1.1     Objectives and Functions of Residential Density Guidelines

1.1.1   Residential density is a quantitative measure of the intensity with which land is occupied by either development or population. Control of residential density is a fundamental component of effective land use planning, as the relative distribution of population has major implications for the provision of public facilities, such as transport, utilities and social infrastructure. 

1.1.2   The main objectives of density policy are:

              (a)    to promote an acceptable standard of environment and amenity for the occupants of residential areas;

              (b)    to ensure an appropriate balance between the residential population of an area and the capacity of the existing or planned facilities and infrastructure required to service it;

              (c)    to maintain an efficient intensity of land use in the context of competing demands on a limited supply of developable land;

              (d)    to maintain safe levels of development and population in areas where there may be potential risks due to adverse geotechnical conditions, neighbouring hazardous installations, etc.; 

              (e)    to provide for a variety of urban form for urban design reasons and to satisfy the demands of different market sectors; and

              (f)    particularly in rural areas, to ensure development is of an appropriate scale in relation to its landscape setting.

1.1.3   Residential density guidelines promote these objectives by establishing a coherent framework of density standards for application to different types of area. These standards are used to guide planning at all levels from strategic planning to development control and they are applicable to both public and private housing. They should, however, be used flexibly to take account of variable local circumstances.

1.1.4   The primary purpose of the guidelines is to enable planners to make reliable estimates of the population capacities of areas zoned for residential development, or conversely to estimate the land area required to accommodate a given population. Such estimates are required to ensure that adequate infrastructure and services are planned to satisfy the needs of the future population and to indicate where densities may need to be restricted on a site or area basis to achieve this.

 1.2      General Residential Density Principles

1.2.1   In applying residential development densities, there are a number of general principles which need to be considered coherently with a view to achieving integration of land use, transport, environmental and infrastructural planning. Through such integrated planning, residential developments of different densities can be planned to achieve the most efficient and functional disposition and economies of scale in terms of social, transport and infrastructural provisions while meeting environmental objectives.

1.2.2   The relevant principles guiding the residential densities with the above integrated approach are:

                (a)  There should be a hierarchy of residential densities to meet market needs for a diversity of housing types;

                (b)  Residential densities should be commensurate with what the existing and planned infrastructural and environmental capacities can cope with;

                (c)  Developments should be placed in such a way to encourage public transport and reduce the travel demand; and as such, higher density residential developments should be located near rail stations and major public transport interchanges wherever possible to capitalize development opportunities and to reduce reliance on road-based vehicular travel;

                (d)  There could be a decreasing gradation of residential development densities from the distances to the rail stations and public transport interchanges;

                (e)  Higher density residential developments outside major transport corridors or the catchment areas of a rail station could be considered where there will be adequate feeder services from the rail stations and public transport interchanges;

                ( f ) As putting higher density residential developments near high capacity transport node would imply more sensitive receivers being subject to environmental impact, careful consideration should be given to environmental planning to ensure meeting of environmental objectives with incorporation of environmental mitigation measures where appropriate;

                (g)  To avoid monotonous urban form and achieve a more interesting townscape, residential developments at different levels of density could be considered; and

                (h)  It would be more compatible to adopt a low density for residential developments which may be located close to environmentally sensitive areas e.g. wetland, conservation areas, country parks and Sites of Special Scientific Interest in order to conserve these areas and avoid human disturbance impact on them as far as possible.

1.3      Administrative Context 

1.3.1   The administrative context for residential density controls in Hong Kong is mixed, being based partly on statutory powers and partly on administrative measures. The Buildings Ordinance, including its associated Building (Planning) Regulations (B(P)R), is the only statute which explicitly sets density limits and provides for their enforcement. The First Schedule to the B(P)R specifies the maximum plot ratios and site coverage permitted for domestic and non-domestic buildings in relation to building height.

1.3.2   In addition, under the Town Planning Ordinance, enforceable plot ratio controls can be imposed through the notation and Notes on Outline Zoning Plans.

1.3.3   Other density measures, which seek to restrict densities to below the statutory B(P)R maximum, are administrative in origin and can be incorporated in leases or reflected in OZPs for enforcement when needed. These include the HKPSG residential density guidelines and the Special Control Area provisions. Special Control Areas are designated in order to preserve areas with a special character or amenity or because of limitations in transport capacity.   

