Appendix A

Another Storey: The Real Potential for Estate Densification

Appendix A

Spacial and Density Analysis – Methodology

We looked at large estates in four London boroughs to assess their potential for densifcation. Calculating the density of these large estates allowed us to compare the density of estates with that of their surrounding wards, and with the levels recommended in planning policy.

It should be borne in mind that these assessments were desk-based, and detailed design and planning work would be needed to translate indicative potential into reality – especially in order to achieve improvements in conditions for current residents as well as provision of additional homes for newcomers.

Selecting boroughs

We selected Barking and Dagenham, Hounslow, Lewisham, and Waltham Forest as our sample boroughs. This selection was based on the following criteria:

1—Including four London boroughs that contain approximately 13 per cent (four out of the 32 London boroughs) of London’s social housing stock when combined.

2—Including a mix of Inner, middle, and Outer London boroughs, as their social housing stocks have different confgurations and, we anticipate, different densities.

3—Excluding boroughs that have had large stock transfers to housing associations (on the assumption that these are already being more proactively managed).

4—Excluding those boroughs that have already been most active in estate redevelopment.


Finding high concentrations of social housing We extracted data using the 2011 Census from Neighbourhood Statistics and the Lower Layer Super Output Area (LSOA) Atlas.24 For all LSOAs in each borough, we recorded the total dwellings, the percentage of socially rented dwellings (from local authorities), and residential land use areas (domestic buildings plus domestic gardens). As a proxy for estates, LSOAs with over 32 per cent local authority-rented homes and at least 200 dwellings were examined more closely. The dwellings per hectare of their wards were also calculated for those particular LSOAs.

Locating estates

Google Maps and mapping software were used to manually search for estates within all identified LSOA’s with over 32 per cent socially rented, council owned homes. Only estates with over 200 homes were recorded. We identified sites that looked like estates (e.g. large blocks, green spaces and concrete playgrounds, as well as car parks and garages). For reliability, Google Street View was a second point of reference; many council estates had large signs at their edges, displaying council logos and site maps, which were used to confirm their identity. For Lewisham there was also a list of estates (provided by the borough in response to a 2010 Freedom of Information request). In order to verify findings, we checked this list after manually identifying the estates. No such data was publicly available for Barking and Dagenham, Hounslow, or Waltham Forest.

Using mapping software, we measured the land use area of each estate (in hectares). We took measurements from the pavements around estates, and we included roads that fell within the estate completely. Nonresidential buildings that were within estates were also included. The number of dwellings on each estate was verified on WhatAddress.  The density of each individual large estate (in dwellings per hectare) was then calculated. Finding the capacity for densification First, estate densities were based on the density of the ward they are situated in. If estates fell across ward boundaries, the density was based on the ward in which the majority of the estate is situated. Second, the density matrix was used as a benchmark on which to calculate the capacity for densification.

The density matrix

The Sustainable Residential Quality (SRQ) density matrix is a guideline set out in the London Plan. Taking into account other policy variations, the matrix includes wide density ranges. The density matrix is sensitive to variations in built form, massing, and PTAL. Its output values are in habitable rooms per unit, and dwellings per hectare. It is primarily intended for new developments. Two key variables affect the matrix: Public Transport Accessibility Levels (PTALs) and their neighbourhood typology. PTAL is a measurement of an area’s connectivity, for example the distance to a bus stop or train station. It is measured from six to zero, with six being the highest, and zero being the lowest. An area’s setting is classifed as either ‘central’, ‘urban’, or ‘suburban’. ‘Central’ neighbourhoods are dense, mixed-use areas with tall buildings, and are normally located near the city centre. ‘Urban’ areas are located near district centres, with buildings up to four storeys. They include buildings such as terraced houses, and low-rise apartment blocks. Dwellings in ‘suburban’ areas are usually limited to three storeys, and contain housing types such as detached and semi-detached. In order to calculate density in the London Plan, net residential site area is used – this includes non-residential land uses on sites, such as car parks, internal roads, and open spaces, but it does not include adjoining roads and paths. We estimated that there were 3.1–3.7 habitable rooms per dwelling, allowing for a good proportion of family homes to be included.


Two scenarios were set out: one in which all estate densities were to be raised to the upper limit of the ‘urban’ level, and the second in which all estate densities were to be raised to the upper limit of the ‘central’ level. For both scenarios (‘urban’ and ‘central’), the land-use area of each large estate was multiplied by the upper bound of the density matrix range at the midlevel PTAL (2–3). The potential increase in number of dwellings on each estate was noted.

Finding London’s capacity

We calculated the total number of homes that could be added to large estates in the four selected boroughs at ‘urban’ and ‘central’ settings. Our method for finding London’s total potential uplift was as follows:

1—We calculated the total uplift (in number of dwellings) in our sample.

2—We calculated the total uplift as a percentage of the total ‘number of dwellings socially rented from local authority’ in the four boroughs.

3—We multiplied this percentage by the ‘number of dwellings socially rented from local authority’ for each of the 33 Greater London boroughs, and calculated the total. 4—Our value for ‘urban’ was the lower limit for our range, and our value for ‘central’ was the upper limit.

5—We estimate that densification of this scale in London could take up to 20 years to complete (see Chapter 3), and therefore estimated the annual uplift range (in number of homes) that could be achieved by dividing our upper and lower limits by 20.

Methodological limitations

1—Finding high concentrations of social housing: Under our methodology, potential large estates in LSOAs with less than 32 per cent social dwellings rented from the local authority have been omitted from this study.

2—Locating estates: i) Estates were mapped by eye, so it is possible that smaller estates have been omitted. ii) Using our methodology, it was not possible to decipher which estates were actually council-owned, and how many socially rented dwellings were within those estates. iii) The areas calculated are not precise, therefore all values are rounded to at least iv) The gross area of each estate was measured, not just the net built area, or net residential area. Therefore the gross calculated densities are likely to be lower than those for individual blocks or land parcels. v) We did not differentiate between current estates that have been or are being densifed right now, and estates that have not been densifed.

3—Finding the capacity for densifcation: i) Some estates cannot be accurately compared to a single LSOA, ward or even borough, as they run over the boundaries. ii) We assumed that all densifed estates contained 7 habitable rooms per hectare.  iii) We assumed that bringing all estate to maximum ‘central’ or even maximum ‘urban’ densities will be appropriate – in terms of neighbourhood character, access to resources and services etc. iv) We have only focused on the homes that could be added through estate densifcation, and have not included other estate services such as shops or community centres in our density calculations.

4—Finding London’s capacity: i) We have decided to weight boroughs according to their social housing stock as a proxy for the number of housing estates. This does not take into account the differing configuration of social housing in different boroughs, or the extent to which redevelopment has already taken place. ii) Right to Buy has not been factored into the ‘number of dwellings socially rented from local authority’, because our sample showed that the proportion of Right to Buy to socially rented dwellings is roughly the same for London boroughs. Our sample demonstrated a range between 50 to just over 60 per cent of the dwellings remaining in council ownership.


1—Our London total assumes that there is unlimited funding for the schemes, and that all schemes are financially viable.

2—Within our 20-year timeline estimate, there are likely to be three or four years of no homes being built, as well as house building peaks later on.

3—In some boroughs there will be densification capacity in smaller estates, but we have not taken those into account for the purpose of this report.

4—Our estimates do not take into account the financial viability of estate densification projects, nor do they take into account the political feasibility of introducing higher densities.