Our evidence indicates that, in general terms, affordable housing should be viable to deliver at varying levels across the borough.

From time to time a developer or applicant may consider that the viability of a particular scheme is challenging for certain reasons. Where an applicant wishes us to consider a level of affordable housing provision below the policy requirement, we will require an 'open book' viability assessment. The viability assessment will be an objective test of the ability of a development project to meet its costs (including the cost of planning obligations), while ensuring an appropriate and competitive return for the land owner and the developer.

In the case of affordable housing, the viability assessment should robustly demonstrate at what level a proposed scheme would or would not be viable. Applicants' viability assessments should be detailed, show clear workings and be based on the most reasonable set of figures available including where appropriate, reference to RICS Building Cost Information Service data.

We will appoint an independent valuer to review viability appraisals submitted as part of a planning application. All initial appraisals and any subsequent reappraisals will be undertaken at the applicant's expense. The appointment of a valuer to undertake all appraisals and reappraisals will be made through the Hertfordshire-wide Viability Framework Agreement, which has been set up by local authorities across the County following a competitive tender in 2015.