    2.1  The density of development in public and private residential areas in Hong Kong is guided by way of plot ratio. Plot ratio is defined as the ratio between the gross floor area (GFA as defined under B(P)R) of a building and the area of the site on which it is erected (the Net Site Area). The site area definitions are shown in Figure 1. Plot ratio governs the amount of GFA in buildings but affects population density only indirectly due to the interplay of other factors like, flat size and person per flat ratio.

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Figure 1  Site Area Definitions 

 2.2    The key functions of residential density guidelines are therefore twofold:

         (i)    to set out the plot ratio controls relevant to different categories of development; and

         (ii)    to show how these can be converted into the likely levels of population they may generate.

 3.1      Enforcement of Building Development Intensity

3.1.1     The ultimate maximum domestic plot ratios permissible in Hong Kong are set by First Schedule of the B(P)R. Restrictions below this level can only be enforced through:

                    (a)    statutory controls incorporated in Outline Zoning Plans or Rural Outline Zoning Plans

                    (b)    Airport Height Restrictions (indirectly), 

                    (c)    conditions imposed on development under new or modified land leases, or 

                    (d)    planning permissions granted under Section 16 of the Town Planning Ordinance.

3.1.2     Building density guidelines for different types of area, under the HKPSG or the Special Control Area provisions, can therefore only be implemented where one or other of these circumstances applies. It is therefore recommended that the maximum permissible plot ratios set out in these guidelines should be incorporated in statutory Outline Zoning Plans wherever necessary and possible.

  3.2    Metroplan Area

3.2.1     The Metroplan Area comprises Hong Kong Island, Kowloon and New Kowloon and the Districts of Tsuen Wan and Kwai Tsing. Metroplan establishes the following density principles for these areas:

                    (a)    within acceptable environmental limits, to maximise the intensity of people and jobs close to high capacity transport systems (particularly rail);

                    (b)    conversely, to limit densities in areas not well served by high capacity transport systems;

                    (c)    wherever possible, to reduce densities in highly congested districts which are experiencing widespread environmental and operational problem; and

                    (d)    to limit densities in areas where the visual impact of development will be the prime concern.

3.2.2    The Metroplan area is divided into three Residential Density Zones: R1, R2 and R3 (See Figure 2).

• Residential Zone 1 covers the highest density of residential development and applies to districts well served by high capacity public transport systems such as rail station or other major transport interchange. The buildings often incorporate a significant component of commercial floorspace on the lower one to three floors.

• Residential Zone 2 covers development at a medium density and applies in locations less well served by high capacity public transport systems. There is usually no commercial floorspace component.

• Residential Zone 3 covers the lowest density of residential development and applies to districts with very limited public transport capacity or subject to special constraints for urban design, traffic or environmental reasons.

3.2.3     The maximum domestic plot ratios permissible in these zones are set out in Table 1.

 Residential Zone 1

3.2.4   Within the existing built-up area, the plot ratios permitted on redevelopment of existing buildings in Residential Zone 1 vary between the major geographical areas. First Schedule of the B(P)R currently applies on Hong Kong Island while in Kowloon, the maximum domestic plot ratio is further restricted to 7.5 based on the recommendations of the Kowloon Density Study (KDS) Review. This maximum domestic plot ratio is implemented through the relevant Outline Zoning Plans. Tsuen Wan and Kwai Tsing are governed by the plot ratios for First Generation New Towns. Site Class is a relevant factor in determining permissible plot ratio under First Schedule of the B(P)R. Where a residential building also contains a non-domestic element, the maximum permissible domestic plot ratio may be further restricted, according to the provisions of the B(P)R composite building formula. 

3.2.5   In new development areas which are not yet covered by statutory plans, including new reclamations and other newly formed areas, the maximum domestic plot ratio is 6.5. This plot ratio is lower than the statutory limit set by the B(P)R, in order to promote one of the key objectives of Metroplan, to bring about improvements in living conditions in the urban areas by reducing densities. Any non-domestic plot ratio component may be in addition to the domestic plot ratio of 6.5, up to the maximum permitted by the B(P)R composite building formula or those of the Outline Zoning Plans.

3.2.6   In Comprehensive Development Areas, the maximum domestic plot ratio will normally be 6.5 but higher plot ratios may be justified according to local circumstances where infrastructure capacity permits.

 Residential Zones 2 and 3

3.2.7   Within the existing built-up area, the limitations on plot ratio for Residential Zones 2 and 3 set out in Table 1 can only be enforced through lease conditions and planning conditions, except where they are incorporated in the Outline Zoning Plans.

