The recent publication of larger than expected population growth figures will require many authorities to reassess their housing need and supply calculations and add further pressure on them to grant permission for new housing developments.

The latest ONS figures show that the population growth in the UK and particularly in London and the south east are higher than expected. This has the potential to worsen the existing housing crisis.

The new population growth figures will also fuel the arguments over what is necessary to meet the 5 year supply of deliverable housing sites required by the National Planning Policy Framework (NPPF). Without that 5 year supply, local plan policies on housing will be deemed out of date with a presumption in favour of granting planning permission for housing taking centre stage.

Recent appeal decisions are, at best, unhelpful and at worst contradictory. So how should the 5 year supply be measured?

ST ALBANS: ASSESS UNCONSTRAINED NEED

We should start with a visit to St Albans. In the case of Hunston v Secretary of State in 2013 the court confirmed that in assessing housing need those local planning authorities without an up to date local plan (one that has been assessed and adopted after the NPPF came into force in March 2012) must use an unconstrained basis for the calculation, that is, ignoring any restrictions such as green belt that may otherwise prevent development in their area. This is mirrored by paragraph 47 of the NPPF.

That unconstrained basis for calculating need should take into account population growth. As that is greater than previously thought there are arguments for revisiting any assessment of housing need that has not taken it into account.

SEDGEFIELD: DEALING WITH UNMET DEMAND

We then visit Sedgefield for guidance on how previous unmet demand should be taken into account. In 2009, the government used examples of appeal decisions from sites in Liverpool and Sedgefield to provide guidance on how to deal with previous under-delivery of housing. The “Liverpool” method spread the shortfall throughout the whole of the local plan period, whereas the “Sedgefield” method spread it over the first 5 years only. If the Sedgefield method is used then that should be added to the unrestricted housing need assessment. The Sedgefield method is now the preferred method and has been enshrined in the National Planning Policy Guidance.

In practice this means that assessments of housing need and the 5 year supply of deliverable sites pre-dating the latest figures might be out of date and at least should be subject to robust questioning. Whether the Planning Inspectorate in deciding appeals take this on board without the need for further guidance from the courts is an open question, recent appeal decisions indicate that there is still some way to go.