At the heart of the Bughtrig restoration is the fabulous white limestone staircase – three flights of cantilevered stairs hanging in the air as if by magic. The building developed from a simple three-bay house, one room deep, to become the seven-bay, double-depth country seat of the Ramsay family. The staircase replaces two timber stairs, both inappropriate to the enlarged building. Rationalisation of the staircase – to a central location behind the entrance hall – required absolute precision. The new stair had to fit within tight parameters in an A-listed building, and had to connect four existing floors, each floor-to-floor interval being fixed and different to the others. The task called for special measures … it became Smith & Garratt’s first foray into 3D design.
Despite appearing to hang in the air by magic, the stair is, in fact, solidly held by (i) a thickened and reinforced foundation; (ii) lug-ends of each step built into semi-circular walls of engineering brick; (iii) a stainless steel pin between each step, hidden inside the flying end; (iv) three half-landings, each made in three sections with concealed steel flitches welded to posts within the masonry either side of the rear-facing windows, behind the masonry; and (v) steel brackets at each landing, meeting the top of each flight. All of this complexity was precisely designed in advance, in 3D. The stones were cut using a computer-driven CNC cutter and the steel was adapted and precision-welded on site.
The new stair provides a fire escape from all upper floors. The stairs and stairwell are entirely non-combustible, and the stairwell is protected by automatic smoke curtains. Detailed design, listed building consent, building standards approval and project management were delivered by Smith & Garratt. The project was Commended at RICS Awards Scotland 2013 (building conservation category).
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