F.2 Development is permitted by Class F subject to the condition that where—
(a)the hard surface would be situated on land between a wall forming the principal elevation of the dwellinghouse and a highway, and
(b)the area of ground covered by the hard surface, or the area of hard surface replaced, would exceed 5 square metres,
either the hard surface is made of porous materials, or provision is made to direct run-off water from the hard surface to a permeable or porous area or surface within the curtilage of the dwellinghouse.