3.2.8   In new development areas, the maximum domestic plot ratios for Zones 2 and 3 are set at 5.0 and 3.0 respectively.

3.3     New Towns

3.3.1   The New Towns are also divided into three Residential Density Zones: R1, R2 and R3, on the same basis as those in the Metroplan Area. In addition, a very low density zone, R4, may be designated where justified by severe geotechnical / infrastructure constraints or compatibility with the adjacent rural low density developments. The maximum domestic plot ratios permissible in these zones are set out in Table 2.

3.3.2   The new towns programme was designed to encourage the movement of population out of the congested Main Urban Areas by offering prospective residents a substantially better living environment. With the introduction of lower densities for new development areas in the Metroplan area, similar reductions may be called for in the New Towns. However, since most of the New Towns have already been comprehensively planned and developed with a maximum R1 domestic plot ratio of 8 (with commercial plot ratio determined according to the B(P)R composite building formula), there is little need for modification. A domestic plot ratio of 8 should only be permitted where there are no infrastructure constraints, e.g. close to high capacity transport systems. Elsewhere, the plot ratio should be determined according to local circumstances.

3.3.3   The maximum permitted plot ratios for Residential Zones 2 and 3 are 5.0 and 3.0, as in the Metroplan area.

3.4      Rural Areas

3.4.1   In the rural areas, densities need to be much lower than those in the urban areas, partly because of the limited capacity of transport, utility and social infrastructure but in many cases also because of the need to protect fine natural landscape from undesirable urban encroachment.

3.4.2   Six Rural Residential Density Zones cover those parts of the Rural Areas which may be designated as suitable for development: RR1 to RR5 and Village. Each relates broadly but not necessarily exclusively to a particular type of built form, and guidelines are given in Table 3 for both plot ratio and typical number of domestic storeys.

• Rural Residential Density Zone 1 (RR1) relates to a medium rise residential block with up to 12 floors including at most two commercial lower floors. It is the highest density appropriate to non-urban areas, applicable in the commercial centres of Rural Townships such as: Sai Kung, Mui Wo, and Tai O. (Maximum PR 3.6)

• Rural Residential Density Zone 2 (RR2) relates to a low-rise residential block with up to 6 floors and no commercial elements. It is applicable to areas within Rural Townships lying outside the commercial centre, and in other significant rural development areas served by medium capacity public transport, such as light rail systems. (Maximum PR 2.1)

• Rural Residential Density Zone 3 (RR3) relates to terraced housing or flats on up to 3 residential floors. These may be in peripheral parts of Rural Townships or other rural development areas, or in locations away from existing settlements but with adequate infrastructure and no major landscape or environmental constraints. (Maximum PR 0.75 over the Development Site Area)

• Rural Residential Density Zone 4 (RR4) relates to detached or semi-detached houses on up to 3 storeys (including carports), residential floors, in similar locations to RR3 but where development intensity is restricted by infrastructure or landscape constraints. (Maximum PR 0.4 over the Development Site Area)

• Rural Residential Density Zone 5 (RR5) relates to small detached houses of up to 2 residential floors, permitted as replacements for temporary structures in areas requiring upgrading. (Maximum PR 0.2 over the Development Site Area)

• Village Density Zone relates to New Territories Exempted Houses, which are permitted within the defined envelope of recognised traditional villages. (Maximum PR 3, i.e. 3 floors on 100% site coverage on a site area of 65.03 m²)

3.4.3   It should be noted that the plot ratios for RR3, RR4 and RR5 are calculated on the total available site, including roads and open space, to allow for the variable circumstances of rural sites and topography. Plot ratios for RR1 and RR2 relate to the Net Site Area (see Figure 1).

  3.5    Plot Ratio Ranges

3.5.1   The maximum plot ratios set out in Tables 1, 2 and 3 are targets to be aimed for. However, where there are significant constraints on development capacity (such as transport or infrastructure limitations, or environmental, topographical or geotechnical conditions), or special design considerations, a maximum plot ratio lower than this target may be applied. The range of acceptable plot ratios, however, should not extend below the maximum plot ratio for the next lower density zone. Where there are severe constraints on density, a density zone with a more appropriate plot ratio range should be selected for the site.

