At home: Rae's Craigleith

While the house still looked traditional and respectable from the front, it was a different story at the back, thanks to the open-plan kitchen/family-room that replaced the old configuration, turning it into a sociable space in which to chat while cooking, listening to music or watching TV. Robert is now a convert...

"The back of the house is hidden so you don't see it right away and people aren't expecting it," says Sally's husband, Stuart. "But when they come through and see it, the reaction is always, 'Wow!'"

Just as the most successful makeover programmes steer people away from radical surgery in favour of making the most of existing assets, so architect Crichton Wood was able to make the home, at Orchard Road South in Edinburgh's Craigleith, look at least 10 years younger by pointing out that an extension was not so much what the Raes needed, but rather to make better use of the space they already had.

His solution was to open up the interior to the large garden, extending the boundary of the house by 3.5m in the space where the conservatory was, creating a new dining-room/sitting-room/kitchen and utility room, and a replacement pond that was an immediate hit with the local frogs.

"The house doesn't extend that much further out now, but the space has become usable, whereas it wasn't before," says Stuart. "The lounge had two French windows but not a huge amount of light, whereas now we have glass all the way across. The only downside is I can see all the things I need to do in the garden!"

Back in 2007, the house had a glazed conservatory that was too cold in winter, too hot in summer and was almost collapsing from damp. Unable to use it, the Raes began thinking about a solution. Moving was out as the house Stuart had bought 15 years before, because it offered space for the family pets, still suited their lifestyle and subsequent animals, and its location close to the city centre was ideal for work: Stuart is an accountant and Sally is in recruitment. The bungalow also had the advantage of a large garden that wasn't overlooked.

"So we thought we should stay where we were and add an extension," says Stuart. "We like clean, modern design and wanted glass, open plan and for the room to flow into the garden. Through the Ideal Home Show we got an appointment with Crichton, who came up with a fantastic solution that made better use of the space rather than adding a big extension. It was just so simple. What we have now hasn't changed at all from that first design."

With a drop of a metre and a half from the back wall to the garden, Wood facilitated access by gradually lowering the levels in the house, with a step down into the sitting-room, then a further one into the kitchen.

"I would never have thought like that," says Stuart. "It creates a bit of interest and increases the ceiling height. By the time you get to the kitchen there are only three small steps into the garden and the same from the balcony over the pond."

Architect Crichton Wood says it is a common misconception to consider an extension or conservatory when all that might be required is a simple reworking of the space you already have. "People stick on conservatories and all they're doing is creating a small box that's no use that they never use. It's better to take a wall out and reuse the space. The further you go out with a conservatory the more expensive it is and you may not have the budget for that."

Starting in April 2008, builders Melville Construction and Maintenance had the job finished by Christmas and while it was ongoing, the sitting-room door was boarded up and the Raes were happy to manage without a kitchen.

"We did the washing up in the bathroom and the clothes at the launderette. With just a fridge and a microwave it was like going back to student life. We never regretted the upheaval; it was all worth it," says Stuart. "We never tire of looking out at the garden or going out the back and gazing at the house."

One of the reasons the Raes are so entranced with their upgraded home could be Crichton Wood's application of the principles of proportion and the introduction of irregularity to give it a Mondrian feel.

"If you are building something symmetrical, you deliberately put something else in that is slightly out of proportion so it engages the brain, adds a tension, although you might not see it at first. At Orchard Road South, if you look at the elevations they are not regular; I have changed the levels and planes both horizontally and vertically. This brings the living-room slightly forward so even though it's open plan, it's a space of its own. Also, on the right-hand side, under the roof, the glass wraps round the building, allowing in light, shadows and a view of the trees," he says.

Creating the 56m sq space meant knocking down the wall between the sitting-room and kitchen, and the addition of a partition wall to create a utility room off the kitchen.

"It's a big, open-plan space and you don't want a washing machine in it. Sally and Robert like to cook, and they can be in the kitchen and chat with me in the lounge," says Stuart. "It's a family room and a great social space. We've had 20 to 30 people watching the rugby and it doesn't seem crowded."

With two-year-old golden retriever Djuma – named after the South African game reserve where the couple were married – and cats running in and out, an engineered oak floor was chosen. On the walls, the Raes wanted plain white to make the most of the light and keep an uncluttered feel, relying on the garden for colour.

"Crichton Wood is pleased we kept it so minimal but it's really because we can't afford to fill it with art, although we do have one very nice painting that was a wedding present from a friend," says Stuart.

Another important feature of the sitting-room is the chimney breast built at a 45-degree angle with a recess for a plasma TV, both creating a snug, homely feel.

A sound system installed by the people at Loud and Clear, who ran speaker wires into the ceiling and floor for a tangle-free finish, add to the room's credentials as a party space and might also explain why Robert is reconciled to the modern makeover of his hitherto traditional home.

And what's wrong with a granny in a mini skirt anyway – if she's got the legs for it? It's all a matter of proportion. k

Crichton Wood Architects, (01506 854798, www.crichtonwoodarchitects.com)

This article was first published in Scotland on Sunday on 07 February 2010