(1) Empirically constructed brick bearing-walls shall have a thickness of not less than 100 millimetres, and shall be constructed to comply with the requirements of the following subsections.

(2) external walls of a thickness of 100 millimetres shall be permitted to be constructed for use in any veranda, loggia, garage to a dwelling-house, greenhouse, servant’s quarters to a dwelling-house, tool-shed, potting shed, cycle-shed, aviary, poultry-house or summer-house, or a dwelling-house in an area designated by the local authority:

Provided that-

a) every such wall shall not exceed 2,5 metres in total height;

b) in the case of multi-storey buildings, the length of every such wall shall not exceed 3,4 metres by a pier or piers, 215 millimetres square in total horizontal cross-section, bonded into it, in which case the total length of every such wall may be 10,63 metres;

c) in the case of single-storey buildings, the length of every such wall shall not exceed 4 metres, unless it is divided into panels of no greater length than 4 metres by a pier or piers, 215 millimetres square in total horizontal cross-section bonded into it, in which case the total length of every such wall may be 8 metres;

d) except in the case of a veranda or loggia-

i) the building shall be wholly detached from any other building; and

ii) the building shall be approved designed; and

iii) the volume of the building shall not exceed 60 cubic metres except a dwelling-house in an area designated by the local authority;

e) the roof resting on such walls be so constructed that no load other than the mass of the roof and the wind force on it shall be transmitted by the roof to the wall;

f) the highest point of the roof resting on such walls shall be not more than 1,5 metres above the top of any of them;

g) except in the case of the walls constructed of brick of a compressive strength of not less than 15 megapascals and water absorption not exceeding 12 per centum laid in class B mortar, as defined in subsection (3) of section 13, every such wall of every habitable room shall be plastered externally with plaster complying with the requirements of class D mortar in section 13 to a thickness of class D mortar in section 13 to a thickness of not less than 10 millimetres.

(3) External walls of 100 millimetres in thickness shall be permitted to be constructed for use in a structure above the general level of a flat roof of a building and need not be subject to the limitations set out i subsection (2) if-

a) such structure is not used or adapted to be used as a habitable room or as workroom or office; and

b) the height of the walls does not exceed 2,4 metres, measured to the it top from the level of the flat roof adjacent; and

c) the length of the walls does not exceed 3 metres.

(4) Internal walls of 100 millimetres effective thickness shall be constructed in accordance with table XI, and shall-

a) be of brick with a compressive strength of not less than 7 megapascals or such other strength as the local authority shall determine; and

b) be laid in class B mortar; and

c) not be used in storeys other than the topmost two storeys of a building; and

d) in a single-storey building or the topmost storey of a building, be at least moderately restrained at the top.