  3.6    Plot Ratio, Building Height and Site Coverage

3.6.1   The maximum permitted site coverage and resulting maximum plot ratio for domestic buildings of different heights in R1 zones are specified in First Schedule of B(P)R and shown in Table 4. In existing development areas within the Metroplan area subject to old land leases, these vary according to Site Class, i.e. the number of streets onto which a site fronts. In new development areas subject to new land grants, the maximum plot ratios stipulated under First Schedule of B(P)R may not always be achievable due to such reasons as infrastructure constraints, compatibility with adjoining development, environmental considerations and physical character of the site. A lower plot ratio may be imposed according to  Tables 1, 2 and 3 through the Outline Zoning Plans or land leases.

3.6.2   Table 5 shows how maximum domestic plot ratio varies with number of domestic floors in R2 and R3 zones. Site Class is not a relevant consideration. Maximum domestic plot ratio is achievable with buildings of 17 and 15 floors or higher, for R2 and R3 respectively.   

 4.1    Function and Estimation of Population Density

4.1.1   The function of residential population density guidelines is to convert building density in terms of plot ratio into the population that is likely to be accommodated on a site. This may be required for three purposes:

(i)   to estimate the population capacity of a site area at a given plot ratio;

(ii)  to estimate the site area required to accommodate a given population at a given plot ratio; and

(iii) to estimate the plot ratio required for a given population to be accommodated on a given site  area. 

4.1.2    Estimates of these kinds are mainly required at two different stages in the planning process:

(a) Strategic and district planning

4.1.3    At this stage, broad assessments of population or land area are required and little definite or site specific data is available. The main tasks are:

• making initial forecasts of the population capacity of potential development areas or sites (for example in Territorial Development Strategy Study), preparing development briefs, assessing infrastructure demand etc.

• estimating the area of land required to be released to accommodate a projected future population.

(b) Site planning

4.1.4   This is undertaken when more detailed and site-specific data is available. The purpose is to select a suitable plot ratio and to estimate site capacity for the preparation of development briefs or for vetting private sector proposals.

4.1.5   Different forms of density guidelines are required to meet the needs of these two stages in the planning process.

4.1.6   In practical terms, residential population density guidelines are only applicable where there is the likelihood of relatively large sites or areas being developed at a specified building density, i.e. new development areas or Comprehensive Development Areas. They cannot be used effectively to assess population capacities resulting from the piecemeal redevelopment of existing built-up areas.

Factors affecting population capacity of a site

4.1.7   The population capacity of a site for residential development depends on:

                    (a)    the developable area of the site or Development Site Area (DSA) (i.e. the Gross Site Area excluding slopes, infrastructure reserves, etc.)

                    (b)    the area of the site which has to be devoted to ancillary facilities such as roads, open space and G/IC facilities required to serve the population.

                    (c)    the permitted plot ratio to be applied to the remaining Net Site Area (NSA).

                    (d)    the occupancy rate of domestic GFA in m² per person, which is obtained by dividing the expected average GFA per flat (flat size) by the expected persons per flat (ppf).

4.1.8   The definitions of various site areas used in these guidelines are illustrated in Figure 1.

4.2     Treatment of Open Space

4.2.1   Open space generally refers to an area which would merit the "O" zoning on town plans. In determining the development capacity of a site, the treatment of open space provision needs further elaboration since it may take various forms and can be more flexibly designed than other supporting G/IC facilities.

4.2.2   In new development areas, adequate provision of open space should normally be made on town plans at HKPSG standards, according to the project population. In such areas, therefore, the NSA should be used to calculate the gross floor area for a site, according to the provision of the B(P)R, subject to any control that may be stipulated in the land lease or the statutory OZP.

4.2.3   In those built-up areas where there is inadequate reservation of open space, residential development should as far as practicable not be allowed to aggravate this situation and consideration should be given to zoning additional open space, particularly with regard to District Open Space. However, if there are strong justifications for and significant planning benefits from a proposed housing development, the project may be permitted but the following should be considered:

                      (a)     Where it can be demonstrated that the layout can satisfactorily accommodate the Local Open Space (LOS) requirement relative to the assumed design population, the NSA can be used in full for plot ratio calculation purpose.

                      (b)     However, if the plot ratio generally applicable to the area would likely result in a population too high to permit such self-containment of LOS, consideration should be given to reducing the permissible GFA on the site to a level at which it can be achieved. 

