ESSAY IN SPACE AND LIGHT

THE CONTRAST is startling. One minute you are in the bustle of Portobello market, in west London, stepping over hit-and-run fruit and rumpled men drinking cans of lager out of brown paper bags. The next you are standing in perfect white space, gazing heavenwards and listening to the architect Pip Horne serenade his own creation - a forgivable conceit in the circumstances. For how often do architects in this country, without rich parents to fund their vision, ever get to build their dreams?

The house, built for a friend who prefers not to be named, is one of a unique private development of five houses designed by four architects, enclosed in a self-contained courtyard. All are distinctly modern, but Pip's house, with its playful geometry, rhythmic curves and slots of light cut through from top to bottom, is undoubtedly the most dramatic. Until this house was commissioned Pip's work since leaving the Royal College of Art in 1976 had consisted of what he calls "modest little interventions": extensions to houses, nicely done but low-key affairs. But this was the big one, the opportunity to express ideas that rarely get heard, let alone seen, in this land where even supermarkets have pitched roofs.

That said, he would not choose to go through the process again in a hurry. Working independently and yet in co-ordination with other architects using the same contractor presented an explosive situation: all those egos (and there's no doubt architects have big ones) rubbing up against each other. "We started off imagining there could be some kind of communality or sympathy in the external treatments but in the end it became quite heated," Pip remembers, "with everybody being rude about each other's designs. So because we couldn't reach a consensus we all did our own thing."

The whole project has taken two years, and aged Pip by 10. Both client and architect talk of the building work in the tones of those suffering from post-traumatic stress. Inevit-ably, perhaps, Pip felt the builder did not understand the house; typically, the exposed concrete ceilings aroused the usual builderly, "what, you mean you're going to leave them like that?" response. And the client, who was not brought up in England, found the lack of pride in building work profoundly depressing. "It seems that building here is something you do when you can't do anything else. And it's very difficult to build something beautiful out of indignity."

Ultimately, though, both architect and client are agreed on the outstanding qualities of the house: space and light. Even on a grey day the interior is rich in light which washes down the northern wall, and when the sun is shining the whole house is filled with a Mediterranean sense of well- being. But only an architect could call a house "an essay in light and space" and this kind of phraseology ("pompous, I know," Pip admits) highlights the difference between people who design houses and people who live in them. "Architects have different criteria," warns the client. "Space isn't the whole point of a house - comfort is."

In fact, though the client loves the house and considers himself modernist in taste, he finds that living in it has challenged some of his assumptions. "The lack of private space is a real problem. And it does make you think about why traditional houses are traditional. Maybe they were built in a certain way because they worked." Acoustics is another drawback of the flowing open space; when the Hoover is on downstairs and you are sitting in the living-room gallery the experience is similar to sitting on the runway at Heathrow. The client, who is peculiarly sensitive to noise, is adamant (but don't tell Pip) that he will close off the master bedroom, which at present has a stunning if vertigo-inducing open balcony majestically presiding over the whole space. But he is willing to accept that this is a different way of living that demands adaptation: "I yearn for private space, but it may just be that I have to learn another kind of privacy. And in compensation the house has a great sense of peace which comes from the arrangement of space and light."

Furnishing is another area of contention. With its underfloor heating, the house does not even have radiators to interfere with the sculptural quality of the interior, and Pip Horne accepts that it is not easy to choose furniture because the architecture is so dominant. "It's a question of living in it and then reacting to it in a positive way - making a confident judgement. You can't just plant little pieces of furniture here and there. The scale is very important, you have to make simple but broad statements," he insists, looking critically at the client's choice of Arts & Crafts dining chairs which do not seem to him to make a broad enough sweep in the cavernous ground-floor living space. "I mean, I know those chairs are not right," he says with an air of resignation, "but it's not up to me and I guess that's just something I have to grapple with."

For the client's girlfriend, who is about to produce their first baby, living with builders has not produced ideal nesting conditions. "It's only in the last few weeks, since they have gone, that I feel we have really been able to take possession of the house." But while accepting that urges to plaster the baby's room with images of Winnie the Pooh are temporary conditions of insanity induced by pregnancy, she still feels that the nursery needs to be softer. Carpets have been put down in it and the guest room next door without any damage being done to architectural credibility, while a huge sofa has carved a comfort zone out of the ground- floor living space. "I thought it was going to be easy furnishing the house but in fact even hanging pictures is difficult. The trouble is that everything becomes an `object' in the space; it all takes on such aesthetic importance, which I find difficult." The temptation, then, is to leave the space as empty as possible but that, they soon realised, was a kind of cowardice which architects and designers, in particular, are guilty of disguising as a kind of moral superiority. Eventually, they say, they will probably fill the house with lots of furniture, and to hell with "purity".

It's tempting to compare architecture with surrogate motherhood: you go through all the hard work of pregnancy (an elephantine gestation in this case), the trauma of giving birth and then you have to watch someone else walk away with your labour of love and raise it in ways you might not have chosen. "In a way it is my house," Pip admits. "In fact, I feel rather aggrieved at having to allow someone else in there. It was quite a wrench to let it go."

Happily, the bonds of friendship have proved stronger than the stress of working together so Pip will have access to his baby. But as far as the client is concerned Pip's role is over. "An architect can give you spiritual comfort that allows you to occupy the space - but he can't give you the comfort of a fat sofa and a soft carpet."