Escada House.

The house stood empty for twenty years on a steep plot above the river, its concrete frame sound but its rooms dark and divided. Only the frame, the foundations and the view were worth keeping.

The slope set every rule: four floors stepping down from the street to the garden, and one stair to tie them together. There was room for one idea, and it had to be the stair.

A continuous stair of white lime plaster folds around a light well from the street door to the garden, its balustrade a solid curving wall that thickens into a seat on every landing: a reading nook, a desk, a window bench.

We drew it at 1:5 for months, and built a full-height mock-up of one flight in the contractor's yard before a single tread was cast.

Outside, each floor is wrapped in a curved balcony of white render, 1.8 metres deep at its widest, that shades the glass in summer and lets the low winter sun reach far into the rooms. From every bedroom, the balconies frame the river and the sea beyond.

A rooflight the full width of the light well brings daylight eleven metres down. The plaster balustrade catches it and passes it on, so the dining table on the garden floor has sun on it at midday.

Inside, everything is white lime, pale oak or honed limestone: three materials chosen to age together. Bathrooms are lined floor to ceiling in stone, with freestanding baths set beneath the windows.

The house is now home to a cellist and her daughter. The stair, she tells us, has the best acoustics in the building.