Key Terms and Definitions

Affordable Housing    

There is no agreed definition of Affordable Housing. The most commonly referred to definition is in Annex 2 of the NPPF, which defines it as housing for sale or rent which provides a subsidised route to home ownership, or alternatively is for local essential workers. There are a number of key types as defined in Annex 2:

  1. Affordable housing for rent
  2. Starter homes
  3. Discounted market sales housing
  4. Other affordable routes to home ownership

Alternative Use Value (AUV)

Alternative Use Value considers other options for a property to identify the highest value and best use for the land. There’s usually more than one thing that can be done to release value in a site.

Government guidance allows viability assessors to consider the alternative use value of a building as a benchmark, provided this relates to a lawful use which complies with the adopted development plan. This alternative use can therefore be:

  • a legal permitted change of use or development(which does not require planning permission) 
  • an existing planning permission (for example a smaller scheme)
  • or a proposal which fully complies with all development plan policies


Building Cost Information Service – Recommended source of information on average build costs which can provide a rough rule of thumb for development costs. Generally this underestimates costs compared to an accurate QS cost plan, and is based on historic information, so not always representative of inflation.

Benchmark Land Value (BLV)

A Benchmark land value is established as part of the viability process. This is usually based on an existing use value for the land plus a premium for the landowner. The benchmark land value should also reflect the implications of abnormal costs, site-specific infrastructure costs, and professional site fees.

Enabling Development          

Enabling Development is defined by paragraph 202 of the NPPF as development that would not be in compliance with local and/or national planning policies, and not normally be given planning permission, except for the fact that it would secure the future conservation of a heritage asset. More information can be found on our Enabling Development page.


Existing Use Value      

Existing use value is not necessarily the market value of the land. Government guidance suggests this should be the value of the land in its existing use without any ‘hope value’ added, and notes that market transactions can result in a buyer under or overpaying for property.


The National Planning Policy Framework sets out the UK Government's policies for planning, along with information on how said policies are expected to be applied.

Optimum viable use

Optimum viable use is used in situations where there are a number of options available for a site, and it tends to come up regarding heritage assets and enabling development. Advice written by Historic England states that if there is one possible use, that is the Optimum Viable Use. If there are arange of options, the term applies to the use likely to cause the least harm to the significance of the historic asset.


As part of the benchmark land value, premiums refer to the amount above the existing use value which goes to the landowner – therefore providing a reasonable incentive for the landowner to bring it forward for development.


Supplementary Planning Guidance, or Supplementary Planning Documents provide further guidance about the implementation of specific planning policies, or on developments in specific areas and on certain sites.  



When we talk about thresholds regarding planning obligations,we mean the trigger point at which your development will be asked to provide either affordable housing, or cash in lieu. According to the NPPF, major developments should be providing affordable housing – this is defined in the NPPF appendix as anything over 10.

Many local plans set individual thresholds which can be below this point.

Urban area    

Urban areas are usually defined as built-up areas with highpopulation density, incorporating cities, towns, and suburbs.

High Section 106 costs are avoidable

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