Spatial and Density Analysis
In this chapter, we set out the findings of our spatial and density analysis.
This analysis aims at addressing the following questions:
1—How does the density of London’s existing large estates compare to surrounding ward densities and borough densities?
2—How dense are London’s existing large estates, and how does this density relate to the London Plan density guidelines?
3—How many additional units would be gained by bringing estate density up to ‘urban’ density levels?
4—How many additional units would be gained by bringing estate density up to ‘central’ density levels? We identified a sample of four London boroughs: Barking and Dagenham, Hounslow, Lewisham, and Waltham Forest.
When combined, these account for approximately 13 per cent of London’s social housing stock (See Appendix A for the full list of sample borough criteria). We analysed the density of large estates – those comprising at least 200 dwellings. 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 space for newcomers.
Roughly 17,500 dwelling units have been identified in these boroughs’ 36 large estates. Large estates in Barking and Dagenham, Lewisham, and Hounslow all had similar densities, with an average of 86 dwellings per hectare (dpha). However, large estates in Waltham Forest had an average density of 167 dwellings per hectare.
In all four boroughs, estates were generally denser than their average borough residential densities. With the exception of those in Lewisham, large estates were roughly as dense or denser than the wards they are part of. This is not to say that these estates constitute the best possible use of land, but to highlight that in three out of the four boroughs, the density of large estates is not significantly lower than that of the surrounding area.
Table 1: Summary of current capacities and densities
Figure 1: Density comparisons of the four boroughs and their large estates
Comparing estates to London Density guidelines
The Sustainable Residential Quality (SRQ) density matrix forms part of the London Plan’s policy on the density of new housing, setting density ranges on the basis of public transport accessibility and neighbourhood setting (defned as ‘suburban’, ‘urban’ and ‘central’). The SRQ matrix has been used to test the scope for estate densifcation beyond the levels of estates’ surrounding wards.
The assessment reflects transport accessibility, but has made some assumptions in terms of setting. Planning guidance suggests that larger sites like these can, in any case, ‘define their own setting’.16 We used an average dwelling size of 3.1–3.7 habitable rooms per unit, allowing for a good proportion of family homes.
We estimated the uplift (in number of homes) that could be achieved on large estates in London if they were raised to the upper limits of both ‘urban’ and ‘central’ densities, at an average PTAL of 2–3. These densities are 145 and 210 dwellings per hectare respectively. The former is similar to the current average new build density in London of 153 dwellings per hectare. Our four-borough sample gives us an estate density average of 90 dwellings per hectare, showing there is scope for densifcation by both measures.
Scenario one: ‘Urban’ Density Settings
When comparing densities using the SRQ ‘urban’ setting, our modelling shows that there is some scope for increasing density. Densifying all large estates in the four sampled boroughs to the upper limit of the SRQ ‘urban’ level could theoretically provide around 10,000 new homes. Densification of Hounslow estates could yield the largest number of new homes. Upwards of 3,500 homes could be added to these estates, which is an 81 per cent uplift on their current large estate capacity. Barking and Dagenham could gain almost as many homes. Lewisham has the potential to achieve a 52 per cent uplift, providing 3,300 new homes for the borough. Only 22 per cent of estates in Waltham Forest could be densified in this scenario, providing fewer than 500 new homes.
Table 2: Summary of densities and potential unit gain if large estates are raised to maximum ‘urban’ density
Scenario two: ‘Central’ Density Settings
Our modelling suggests that densifying estates up to the SRQ ‘central’ setting could produce substantial housing gains of over 20,000 new homes in the four boroughs, with Waltham Forest again providing the least scope. The other three boroughs have the potential to double their current estate housing capacities – in fact, estate densification could increase Barking and Dagenham’s total housing stock by 10 per cent.17 If we assume the current borough ratio of total homes to social rented homes is replicated with the additional homes on large estates, 13 per cent of the current local authority waiting list in Barking and Dagenham could be housed.18 Figure 2 shows that at ‘central’ level, densification on estates in all boroughs except Waltham Forest could meet at least half of their boroughs’ ten-year minimum housebuilding target, and could fulfil Hounslow’s ten-year need almost entirely.
