Rear extension in South Cambridgeshire: Planning Permission Guide
Everything you need to know about building a rear extension in South Cambridgeshire, including permitted development rules, typical costs, and which professionals you'll need.
Check if your rear extension qualifiesRear extensions in South Cambridgeshire at a glance
approved
application fee
weeks typical
Based on 93 decided applications in South Cambridgeshire over 12 months (86 granted, 7 refused).
South Cambridgeshire has 85 conservation areas — extensive heritage coverage restricting external alterations across many streets. 9 Article 4 directions affect specific streets. Over 5,000 listed buildings recorded across the borough. South Cambridgeshire planning is run by the Greater Cambridge Shared Planning Service (jointly with Cambridge City).
Want your personalised odds?
Approval probability, 5 nearest comparables, refusal reasons — for your specific address.
Recent rear extension decisions in South Cambridgeshire
The 5 most recent decided applications. Addresses redacted to postcode area.
S73 to vary conditions 2 (approved drawings) and 3 (materials) of planning permission 25/04034/HFUL (First floor rear extension, addition…
Alterations to garage and link building with first floor side extension and single storey rear extensions, replacement of all existing wi…
Two storey rear extension and single storey infill extension.
Single storey rear extension.
First floor rear extension over existing garden room. Ground floor infill under existing side bedroom
These are borough-wide. See the 5 nearest to your address.
Get my report — £9Permitted Development Rules
Enlargement, improvement or other alteration of a dwellinghouse
GPDO 2015, Schedule 2, Part 1, Class A
Rear extensions fall under Part 1, Class A of the General Permitted Development Order (GPDO). This means you can often build one without a full planning application, provided your project stays within the dimension limits.
Key dimension limits
Single storey
Two storey
These are the maximum GPDO limits for a detached house with no constraints. Your actual limits depend on your property type, location, and any planning restrictions.
Enter your postcode to see the personalised limits for your rear extension.
Check my limitsTypical Costs in East of England
Construction costs for rear extensions in East of England vary depending on size, specification, and whether you're building single or double storey.
Cost per m²
construction rate
Typical total
Based on 12–18 m²
Cost per m²
construction rate
Typical total
Based on 20–35 m²
Typically includes
Typically excludes
Double storey extensions have a lower per-m² cost as foundations and roof are shared across two floors.
Get a personalised cost estimate based on your actual rear extension dimensions.
Get my estimateWhich Professionals Do You Need?
The professionals you'll need depend on the size and complexity of your extension, your property type, and whether you share walls with neighbours.
You'll need a party wall surveyor for this project.
A draughtsperson or architectural technician can prepare the plans needed for a single storey extension. A full architect may not be necessary.
Typical fee: £1,500–£3,500 (Plans + Building Regs)
Single storey extensions typically need structural calculations for any openings in existing walls and for foundations.
Typical fee: £500–£1,500
Your semi-detached house shares a boundary with neighbours. Extensions and loft work within 3 metres of a shared wall trigger the Party Wall Act.
Typical fee: £700–£1,500 (per neighbour)
This guidance is based on a typical semi-detached house with no special constraints. Listed buildings, conservation areas, and attached properties may require additional professional input.
Find out exactly which professionals you need for your rear extension.
Get personalised guidanceConservation Areas & Listed Buildings
If your property is in a conservation area, the maximum depth for a single storey rear extension is reduced to 3 metres for all property types. Two storey rear extensions are not permitted in conservation areas.
Properties in conservation areas often have reduced permitted development rights. Some project types (like side extensions) lose PD rights entirely. An Article 4 Direction can remove additional PD rights.
Listed buildings (Grade I, II*, or II) have no permitted development rights at all. Any external alteration requires Listed Building Consent in addition to any planning permission. An architect experienced in heritage work is essential.
Check if your property is in a conservation area or has other planning constraints.
Check my propertyPrior Approval (Larger Home Extension Scheme)
Single storey rear extensions between 4m and 8m deep (detached) or 3m and 6m deep (other houses) may be built under the "larger home extension" scheme. This requires a Prior Approval application with a neighbour consultation — not a full planning application. The fee is lower and the decision is faster.
Frequently Asked Questions
Just want a quick yes/no for your rear extension?
Run our free 2-minute check to see whether your project likely qualifies as permitted development in South Cambridgeshire. For personalised approval odds and nearby comparables, get the full report above.
Free 2-min check