PROGRAMME : HD Architectural Studies

COURSE                 : Design Technology and Studio 1

COURSE NO.          : BST 1181 (Sem.B 1999)



1.0 Introduction

Before a developer decides on investing in developing a piece of land, there are a lot of factors he must consider in order to ensure that he is about to make a smart investment. Developers would not invest millions and millions of dollars into buying a building site not knowing what kind of development can be built on it. Considerable time and effort would be spent to investigate important information about the site: What type of buildings can be built on the site? What is the total floor area permitted on the site? How assessable is the site? Any public transportation or major highways nearby? These factors determine the value of the future property to be erected on the site. This research into the background information of the site and the subsequent determination of the size and nature of the developments possible on this site is called a feasibility study.


The two factors the developers are most concerned with are without doubt the size (how much floor area) and the use (what function(s): residential, commercial, office, etc.) that is permitted on the target site - the development potential of the site. However, developers cannot simply build whatever they like on a site in terms of size and use. There are a number of means of statutory control which determine the development potential of any site in Hong Kong. With respect to size, most of these controls limit the maximum permissible floor area of a site.



2.0 Types of Floor Area


Different parties in the construction industry are concerned with different types of floor areas:


Gross Floor Area (GFA)

Usable Floor Area (UFA)

Saleable Area

Some of these floor areas have specific definition under the Building Ordinance and other statutory regulations or legislation. In some cases, the same term (e.g. gross floor area) may have slightly different meanings when viewed under different statutory bodies (e.g. the Buildings Department and the Lands Department).


Before the Consumer Council released a guideline on how to determine what constitutes the floor area of a flat the buyer is paying for, there are more ways of calculating the size and efficiency of a residential flat than you can imagine. Taken literally, efficiency is defined as the percentage of a flat that is usable. This can be simply calculated as the portion of the floor area of the flat which is useful divided by the overall floor area of the flat. However, some dishonest developers had in the past included various miscellaneous areas - bay windows, proportionated club house area, flat roofs, etc - into the usable portion in order to attract potential buyers. There were even cases where developers quote that the efficiency of their flats is over 100%!


Following the release of the Consumer Council guideline, all sales booklets must clearly state the various types of floor area and list each one of them separately so that the consumers have a better idea of what they are paying for.


2.1 Gross Floor Area (GFA)

GFA is important because almost all statutory control limit the size of a building on a site in terms of the maximum permitted GFA of the development on a it. Under the Building Ordinance, GFA is defined as:


Building (Planning) Regulation 23(3)(a):

"… the gross floor area of a building shall be the area contained within the external walls of the building measured at each floor level (including any floor below the level of the ground) together with the area of each balcony in the building …"


Building (Planning) Regulation 23(3)(b):

"… in determining the gross floor area … the Building Authority may disregard any floor space that he is satisfied is constructed or intended to be used solely for parking motor vehicles, loading or unloading of motor vehicles or occupied solely by machinery or equipment for any lift, air-conditioning or heating system or any similar service." 










Gross Floor Area (GFA)


One must be very careful when calculating the GFA for submission purposes because of differences in interpretation. For example, the term GFA under the Building Ordinance may include areas of functions which are not included in GFA calculations under Lease and vice versa. Hence, the GFA under Building Ordinance and under Lease may be different even for the very same building. GFA is the area usually quoted in property transactions in Hong Kong.


2.2 Usable Floor Area (UFA)

UFA has significance mainly under the Building Ordinance in the calculation of number of persons in a building for provision of sanitary fittings and escape routes. Under the Building Ordinance, UFA is defined as:


Building (Planning) Regulation 2(1):

"… means any floor space other than staircases, staircase halls, lift landings, the space used in providing water-closet fitments, urinals and lavatory basins and the space occupied by machinery for any lift, air-conditioning system or similar service."











Usable Floor Area (UFA)


2.3 Saleable Area (SA)

SA is the actual floor area used solely by the tenants excluding all common areas. This is the area of the unit itself including the whole thickness of all walls between the unit’s space and common areas and half of the thickness of all walls between two units. The Consumer Council now requires the SA of all units to be listed in sales brochures and other information provided by the developers. The efficiency of a building is calculated as the total SA of the building divided by the total GFA of the building:















Saleable Area (SA)


2.4 GFA of a Unit

Despite the requirement of a clear listing of the SA of a unit in sales information, the SA is still not adapted as the measure of size on which a property transaction is based on. The established practice is that properties are bought and sold in terms of their GFA and all prices per square are calculated in relation to the GFA and not the SA. There is, however, no definite way of calculating the GFA of a unit. The most common way is to proportionally distribute the floor area of the common areas to each unit according to its size. The GFA of a unit can be calculated as:


            GFA (UNIT) = SALEABLE AREA (UNIT)   divided by   EFFICIENCY



3.0 Development Control


The Hong Kong Government has three ways of controlling the size of new buildings:


Building Ordinance

Outline Zoning Plan

Lease Control

Each of the above may control the size of a new building in terms of the maximum permitted GFA, plot ratio, site coverage, building height, or a combination of the above, where:


Plot Ratio = The multiplication factor which, when applied to the gross site area, determines the total permitted developable area (Site Area x Plot Ratio = Maximum Permitted GFA).

Site Coverage = The percentage of the site area covered by building(s)


3.1 Building Ordinance

Under PART III of the Building (Planning) Regulations, the permitted plot ratio and site coverage of any given is related to the number of sides of the site abutting on streets that are more than 4.5m wide. They are classified into Class A, B or C sites if they abut on one, two or three 4.5m streets respectively. The FIRST SCHEDULE listed in table form the relationship between the maximum permitted site coverage and plot ratio to building height and class of site for domestic buildings (buildings constructed or intended for habitation) and non-domestic buildings.


3.2 Outline Zoning Plan (OZP)

Under the Town Planning Ordinance, OZPs are prepared under the direction of the Town Planning Board. The OZPs show the general land use pattern of a region in which areas are zoned for residential, commercial, industrial, GIC, etc. Attached to each plan is a set of notes. Apart from listing the uses that are always permitted under each zoning and the uses that require an application to be approved by the Town Planning Board, the notes also list plot ratio and/or site coverage restrictions specific to each zone or area. The OZPs represent control exercised over a specific region while the Building Ordinance controls all buildings in general terms.


3.3 Lease Control

Even more specific are development conditions imposed by the Hong Kong Government through the lease of the site. Apart from limitations on the use plot ratio, site coverage, building height, etc of any new buildings, the lease conditions may also contain detailed requirements on non-building areas, building set-back, carpark provisions, and sometimes even the "style" of the new buildings.


Often, the resulting maximum permitted gross floor area calculated under the above government control may be different from one another. It is essential that the building satisfies ALL of the above requirements.