Designer David Bentheim brings a sense of permanence and harmony to this Californian new-build

When work drags you across the world with five children in tow, it can be a good idea to enlist help from a trusted source. Thiswas certainly the strategy for the owners of this newbuild in California. Returning to the US after a long stint in the UK, they called upon the British interior designer David Bentheim. 'We first met when I designed their London house eight years ago,' says David. 'By the time they relocated to San Francisco, we'd become friends. They asked me to work alongside their American architects.' Relocation, of course, is a gruelling process, but if you add to the disruption by building a new house, you can expect the task to seem overwhelming. This was particularly the case as the owners - originally from Chicago - were unfamiliar with local shops and services.

At the outset, their plan for the virgin plot in Palo Altohad been for a house in the Spanish Colonial Revival style, a look characteristic of the West Coast, but David pushed for something with a distinctly more European flavour. His tactful intervention between the well-understood preferences of the owners and their Californian architects, Arcanum Architecture - a firm that is known for its streamlined approach - proved decisive. 'In the end, we came up with an interior that was much less pure than first envisaged,' David says.

Externally, the house - roofed in terracotta and painted in shimmering white - would not seem out of place in Palma or Ibiza. Indoors, the Mediterranean sensibility is stronger still. The two-storey, five-bedroom house is laid out with the main living areas, including a drawing room, kitchen and dining room, and main bedroom suite on the ground floor and the remaining bedrooms above.

The intention throughout was to soften the modern with a been-there-forever charm. To rewind to the past, David suggested a variety of ceiling treatments, introducing slopes, lanterns and beams. 'It's the first time I've ever considered fake beams,' he says with a laugh. His training as a 'Miesian' modernist deeply ingrained in him the view that less is more. 'I felt, however, that the beams would add texture and softness,' he explains.

Owning a villa in Mallorca himself, David is well versed in the Iberian vernacular, but he and the wife also went shopping in Morocco, where the vivid colours and vibrant decoration provided further stimulus. Cut-and-paste pastiche, however, was certainly not the aim. 'She likes quirky, eclectic interiors and didn't want it to seem as if it all came from one source.'

Many of the family's existing furnishings, carefully accrued while they were living in London and on the Continent, were shipped across the Atlantic, but David relished the serendipity of shopping locally. 'We stuck in a thumb and pulled out some real plums. For example, we bought French cement tiles from Exquisite Surfaces, which proved exceptionally well informed and creative.' Its expertise made it simpler to make transitions underfoot an integral feature of the design, with a clever counterpoint of historic and cultural references adding depth to the new.

David set reclaimed parquet - sanded and tinted to seem as if 'it had been rescued from a Normandy chateau' - against a herringbone of terracotta tiles. Pattern, too, was a critical part of the mix. A stop at Popham Design in Marrakech unearthed a range of floor tiles featuring vintage David Hicks designs, which have now been jumbled up in a striking way in the kitchen and dining room. 'We found some tiles stuck at the back of the shop that were much older and dustier, and asked: "Is there any chance we could have these please?"' Upstairs, for the flooring in one of their son's rooms, a medley of woods have been stained in a variety of colours and laid in parquet style for motley effect.

The atonal symphony is continued outside, where a tapestry of tiling in a garden niche pays tribute to the work of David's uncle, the pioneering post-war textile designer Tibor Reich. Yet, like the house - now united in its cool and elegant spaces - the garden is a place of harmonious contrasts. At the rear, for example, a Latin-American-style garden, casual and low maintenance, counters the more formal courtyard at the front. Inside, antique finds from French brocantes and Californian flea markets sit easily beside pieces by the finest modern makers to create a look that is comfortable and stylish. It's the best of the old world and the best of the new, with nothing lost in translation.

Bentheim London: 020-7376 3427; bentheim.co.uk