Simon Miller Architects' refurbishment of this house in north London includes a new staircase that runs from the entrance hall to the newly extended loft. It is a 'folded plate' of 70mm kiln-dried French oak treads and risers, which cantilever from the walls on a concealed steel string plate.
The first floor and loft landings, together with their soffits, are made of oak boards to contrast with the maple floors used throughout the rest of the house, reinforcing the concept that the staircase and landings have been slotted into the building as a single unit.
The sloping 250mm deep x 10mm string plate is bolted to the wall with resin anchor bolts and has a series of M12 bolts welded to it. They are fitted into holes drilled in the sides of the treads and are secured with epoxy resin. The bolted connection between an upper and lower tread and the intermediate riser consists of four M10 studs welded to a 25 x 6mm steel flat that is concealed in a slot routed in the top of the upper tread.
The studs are bolted through a 25 x 3mm steel flat through a slot routed in the underside of the tread. The upper slot is filled with an anti-slip oak strip;
the lower slot is filled with a plain oak strip.
A continuous 12mm toughened glass balustrade protects the staircase; it is clamped to the treads and risers and the fixings are concealed with a 70 x 70mm oak edge strip, pre-cut from each tread and riser and refitted to the edges. The angle of slope of the top edge of the balustrade differs from the stair pitch to maintain continuity at landings and winders. An additional handrail will be fixed to the wall.