Do Parameter Plans protect design intent?

Almost as much work is required for an outline planning application (OPA) as a ‘detailed’ or ‘full’ planning application. This is costly and time consuming for all parties -  including planning committees who have to wade through masses of information in order to make their decisions.

Image created by Adobe Firefly AI

OPAs set out binding parameter plans covering Land Use, Green Infrastructure, Access and Movement and Density and Heights. OPAs also set out the design intent in a Design and Access Statement which will include an illustrative layout with various drawings and models to show how the development could be designed within the parameter plans.

These binding plans do not tell us much about what we can expect to see once the detailed application comes forward, other than a two dimensional mapping of the site. The Density and Heights Parameter Plan/s should tell us a bit about the three dimensional parameters but herein lies the problem:  not many people truly understand density.

The purpose of a density parameter plan does vary from one application to another as shown on the two examples below:

‘The aim of the Parameter plans (or Maximum Development Plans) is to set principles for the minimum and maximum development opportunities across the site. They prescribe clear rules that will regulate any future detail design proposals, while allowing the required flexibility to accommodate for potential updates in policy, standards and changing local needs as each phase is being delivered.

Cornwall Council and Treveth Development LLP

‘The Density Parameter Plan was prepared in order to establish a density framework to guide the future scale and appearance of the proposed development. Density is measured as Dwellings per Hectare (dph) and the plan shows a range of densities for different areas of the site.’

Suffolk County Council

A quick Google search for “Density Parameter Plans” will immediately bring up a number of planning applications which illustrate how meaningless these plans are when the relationship between housing mix and density is not understood. Below are the first two examples that came up :

Example A - 1202 units.

‘The overall density of the site will be approximately 35dph with higher densities in the centre of around 40dph, whilst lower densities at around 30dph will be characterised by larger detached properties with deeper frontages and gardens’

30dph can not be achieved with larger detached properties and an overall density of 35dph will require a far higher density than 40dph at the top end of the range.

Example B - 400 units

This application includes a Design and Access Statement with a Density Parameter Plan, Storey Heights Parameter Plan and a Character Area Plan. This application states:

‘There will be 18 private for sale bungalows and 37 affordable bungalows’.

18 two bed bungalows will require at least 1 hectare, 55 will require 3 hectares . This site is 11 hectares and the proposal is to accommodate 400 units at an average density of 35dph.

18 bungalows on a one hectare tile (from the Bluepencil Manual of Housing Density)

55 bungalows  on 3 hectares will mean that the other 382 units will need to be accommodated on 8 hectares at an average density of 48dph. To achieve the unit numbers at this density means a minimum of  40% three storey apartments. Completely different to the design intent set out in the Design and Access Statement.

The alarming future for the application in Example B is that the end result will not be what was envisaged and consulted on at the Outline Application Stage.

In Example A and B the designers did not understand the relationship between density and mix so it is no wonder that planning committees have difficulty!

To make matters worse, not only are the three dimensional parameter plans not understood by either the designers or the decision makers, the parameters are also usually widened ‘to give flexibility’. In the case of density this widening is in the form of ‘ranges’ or ‘density bands’. A soon as you widen the ranges or bands you unravel the design intent. The only way to ensure the parameter plans protect the design intent is to make them tighter and this requires a deeper understanding.

The  illustrative layout could be very helpful in protecting the design intent if it were less illustrative and more definitive. The Parameter Plans themselves will not.

For more information on density see: The Manual of Housing Density available as a free download from the resources page of this website.