Mill Hill Preservation Society
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Mill Hill Preservation Society

Density in Planning

1.1 When we discussing schemes in committee at the MHPS the matter of ‘density’ often comes up. For instance ‘over-development’ implies too high a density. Density used to be a measure of the number of habitable rooms per acre. The modern measure is more often quoted as the number of dwellings per hectare. I collected some details on density from various sources to highlight the changing situation, and then give some examples of local sites to explain more fully what they mean.

Government Policy:
2.1 The RIBA have highlighted the current density advice from the Office of the Deputy Prime Ministers (ODPM) as follows...

“All those that have an eye on the government’s housing Growth Areas should note that the Density Direction introduced in the South of England now applies. Announced this week (26.1.2005) as yet another plank of the five-year plan, the extended direction requires planning authorities to refer any large housing development with a density less than 30 dwellings per hectare to the Secretary of State.”

2.2 Since the direction was introduced, average densities of new housing developments in London have increased from 55 to 71 dwellings per hectare (p/ha). In the South East average densities of new housing development have increased from 26 to 33 dwellings p/ha. While guidance for housing density is set out Nationally in PPG3, ministerial intervention – or the threat of it – puts pressure on planners facing ‘relaxed’ development proposals.

Planning Policy Guidance 3: (PPG3)
3.1 (Extract from PPG3…) ‘Local planning authorities should avoid the inefficient use of land. New housing development in England is currently built at an average of 25 dwellings p/ha – but more than half of all new housing is built at less than 20 dwellings p/ha. That represents a level of land take that is historically very high and which can no longer be sustained. Policies which place unduly restrictive ceilings on the amount of housing that can be accommodated on a site - irrespective of its location and the type of housing envisaged or the types of households likely to occupy the housing - should be avoided’.

3.2 ‘Planning Authorities should therefore:

  • Avoid developments which make ineffective use of land’ - especially those of less than 30 dwellings p/ha.
  • Encourage housing development which makes more efficient use of land i.e. between 30 – 50 dwellings p/ha.
  • Seek greater intensity of development at places with good public accessibility such as city, town, district and local centres or around major nodes along good quality public transport routes.

How this might apply to NW7:
4.1 In NW7 we do not seem to be an area where densities as high as 70+ will apply. However, it does seem that densities in the region of 30 – 50 may be relevant in certain locations. On the other hand developments below 30 dwellings p/ha will be discouraged and may be called in. Whilst we may not agree with these policies they will probably be driving any planning applications that we consider ‘over-development’ and to a certain extent Barnet are encouraging the process.

Barnet Policy:
5.1 Barnet has a policy to increase densities wherever possible. The Barnet Housing Strategy states “To increase density through high quality design”.

Some Sums:
6.1 Taking the ‘benchmark’ of 30 dwellings p/ha what does this mean? Well, a hectare is 10,000 sq. m. and dividing one into the other gives 333 sq. m. per dwelling ‘gross’ - gross as the overall density would allow for roads, footpaths and green space etc. This would probably net down to an individual house plot size of 12m x 22m or 264 sq. m. For comparison the small house recently built in Burton Hole Lane has a plot size of about 14m x 20m or 280 sq. m. - capable of meeting a 30 dwellings p/ha criteria. The house won planning permission after an appeal, where the density factor was key.

Some Examples:
7.1 Ilooked at my own house and this has a plot size of 15m wide and 54m long to the edges of the roads – an area of 810 sq. m. This is 0.081 hectares. A development of such plot sizes would give an overall density of about 12/15 dwellings p/ha.

7.2 This density does not meet half of the PPG3 guideline of 30 dwellings p/ha minimum. To achieve the 30 dwelling p/ha standard I would have to have my house on a plot which comprised the house and back garden only – with no front garden at all – a plot of some 330 sq. m. and my front garden is bigger than my back!

7.3 Next I looked at John Turtles house. His plot is approximately 38m x 11m an area of about 0.042 hectares. Therefore a development of such plot sizes would give an overall density of about 23/4 dwellings p/ha – close to the National Average.

7.4 Finally I looked at a critical part of the Conservation area – The Chalet Estate (The Drapers’ Cottage Homes) on Hammers Lane. I estimate the area of the estate to be about 3.2 hectares according to my conservation area map. I estimate there are about 80 dwellings on the estate - this gives a density of 25 dwellings p/ha.

Interestingly this on is the National average – and below PPG3 guidelines – surprising, given the open feel to the estate. The fact that the dwellings are quite small, mostly single storey, and on an open site with great views out over fields, all contribute to the feeling of open space. If the plots were all 2/3-storey with 4/5 bedroom houses, with bigger footprints, it would not look or feel the same. This is why the ‘density’ planning guideline based on dwellings per hectare (p/ha) is such a clumsy tool.

Green Belt:
8.1 Whilst doing this exercise I thought I had the opportunity to add some comments on the Greenbelt. PPG2 lays down policy for the Greenbelt: Government policy is that each English region should be maintaining or increasing the area designated as green belt in local plans. Barnet policy aims to prevent urban sprawl by keeping land permanently open. “Barnet Council has consistently safeguarded the green belt by resisting inappropriate development and will continue to do so”. (They state …)

9.1 We all have met these issues before is some guise or other. It is clear that over time the escalating population is will add pressure on land use. There will be an effort to hang on to the Green Belt. This means that building density on the ‘presently built-on’ land has to increase over time – and may be this increase will be significant.

9.2 Conservation areas are special places. Whilst MHPS may lose some battles over density in general NW7 area, we need to be able to protect the Conservation Area. It is likely that we may have to fight very hard on density issues on new build sites – whether in the Conservation Area or not. We should be able to protect the Green Belt as long as the National Strategy and Barnet Council policy continue to be geared this way – otherwise this aim will be very difficult without legislative support.

9.3 I hope that my effort to bring these strands together in a concise format will enable those not involved with day to day planning issues in MHPS to be more aware of current policies. Hopefully we can all contribute to a more informed debate about these matters when needed on specific projects. The situation is fluid. If anybody on the committee can add to our knowledge please let me know and I shall update.

John Living 2006