The clip-on revolution, you might think, ended long ago with sunglasses, ties and earrings. But it is stirring once again in a housing market stifled by recession and facing the need to become more sustainable.
Jim Whiston and Elaine McFarland have just gained an extra room at their traditional stone villa in Ardrossan, Ayrshire - and the neat, black box is the prototype for what could one day be a mass-produced, "clip-on" extension.
The clever structure may be the sustainable alternative to the conventional extension, since it provides a cheaper, greener alternative to demolition when there's a change of owner - or a change of heart.
A clip-on extension can be removed or replaced. If it were developed further, the idea might even result in some kind of extension swap shop. For the moment the Ardrossan version is merely the embodiment of an ideal, but its potential to bring about radical change is clear.
It is the work of Do, a Glasgow-based architects' studio. "At the beginning of the project we looked at timber-frame systems on the market which you can potentially pre-make and assemble on site," says Do's Adrian Stewart.
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"We decided to build it rather than clip it on, as we took into account the preferences of the builder and the constraints of the budget. But it could quite easily have been clipped on.
"If we do this kind of structure again, we would try to prefabricate it and bring it in as a kit. Building this way would take less time and, if it could be mass-produced, the costs would come down and it could be affordable."
Whiston, who is housing director for Ayrshire, and McFarland, a professor of history at Glasgow Caledonian University, were happy to embrace the experiment. Indeed, a large part of the idea came from Whiston himself.
"While living in Ireland, I picked up the yearbook of the Architectural Association of Ireland and there was a house in Dublin that had a little box on the back that connected with the garden," he says. "We liked the idea of the clip-on box, because, in theory, we could take it off if we wanted to. So we discussed this with Adrian.
"We were looking to expand our kitchen at the back of the house and create a greater connection with the garden, where we spend a lot of time. We've been in the house for 22 years now and nothing much has been altered, just a slap of paint here and there.
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"We still had the previous owner's DIY cabinets and an old Rayburn in the kitchen. But when we had to replace the Rayburn, it created a lot of disruption and it was then that we thought about going the full hog and extending the whole kitchen."
The relatively small size of the extension meant that planning permission was not needed, and the cantilevered box extension was built using a timber-frame structure with steel beneath for extra support.
A black-fibre cement tile, which has been used for the cladding and roof, was chosen for its simple, streamlined appearance, low-maintenance credentials and affordability.
"There was no desire to blend the new extension with the original house," says Stewart. "The idea was that the simple black box would clip onto the side, in a parasitic way, making a deliberate statement that it's not trying to be part of the original house.
"It would have been much easier if it had been supported off the ground, like a traditional lean-to or extension, but we were keen to have it cantilever off, for both aesthetic and practical reasons.
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"For example, we wanted to lift it off the ground to provide a protective ledge for the couple's four cats, Sweet Pea, George, Snapper and Yogi. This means that they now have a wee place to shelter in the garden."
There are other clever bespoke details that Whiston and McFarland are delighted with, particularly the main window's unusual opening mechanism, which folds up rather than opens out and acts like a canopy.
"It's like being in a street cafe," says Whiston. "And when we get rain, it offers a lot of shelter."
The beautifully crafted interior finishes, including the window, the island and the timber, cantilevered balustrade around the external balcony, were created by the Glasgow-based craftsman Joachim King, of Reformthenorm.co.uk. He recreated the 1950s feel of the couple's former kitchen while giving it a clean, contemporary edge.
The construction took longer than expected - about 20 weeks - but, says Whiston, it taught him a new skill. Having only the microwave at their disposal throughout that period made Whiston something of a microwave cooking expert.
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The couple are delighted with the total construction cost, though - it came in at about £30,000. They are clearly thrilled with what they got for their money.
"Although it only adds on about 43 sq ft, when you take into account opening up the thick external walls and the way that the circulation spaces have been opened out by taking away the old vestibule and partitions, it feels like double the size of the original kitchen," says Whiston.
"A lot more usable space has been created. It adds so much to the character of the house - which already has a lot of character."