Loft story: Design of a luminous loft under a Victorian roof revolves around a new staircase and skilfully manipulates available sources of light.

Azman Owen's tough industrially inspired architecture is infused by a quirky imagination; and their schemes contain details that challenge social conventions of privacy. In this, the practice has no doubt been encouraged by the clients' eccentricities. A house for fashion luminary Isabella Blow has a glass bathroom and bath, open to the sky and almost to neighbouring scrutiny; and the linear showroom, full of heavy metal, for British fashion designer Alexander McQueen (AR February 2000), has a diaphanous changing cubicle of electrotropic glass that, to the timid, feels dangerously public.

Much the same epithet can be used to describe the glass bottomed bath suspended over the kitchen in a new scheme for a loft flat in north London -- though the official explanation, which is visibly true, is that the device allows light into an obscure part of the space.

The flat occupies a single volume at the top of a Victorian school and under original roof trusses. It measures 9x7m and houses two mezzanine floors once connected by a spiral staircase. Apart from rooflights across the west side of the roof, there was only one other window

The spiral staircase and mezzanines were originally supported by randomly placed steel columns. To liberate space, the architects removed the columns and transferred loads to existing masonry walls and roof trusses. The central core of this scheme, constituting a strong vertical element, then became a new staircase with straight flights which links the three levels in elegant fashion. With steps and risers of mild steel, the stair is contained by a great vertical curtain of steel uprights and rods on one side, and wooden shelving on the other.

The upper mezzanine was made into a sleeping gallery and a glass panel inserted into the west side of the floor to allow daylight to filter down. On the mezzanine below, which takes advantage of the one window, the architects created the luminous bathroom with the two glass floor panels, one of which became the base of the bath. The curious arrangement should not distract attention from the ingenuity of this scheme.