Click here for a video tour of Monty and Claire's home

Monty Ravenscroft and Claire Loewe’s four-bed family home in southeast London has a retractable glass roof in the sitting room, a double bed that slides back to reveal a bath, and a lavatory in a space the size of a cupboard, which doubles as a wet room. Perhaps the most remarkable thing about this curious structure, however, is that it cost just £170,000 to build.

The property, at 15½ Consort Road, in Peckham, is, in Ravenscroft’s words, “a culmination of 10 years of hassle”, even though the construction itself only took 18 months. It has been, he adds, “a journey of discovery”, during which he has learnt a lot: how to hoist a steel frame without a crane, for example, and how to create a house that is light and airy despite having no windows (the neighbours are too close).

Intrigued? Next weekend, you can see for yourself. Ravenscroft and Loewe, both 40, are opening their home to the public as part of London’s annual Open House weekend, a celebration of architectural diversity that allows you to visit everything from the Bank of England to Chiswick Business Park. Number 15½ is one of the wilder and wackier of the 70 private homes on view – and provides an idea of the wonders you can create, even when money – and space – is tight. “This is what you get on a budget,” says Ravenscroft.

Their house sits on a narrow plot of land (3,068 sq ft) between two graceful listed Georgian houses. It is partially hidden by bamboo, and its cedar-clad exterior blends into the surroundings. The initial impression is of a substantial garden shed with a generous driveway.

Inside, the one-storey space opens up like Doctor Who’s Tardis. Although only on a single storey, it has a mezzanine-level “pod” at either end and a giant lean-to at the front, with folding doors that allow the room to be used as a garage, a party space or, in this case, a mirrored dance studio – with cherub-painted ceiling and chandeliers – where Loewe teaches the tango.

From the main entrance, you can see the whole length of the house, through the living room and master bedroom to the garden beyond. It makes the place feel enormous. The living space incorporates the kitchen; and, thanks to the retractable glass roof, it is light and airy, even though it has no windows.

With the roof folded back, sunlight pours in, and it feels like an outdoor courtyard; at the first drop of rain, it automatically slides shut. In place of a window, there is a giant photograph of New York on the wall behind the sink and hob. “We don’t have a view, so I wanted the kind of view we might have had,” says Ravenscroft – even if Peckham is no Manhattan.

To the left of the front door is the main wet room. With space at a premium, a lavatory is concealed under a counter top, while the light fitting doubles as a shower head. Such tricks are repeated in a second wet room at the rear: the washbasin is tucked into a drawer when not in use.

There are clever touches elsewhere: in the front mezzanine “pod”, reached via “floating” steps, a single day bed in a spare room/study can be converted into a double by sliding out its three large drawers and pulling a platform over them. In another bedroom in the rear pod, one drawer mutates into a bedside table, there is concealed bedding storage, and another drawer folds down to shut the room off from the stairs.

Thanks to the sloping walls, nooks, crannies and concealed storage, it is a bit like being on a boat – no accident, as Ravenscroft has spent a lot of time on the water and was heavily influenced by boat design.

The overall effect is glorious – an Alice in Wonderland dream. Not that any of it was easy. It took Ravenscroft, who works as an actor, designer and film-maker, four years to find the plot, which he bought at auction for £40,000 in 2000. Winning planning permission, with a design by the late Richard Paxton, took another two.

Ravenscroft’s fluctuating income, together with the unusual design, meant no bank wanted to lend. His father ended up remortgaging his own house, and the couple borrowed the rest from friends. They did much of the work themselves, and there was the added stress of being filmed for Channel 4’s Grand Designs during the build. But it has been worth it: they love the house, and it was shortlisted for the regional Riba awards last year.

“I’m very happy with everything here,” Loewe says. “It’s fantastic.”

More than 660 buildings – including the 2012 Olympic site – are open for this year’s event. Entry is free, but booking is necessary for some properties. For details, call the Open House hotline, 0900 160 0061, or visit www.openhouse.org.uk

Open season

Eco-warriors: Want to see a timber pellet-boiler in action? Visit 17 Rowe Lane, a timber-framed family home in Hackney (above). In Hampstead, 27A Redington Road is a new-build with sheep’s-wool insulation and rainwater storage.

Minimalist purists: Garden House, on Haverstock Hill, Hampstead, is a glass edifice on an infill site; 9 Wilton Way, in Hackney, also has swathes of glass.

Modernists with kids: 53 Gayton Road, in Belsize Park, is a Victorian terrace revamp with a four-storey staircase, a garden extension in glass and steel, and a rooftop terrace; 32 Sotheby Road, N5, is an 1890s terrace transformed into three open-plan levels.

History buffs: choose from the only surviving Jacobean mansion in London, Charlton House, in Greenwich, with its minstrel hall and grand salon; or the grandeur of a restored medieval tithe barn in Harmondsworth, Middlesex.

Way-out wacky:see rubber floors and colour-changing lights at 61 Courtfield Gardens, a basement conversion in South Kensington

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