The Welfare of Farmed Animals (England) Regulations 2007

2.  All systems must be equipped in such a way that all laying hens have—

(a) linear feeders providing at least 10cm per bird or circular feeders providing at least 4cm per bird;

(b) continuous drinking troughs providing at least 2.5 cm per hen or circular drinking troughs providing at least 1 cm per hen;

(c) at least one nest for every seven hens and, if group nests are used, there must be at least 1 m² of nest space for a maximum of 120 hens;

(d) perches without sharp edges and providing at least 15 cm per hen, which must not be mounted above the litter, and the horizontal distance between perches must be at least 30 cm and the horizontal distance between the perch and the wall must be at least 20 cm; and

(e) at least 250 cm² of littered area per hen, the litter occupying at least one third of the ground surface.