Plan Then Build

Two-storey extension cost in South East

South East build costs run at 115% of the UK national average, across councils including Brighton and Hove, Oxford, Reading. A 20m² example at mid-range spec: £85,512–£115,692. Adjust the size and spec below for your project.

Permitted Development & Cost Checker

England only. Takes about a minute.

Two-storey extension cost by size and spec in South East

SizeBasicMid-rangePremium
15£44,537–£60,256£64,134–£86,769£91,846–£124,262
20£59,383–£80,342£85,512–£115,692£122,461–£165,683
30£89,075–£120,513£128,268–£173,538£183,692–£248,524

Does a two-storey extension need planning permission?

Council planning fees in South East

Each council sets its own fees and decision times. See your council’s page for the exact figures.

Two-storey extension cost in other regions

Cost bands refreshed quarterly from published 2026 UK cost guides.