Plan Then Build

Garden room / outbuilding cost in South West

South West build costs run at 105% of the UK national average, across councils including Bristol, Bath and North East Somerset, Exeter. A 20m² example at mid-range spec: £78,076–£105,632. Adjust the size and spec below for your project.

Permitted Development & Cost Checker

England only. Takes about a minute.

Garden room / outbuilding cost by size and spec in South West

SizeBasicMid-rangePremium
15£40,665–£55,017£58,557–£79,224£83,859–£113,457
20£54,219–£73,356£78,076–£105,632£111,812–£151,276
30£81,329–£110,033£117,114–£158,448£167,719–£226,913

Does a garden room / outbuilding need planning permission?

Council planning fees in South West

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

Garden room / outbuilding cost in other regions

Cost bands refreshed quarterly from published 2026 UK cost guides.