Table 3: Summary of densities and potential unit gain if large estates are raised to maximum ‘central’ density
Figure 2: GLA housebuilding target by borough compared to potential uplift (in number of dwellings) on large estates if raised to maximum ‘urban’ and ‘central’ densities
Reaching a London figure
Using our four-borough sample, we have also produced an estimate for the additional homes that could be created through an increase in densifcation of large estates in London to both ‘urban’ and ‘central’ densities.
Overall, our model has picked up between 20 and 40 per cent of socially rented housing in each borough. Using the values from Table 3, we calculated the total uplift (in number of homes) at both ‘urban’ and ‘central’ densities as a percentage of the total number of dwellings socially rented from the local authority in the four boroughs. We then used this percentage to calculate the uplift on all London boroughs, using their social housing stock as a proxy for the number of housing estates they accommodate. We then calculated the London total uplift at both ‘urban’ and ‘central’ densities, and used those values as our upper and lower bounds respectively. A detailed methodology can be found in Appendix A.
We estimate that estate densification has the potential to add between 80,000 and 160,000 homes to London’s large estates.
The speed at which a redevelopment project can proceed will depend on a range of factors, the most significant are: the time it takes an authority to decide on redevelopment, to rehouse the residents, and for the developer to build out at a rate the market can absorb. The base case we modelled takes 11 years from start to finish. If all the large estates that are capable of densification were to be redeveloped then it would take at least 10 years for all of these projects to start. The last output of additional housing could be 20 years away. It is for this reason that we have divided the total potential of additional housing by 20 to get an approximate annual contribution to London’s growth needs.
We estimate that estate densification has the potential to add between 4,000 and 8,000 homes to London’s large estates each year – up to 20 per cent of London’s annual additional housing target.
It is also important to note that, for the majority of sites, the uplift potential will likely be closer to the lower bound, as ‘central’ densities will be reserved for town centres. Our London range does not include medium to small estates, although we do envisage that there will be more scope for densification, varying borough by borough, if they are included. We hope to cover this in more depth in a future Centre for London report.
Figure 3: The potential annual uplift range from densification compared to the GLA’s yearly housebuilding target
Urban opportunity London’s housing shortage needs to be tackled strategically, incorporating densification, good design, and social considerations. As has been shown, London’s large estates have the potential to make significant contributions to this solution. Introducing ‘central’ (or even ‘urban’) level densities to large estates in Outer London boroughs would likely involve major changes to neighbourhood characteristics, and would need to be carefully considered in both the design and community consultation. At the same time, it should be noted that less than half of all new developments in London are within their suggested density ranges, with 51 per cent of residential approvals granted to developments above their given density range.
In order for the SRQ matrix to become a more effective and more widely used development tool, it needs to take account of more sophisticated approaches to reflecting London’s changing urban form, and the linking of density and transport. It is important that the matrix acknowledges the growing importance of densification, alongside new build, as a means of creating additional housing units in London. Since many estates are not at a particularly low density (especially in comparison to surrounding areas), our analysis suggests that densification should not stop at the edge of housing estates.
The reasons are twofold. First, a more integrated approach would forestall perceptions that estates are being ‘singled out’ for redevelopment. An approach that combines densification both of estates and other housing or land use can help open up the debate in terms of how we view different parts of London and the role that these areas should play in boosting the capital’s housing supply. Second, estate densification also needs to be carried out in a way that integrates the densified site with the surrounding urban fabric, adopting a mixture of block types and an increase in density nearer to urban centres and transport hubs.
As noted in Appendix A, our uplift estimation for London’s estates should be used with caution. Alongside the methodological caveats to our approach, the numbers we arrive at are illustrative, and do not account for the fnancial viability of potential densifcation schemes.
The next chapter of this report looks at the financial feasibility of estate redevelopment.