Repositioning the main staircase may both free wasted space in the house and result in a safer design. Many staircases in pre-1940 properties were badly designed with an uneven pitch, unequal treads and narrow and steep winders. As such they have caused innumerable accidents.
A repositioned staircase must comply with building regulations. These require:
1 An equal rise of not more than 2-2 cm and going of not less than 2.2 cm (exact equivalent: 8-a- in.) for every step and landing between consecutive floors.
2 A headroom of not less than 2 m (6 ft 7 in.) measured vertically above the pitch line and a clearance of not less than 1.5 m (4 ft 11 in.) measured at right angles to the pitch line.
3 A pitch to the staircase of not more than 42 deg.
4 Twice the rise plus the going in centimetres must not be less than 5.5 cm and not more than 7.0 cm (equivalents: 1 ft 91 in. and 2 ft 31 in.). This is to ensure that steps are safe and easy to ascend or descend. If space is at a premium, tapered steps within the staircase flights, known as winders, are permitted, subject to particular requirements.
6 Every staircase must be guarded on each side and the minimum height of the hand-rail above the pitch line of the staircase must not be less than 8.4 cm (or 2 ft 9 in.).
7 The side of any landing or similar space forming part of a stairway or directly overlooking a stairwell must also be guarded by a wall, securely fixed screen or balustrade of 9.0 cm minimum height (equivalent to 2 ft 11 in.).
8 If the new staircase is designed on the open-tread principle, one tread must overlap the back edge of the tread below by not less than 15 mm (1 1/4 in.).
Modern glues have simplified staircase construction. For staircases not exceeding 3 in. (or 9.0 cm) in width, 1 ¼ in (3 cm) treads and 1 in. (2.5 cm) risers are normally adequate.
The treads and risers are carried on inclined timbers known as strings. The normal fixing between the strings and treads is by a.4 in. (19 mm) deep groove and timber dowels, the dowels restraining the strings from bowing outwards. The treads and risers should be glued in position with a resin gap-filling glue.
Ready-made staircases or staircase kits can be bought for assembly.