(1) Cavity-walls may be used for load-bearing purposed, subject to the conditions specified in this section.

(2) The inner and outer leaves of the shall be separated by a cavity which shall, throughout, be of a width of not less than 50 and not more than 75 millimetres, and, where the damp-proof layer does not bridge the cavity, shall, throughout extend at least 150 millimetres below damp-proof level, but in no case below finished ground-level.

(3) The inner and outer leaves of the wall shall be securely tied to each other with bonding-ties in accordance with the following paragraphs-

a) such ties shall be placed at distances apart not exceeding 1 metre horizontally and 450 millimetres vertically;

b) within 150 millimetres of the sides of every opening, there shall be one tie to every 300 millimetres of height of such opening if the leaves are not connected by a bonded jamb;

c) the ties shall be butterfly type or vertical twist type, and shall conform to S.A.B.S. 28. Metal ties for cavity walls

(4) During construction, the cavity shall be cleared regularly of mortar droppings or other debris, and provision shall be made to drain the cavity.

(5) The cavity shall be sealed at the top of the wall, and, if the wall in the storey above overhangs the wall beneath, the lower wall shall be sealed at its top by solid walling of a height of not less tha 215 millimetres and of a thickness, measured in the direction of the thickness of the wall, of not less than 215 millimetres.

(6) where the wall supports a floor on which the superimposed load exceeds 250 kilograms per square metre of floor area, the floor-loads shall be deemed to be carried entirely on one leaf of the wall, which shall be designed and constructed to carry such load.

(7) The external leaf of a load-bearing cavity-wall shall be supported by floor-slabs carried through both leaves of the wall at vertical intervals not greater than 12 metres or three storeys, whichever is the lesser; in such a case, the internal leaf of the wall below such a slab shall be designed to carry the loads coming from both leaves of the wall above such slab.