experienced such cold weather during this project that it couldn't be got out of the quarry. In retrospect the Portuguese stone is quite apt as Woods is a fan of Portuguese architects such as Álvaro Siza and Eduardo Souto de Moura (who worked together on the Portuguese Pavilion in Expo 2000 in Hanover and London's Serpentine Gallery pavilion in 2005). The metallic handles on the mirrored cupboards, made by Woods, are a reference to de Moura.

Woods designs pieces of furniture in many of his buildings - there is also a plywood bed in this house - and he still draws all of these projects the traditional way, by hand. The design of this extension - with its simple materials and considered form - shows a craftsman at work.