CITY UNIVERSTIY OF HONG KONG
DIVISION OF BUILDING SCIENCE AND TECHNOLOGY
PROGRAMME : HD Architectural Studies
COURSE : Design Technology and Studio 1
COURSE NO. : BST 1181 (Sem.B 1999)
LECTURE 2 : INTRODUCTION TO BUILDING CONTROL
In the previous lecture you were introduced to some basic concepts about Development Control in Hong Kong - the Buildings Ordinance (BO), Outline Zoning Plans (OZP) and Lease Conditions. These controls govern the permitted use and volume of buildings that can be erected on any given piece of land in three different ways:
However, information on the restrictions on use and volume alone is not enough to see you through the design of a building. They may be adequate for doing outline schematic sketches where only the approximate size and outline of the building is needed for a preliminary setting out on the site to study the possibilities. But in designing the actual spatial layout of a building you need much more information. You need to know the requirements for the building elements, e.g. building heights, window sizes, number of exits, etc. This type of control is known as Building Control.
2.0 The Buildings Department
The Government department responsible for building control is the Buildings Department (BD) under the Building Authority (BA). Besides the Buildings Ordinance, there are a number of documents regarding building control that are issued by the BD and the Government:
Building regulations are laws of Hong Kong. They are statutory requirements which must be followed unless an exemption or modification of a regulation is applied for and approved by the BD. The COPs and PNAPs are issued to set down the standard and guidelines with regard to the compliance with the BO and its regulations. The HKPSGs list out the detailed requirements of various land uses.
The principle means of control by the BD is through an approval and consent process. Plans of new building works must be submitted to the BD to be checked to ensure that the proposed new building complies with the relevant regulations. These plans are required to be prepared and endorsed by Authorized Persons - the statutory agent between the BA and the building owner - and submitted to the BD in multiple sets and in the prescribed format together with the requisite forms.
The BD will reply by letter within the statutory period whether the plans are approved or disapproved. The statutory period is 60 days for new submissions, major revisions and major amendments, and 30 days for minor revisions and amendments. If the plans are disapproved, the BD will list on the disapproval letter which regulation(s) was broken and how it was broken. The letter will also contain comments from other Government departments such as the Lands Department, District Land Office, Highways Department, etc.
Even with all the plans approved by the BD, the building owner still cannot begin construction of the building. Approval only means that the building as shown in the submitted plans comply with the BO and regulations under the BO. This does not necessarily also means that the existing conditions on site are ready for construction to take place. After securing approval, the AP must apply for a Consent to the Commencement of Building Works from the BD before construction can begin on site. Consents can also ensure help to ensure that building works are done in the correct sequence. Sometimes, all works of a construction stage of a building must be completed and checked by the BD before the consent of the next stage will be granted. An Occupation Permit from the BD can be applied for if all works are completed according to the approved plans.
Although in theory, the works represented in the building plans approved by the BD should comply with all relevant regulations, in practice, it is not the BDs responsibility to ensure that every aspect of the building plans comply with the statutory requirements. Under "curtailed basis" checking, the BD only checks the fundamental aspects (Plot ratio and site coverage; Building projections; Open space; Means of access and escape in case of fire; Fire resistance and compartmentation; Lighting and ventilation; Sanitary provisions; Lane / street provisions; and Barrier free access). It is the APs responsibility to ensure the building design does not contravene with the Building Ordinance.
The following aspects are more relevant to your studio project and will be looked into in more detail:
2.1 Open Space
(Note: Before we go into open space requirements, it must be clarified that because of the small size of you building lots, the requirements for open space is slightly relaxed in your studio project. Therefore, except for lot 86A, which is a Class B site, you will be under-providing open space if you build up to the maximum site coverage.)
Open space requirements are specified under section 25 "Space about domestic buildings" of the Building (Planning) Regulations:
It is important to remember that this regulation only applies to DOMESTIC buildings, i.e. buildings constructed or intended for habitation. The purpose of this regulation is to ensure that there is enough open space between buildings to allow adequate natural lighting and ventilation to reach living spaces in a building. S25(1)(b) effectively states that the minimum dimension of the required open space shall not be less than 1.5m at any point. Calculations for the minimum size of the required open space is given under the Second Schedule of the B(P)R:
Class of Site Open Space Required
Class A site Not less than one-half of the roofed-over area of the building
Class B site Not less than one-third of the roofed-over area of the building
Class C site Not less than one-quarter of the roofed-over area of the building
Second Schedule: Open Space About Domestic Buildings
Other key requirements under B(P)R S25 are:
2.2 Lighting and Ventilation
Part IV of the B(P)R covers lighting and ventilation requirements under S29 to S37.
Similar to open space requirements, not every type of buildings are required to be provided with natural lighting and ventilation. Shopping arcades, for example, are not required to have windows for the purpose of provision of natural lighting and ventilation. "Prescribed windows" are windows for the satisfaction of the requirements. All such prescribed windows must face into external air as defined under S31 of the B(P)R. In terms of size, the prescribed window should also satisfy the following for provision of natural lighting and ventilation respectively:
The requirements for a window serving a room containing a soil fitment (e.g. a bathroom with a water closet) are slightly different. Both the area of the aggregate superficial glass and the openable portion of the window shall not be less than one-tenth of the area of the floor of the room. The window is required to open directly into open air, not external air, where open air is defined as a space which:
2.3 Fire Compartmentation and Separation
Part XV of the Building (Construction) Regulations and the Code of Practice for Fire Resisting Construction (FRC) covers the requirements for prevention of the spread of fire to nearby buildings. The means of prevention under the B(C)R is twofold:
By dividing a building into smaller compartments of walls and floors of a specified fire resistance period (FRP), a fire can be contained within a smaller area to prevent the fire from spreading to other parts of the building and allow adequate time for people in the building to evacuate. Table 2 in the FRC lists out the maximum compartment volume and the required FRP for various uses and Tables A to F list the minimum thickness to reach a FRP of 1hr, 2hr or 4hr, for different materials.
Apart from specifying the minimum FRP for fire compartment walls for the different uses, the FRC also sets out the guidelines for disposition of openings with respect to adjoining buildings in paragraph 7. These can be summarised as follows:
2.4 Building Height
The minimum height of storeys for a room for the purpose of an office or habitation must be at least 2.5m measured from floor to ceiling. When there are beams running across the ceiling of such rooms, the clear height measured from the floor to the underside of beams must be at least 2.3m. (B(P)R S24(1)) For such rooms with a sloping ceiling, the minimum height should be taken as the mean height of the ceiling above floor level, but in no case should any part of the room has a clear height of less than 2m.