SPPS Strategic Planning Policy Statement Edition 2 (December 2025)ยทPage 69
Windfall Housing Allowance
Councils must make full allowance for windfall housing (unexpected development) when deciding how many sites to allocate for development in their plans, to avoid excessive allocation of land. Windfall allowances should be calculated using robust methodologies based on past trends and regularly monitored.
In line with the objectives of the RDS it is necessary to make full allowance for this when deciding the number of sites to identify for development in the plan to prevent excessive allocation of housing land. The scale of the windfall housing allowance will vary from area to area and may depend on the approach taken to the urban capacity study. Allowance can be made on the basis of examining past trends in windfalls coming forward for development and estimating likely future windfall potential. It is recognised that there is a range of methodologies for calculating windfall. The methodology used should be robust and care should be taken to avoid under-estimation of windfalls. Windfall should be regularly monitored because of its dynamic and changing nature, with monitoring data factored into the plans housing allocation when the LDP is reviewed.
Source โ /Users/richardhill/Documents/planning-arch-project/data/documents/regional/SPPS - Strategic Planning Policy Statement Edition 2 (December 2025).pdf