The Building (Scotland) Regulations 2004

[F1Surface water drainageS

3.6  Every building, and hard surface within the curtilage of a building, must be designed and constructed with a surface water drainage system that will–

(a)ensure the disposal of surface water without threatening the building and the health and safety of the people in and around the building; and

(b)have facilities for the separation and removal of silt, grit and pollutants.]