5.1     The chart in Table 6 converts building density or plot ratio into population capacity on sites of different areas. It takes account of the effects of variations in occupancy rates (flat size and ppf) on the facilities required and therefore the NSA. It is intended to be used to obtain initial estimates of population capacity and land requirements for strategic and district planning purposes, when limited site-specific data is available. It incorporates fixed assumptions about standards for the provision of Local Open Space and School facilities (given in Table 7) and roadspace. It requires the input of assumed values for:

        (a)    development site area (the estimated developable part of the gross site area)

        (b)    plot ratio (according to the proposed density zoning)

        (c)    average domestic GFA per flat

        (d)    average persons per flat

5.2     If no specific values are available for items (c) and (d) above, the latest available assumptions relevant to the area and the likely date of occupation should be used. Otherwise, the initial assumptions given in Table 8 and Table 9 may be used as a rough guide. However, appropriate judgement should be made upon application of average flat sizes for planning purpose since those figures are highly volatile and would vary according to the factors like price, location and affordability, etc.

5.3      The key variable in the chart in Table 6 is NSA per person (NSApp). This is obtained from inputs (b), (c) and (d) above, by dividing average flat size by average persons per flat and dividing the result by plot ratio. The chart shows the population capacity of any DSA for a set of alternative NSApp values. If no portion of a site is required to be set aside for Local Open Space, i.e. excluded from the NSA (see para 4.2.1), the NSApp value should be reduced by 1.0.

5.4     The chart can be used for the three purposes listed in section 4.1.1, as follows:

                    (a)     To estimate the population capacity of a site area at a given plot ratio, calculate the NSApp from the appropriate input values and select the curve on the chart with the closest NSApp value. Where this NSApp curve intersects with the given DSA on the horizontal axis, read off the corresponding population on the vertical axis. Values for intermediate NSApp levels may be obtained by interpolation.

                    (b)     To estimate the site area required to accommodate a given population at a given plot ratio, select the curve for the appropriate NSApp value as in (a). Where this curve intersects with the given population on the vertical axis, read off the corresponding DSA on the horizontal axis, by interpolation if necessary.

                    (c)    To estimate the plot ratio required for a given population to be accommodated on a given site area, find the NSApp curve closest to the intersection of the DSA value on the horizontal axis and the population value on the vertical axis, by interpolation if necessary. Calculate the GFA per person (GFApp) value by dividing the appropriate flat size assumption by the ppf assumption. Divide the GFApp by the NSApp from the chart to give the required plot ratio. Examples of how the graphs are used are shown in Appendix 1, and an explanation of their form is given in Appendix 3.

5.5    The results derived from using the chart in these ways will show the combinations of population, site area and plot ratio necessary to achieve a comprehensive development which will satisfy HKPSG standards for the provision of open space and G/IC facilities, on the basis of average values for the key occupancy variables. Typical gross population densities for sites of different areas in Residential Zones R1, R2, R3, RR1 and RR2 are shown in Table 10. These population densities are for illustrative purposes only and do not represent targets.

Net to Gross Ratios

5.6      In considering the development capacity of a large site, it is useful to be able to make a broad assessment of the proportion of a site which will be available for residential development (NSA), and the proportion which will need to be set aside to accommodate roads, open space and G/IC facilities. The ratio of the NSA to the DSA varies with the NSApp and the gross area of the site. For Residential Density Zones R1, R2, R3, R4, RR1 and RR2, it can be read from the chart in Table 11. The specific G/IC facilities that are estimated to be required can be read from the population threshold levels set out in Table 7.

6.1       For site planning, it is likely that more site-specific data will be available on, for example:

                    (a)    the proportion of the gross site area not available for development due to slope, primary or secondary roads, and other uses not ancillary to the proposed development;

                    (b)    the proportion of the developable area which will be required to accommodate internal roads; and

                    (c)    the requirement for open space and G/IC facilities to serve the development, in the light of existing or proposed provision in the district as a whole.

 6.2     If such information varies significantly from the average values for these items given in Table 7, the latter will not be an adequate guide for site planning purposes. A computer program has been developed which can convert building density to population using any values for the key variables, including those which were held constant for the chart. This program, entitled the SUM2 Model, is described in Appendix 2 and intended for reference only.

6.3     The SUM2 Model will also provide a preliminary assessment of the portion of the GSA which will be available for residential development, i.e. the NSA. The ultimate value for the NSA from which the permissible domestic GFA is calculated is derived by the iterative process of drawing up and refining a layout.