Maximum extension sizes without planning permission — applied to Southampton City Council in the South East. With moderate Gateway 2 fire-safety scrutiny and an average build cost of £2150/sqm, the deal arithmetic for permitted Development Extensions here is distinct from neighbouring boroughs.
Southampton City Council does not currently operate Article 4 on residential PD, so permitted Development Extensions can proceed via the standard prior-approval route in most cases.
Run any South East listing through Scapely to get a property-specific build cost, council objection-risk score and the AI Objection Risk Analyzer overlay applied to Southampton City Council's policy environment.
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