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BUILDING (PLANNING) REGULATIONS, 1956
Part NL--Heights, Folumes and Open Spaces.
6. The provisiona concerning heights of buildings in the former Ordinance (sections 77 and 78) controlled the vertical height of the main wall and by means of an angle of set-back the overall height of the building. The effect of this was to establish a rigid building profile which, to a very great extent, dictated the design of every building. Regulation 17 permits the main vertical height of the front main wall to be twice The width of the street on which it abutts as against the 13 times the width of the street permitted under the former Ordinance. Above this height the main walls are required to be set back within an angle of 76" with the horizontul (regulation 18) as against 68* permitted under the former Ordinance, which also provided that the total height of the building was limited to twice the width of the street. (In lots leased post 1003 the restrictions were greater). The provisions of regulations 17 and 18 are the outcome of consideration being given to Hong Kong's geographical position, the resulting meridan altitude of the sun and the hours of sunshine throughout the year. The requirements as to the set- back of 7G* is intemled to safeguard natural lighting to streets and, will; a vertical height of twice the width of the street, the set-back line if projected downwards meets the centre of the street. Subject to these limitations the height of a building is restricted only by the permitted volume, which is calculated by multiplying a factor (F) by the width of the street and by the area of the site. (Regulation 20). In the case of domestic buildings this factor (F) is worked out for & terrace house, this usually being the least advantageously sited for providing light and ventilation. The factor is increased where the buikling is on a corner site, and increased again where it abutts on three or more atreela.
7. As well as the limitation on heights of main walls and on volumes, every domestic building is required to be provided with open space within the lot of auch building. (Regulation 22). It is not ground space ao inuch as air space which is intended to be provided by this regulation. Thus, since the space must be provided at a level of 0" below the lowermost storey of the domestic building, a building could cover the whole of the site at ground level with the premises of a non- domestic nature and become a domestic building at its second or thinl storey, provided it complied with this requirement as to open space. The proviso to regulation 22 is included to enable the Building Authority to deal with any special circumstances which may arise in the application of cases 2 and 3 in Table II which permit reduced amounts of open space,
B. Within the building, lower heights of ceilings are permitted under regulation 21 than those permitted under sections 29 to 31 of the former Ordinance. The present heights have been determined after ron- sidering the information, with special reference to Hong Kong, received from the Building Research Station and the Department of Scientific and Industrial Research, which goes to show that provided there is adequate ventilation and that ceilings and roofs are properly constructed, lower ceiling heights will not adversely affect the health of the occupant
Part IV-Lighting and Ventilation.
The provisions in this Part expand considerably those contained in sections 63-08 of the former Ordinance. They are concerned with buildings used as offices or for habitation, with special provisions for kitchens and water-closets (regulations 31 and 82). Under regulation 26. every room in such a building is required to be lighted and ventilated by
BUILDING (PLANNING) REGULATIONS, 1956
a window opening into the external air, which is defined in regulation 2 and, by that definition, must be opened to the sky and have a horizontal area of at least 120 square feet. The regulation goes on to prescribe
En detail the specifications of a window which will be considered as adequate to give this lighting and ventilation; for example, paragraph (3) deals with the case of a window situated in a well of a building and, since this affects primarily the light, the provision is more stringent in the case of buildings used for habitation than in the case of an office building.
10. In certain cases the Building Authority may, by virtue of regula- tion 20, permit mechanical ventilation as an alternative. A building which is erected in accordance with these regulations is thereafter protected by regulation 33 which prohibits any other building being erected in much manner as to reduce the minimum quantity of light and air required by the first building.
Part -Staircases and Fire Escapes.
11. The provisions of this Part which replace and expand sections 33 and 35 of the former Ordinance, are designed to ensure that occupants may escape safely from buildings in case of fire. Where a building exceeds two storeys the main staircase is required to be constructed for its whole height of materials capable of resisting the action of fire for one hour: and where it exceeds four storeys its main staircase is required to give access to the roof unless a secondary staircase or fire escape is provided. (Regulations 34 and 36). Where the building exceeds six storeys, regula- tion 87 requires the provision of an alternative means of escape in addi- tion to the main staircase. Under the former Ordinance this additional means of escape was required, in any building with a door level at a haight of more than 35 feet; this easing of restrictions is explained partly by the more incombustible materials used in buildings to-day, and by the greater heights which can be reached by ladders on miodem fire appliances.
12. Regulation 36 provides that in any building intended for separate occopation by more than two tenants, the cammon staircase and landings shall be constructed to resist the action of fire for more than one hour. Regulation 39 provides that in every building intended for habitation or as a school, or as a place of public assembly, there shall be no place more than 80 feet from the staircase or other normal exit. Further provisions concerning the fire resisting qualities of materials used in the construction of buildings will be found in Part XIII of the Building (Construction) Regulations.
Part VI-Domestic Buildings.
13. In this Part are gathered together three subject matters particularly relevant to domestic buildings-kitebens, retaining walls and dangerous trades; there are also provisions to be applied to the special class of domestic building known as tenement houses. "Regulation 41, which deals with kitchens in domestic buildings generally, replaces section 54 of the former Ordinance. Regulations 43 and 44 replace and expand the provisions of section 13 of the former Ordinance, and permit retaining walla less than 15 feet high to form part of domestic buildings subject to certain specified requirements. It is hoped that the provisions of these regulations will tend to eliminate waste in the use of land in sloping sites, give architects greater freedom in design and possibly reduce building costs. Regulation 45 prohibits the use for domestic purposes of a building in which are carried on any of the dangerous trades there specified; the Building Authority is, however, permitted to grant exemp tion and prescribe auch requirements as he sees it.