Building Construction Handbook, Eighth Edition

Application † a straight flight for access to a domestic loft

conversion only. This can provide one habitable room, plus a

bathroom or WC. The WC must not be the only WC in the dwelling.

Practical issues † an economic use of space, achieved by a very

steep pitch of about 60°and opposing overlapping treads.

Safety † pitch and tread profile differ considerably from other

stairs, but they are acceptable to Building Regulations by virtue of

``familiarity and regular use'' by the building occupants.

Additional features are:

* a non-slip tread surface.

* handrails to both sides.

* minimum going 220 mm.

* maximum rise 220 mm.

*(2+ rise) + (going) between 550 and 700 mm.

* a stair used by children under 5 years old, must have the tread

voids barred to leave a gap not greater than 100 mm.

Ref. Building Regulations, Approved Document K1: Stairs, ladders

and ramps: Section 1.29

Alternating Tread Stairs