(1) Except as provided for in subsection (4) of section 3, all foundation-walls shall have horizontal damp-proof courses set not less than 150 millimetres above the finished ground-level and also on the underside of any timber in the ground-floor construction which is in contact with such walls, and such timber shall be treated with preservatives and supported as stipulated in the requirements of Chapter 3.

(2) In the case of a floor in contact with the ground, the horizontal damp-proof course in the enclosing walls shall be placed either in the first course above the top level of the floor and carried down the inner face of the walls to below floor-level, or in the first course below the top of the floor, in which case it shall be carried up the inner face of the walls to above floor-level.

(3) Where an internal wall rests on a suitably strengthened or adequately supported floor in contact with the ground and a horizontal damp-proof course under such floor is not required by the local authority, in terms of the powers conferred on it by subsection (2) of section 8, such a wall shall be built on a damp-proof course laid on the floor.