Job numbers in outline applications

12th May 2014

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Amy Dickinson

Environmental impact assessment (EIA) practitioners from David Lock Associates examine how potential job numbers are assessed in outline planning applications

Large-scale employment or mixed employment and residential development proposals are frequently promoted through the planning system through the use of outline planning applications, with detailed designs (known as reserved matters) fixed subsequently at a later date.

The outline planning process is well suited to such proposals in allowing the principle of development to be tested without the need to fix all aspects of design, and offering flexibility in the precise mix and disposition of land uses. EIA is often required depending on the scale of such development, its setting and the characteristics of the potential impacts.

The flexibility of the outline application approach has to be reconciled to the rigours of the EIA process which, in the case of infrastructure projects, will often require an assessment of the likely significant effects in terms of population, commonly assessed in terms of socioeconomic effects.

One particular aspect of EIA practice where this reconciliation is required is where employment development is promoted in an outline planning application. Employment uses are known as “B class” uses which fall within the following planning use classes:

  • B1 business (a) offices
  • B1 business (b) for research and development of products or processes
  • B1 business (c) light industry
  • B2 general industry
  • B8 storage or distribution

Many outline planning applications that include employment development are for large developments that will be developed over many years. Outline applications therefore seek to maintain flexibility in the range of employment uses that might come forward to provide the maximum opportunity for the needs of the market to be met, and to provide an outline planning permission with suitable flexibility to meet these needs over the long term.

A common approach is to identify in the description of the development of the outline planning application a maximum area in hectares or floorspace in square metres for B-class employment uses in use classes B1/B2/B8 which could theoretically accommodate any single B-class use or mix of B-class uses up to this maximum without prescribing a precise split.

Approaches to assessment

The assessment of possible socioeconomic impacts will seek to identify the likely effects on population arising from the development and the associated social and economic effects, including the level of job creation. The differing B-class uses have very different characteristics in terms of the numbers of jobs created as demonstrated below.

Table 1: Employment densities:

In assessing the level of job creation, assumptions have to be made regarding the likely floorspace of each B-class use over and above the flexible parameters established in the outline planning application.

Use class

Use type

Area per FTE (m²)

Floor area basis

Comment on potential variation






Range of 18-60m²

B1(c) Light industry (business park 47 NIA

Warehouse and distribution





Range of 25-115m² The higher the capital intensity of the business, the lower the employment density

B8 Large-scale and high-bay warehousing 80 GEA Wide variations exist arising from scale and storage duration



General office



Includes HQ, admin and client-facing office types


Call centres



IT/ data centres



A blended rate of the above B1(a) uses where they are found in out of town business park locations


Business park


NIA A blended rate of the above B1(a) uses where they are found in out of town business park locations

Serviced Office


NIA Densities within separately let units are c.7 m² per workstation but 30% of a facility's total NIA for shared services reduces the overall density

Source: Employment densities guide, 2nd edition, 2010, Homes and Communities Agency

There are three possible approaches towards identifying the likely job numbers and associated likely significant effects:

  • Worst case: One approach is to assume the maximum possible job creation and therefore maximum possible effect (or the “worst case”). This would generally involve assuming that the majority, if not all, of the floorspace created would be in office use which has the highest employment density.
  • Likely case: A second approach is to promote a balanced mix of likely employment uses from across the spectrum of likely uses. The mix will depend on the specifics of the scheme promoted.
  • Identifying a range: Another approach is to acknowledge the uncertainty that exists about the final mix of B-class uses and to test a range of likely mixes (such as an office-led or industry-led scenario). The likely job numbers would therefore be identified within a range.

The approach adopted will also need to be consistent with the other assessments required to be undertaken in support of the outline application or EIA. Differing B-class uses have: different trip generation characteristics in transport terms; different visual effects in terms of the size and scale of built form; and different characteristics in terms of the production of waste, noise or pollution.

Experience suggests that many of these characteristics can be accommodated within suitable parameters and mitigants (such as building height and strategic landscaping for visual effects). However, the issue of trip generation is often the most volatile characteristic of employment uses in terms of the number of trips generated; the timing of the trips in peak hours; the mix of HGV trips and car trips; and the associated impacts of the trips on other assessments, notably noise and air quality.

On this basis, an outline application and EIA that assesses a likely case employment mix offers significant advantages in avoiding the exaggeration of trips that a worst case assessment would offer, while testing a reasonable maximum.

The final mix of B-class uses must be kept under review at the reserved matters stage to ensure that parameters tested at the outline stage are adhered to or, if the parameters are varied in some way, that likely significant effects are screened to ascertain whether further EIA is required.

Planning conditions should also be used at the outline stage to ensure that the parameters tested by EIA are properly reflected in subsequent reserved matter submissions.


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