PropeteerProperty intelligence

Planning guide

Buying a house with an extension

Do not assume an existing extension is authorised because it is visible or old. Compare the physical building with planning records, approved drawings, building-control evidence and the seller’s documents, then let the conveyancer decide what formal enquiries are required.

Written and reviewed by Propeteer Research TeamPublished Reviewed

At a glance

Key facts

Planning evidence
Permission, prior approval or lawful-development record
Separate question
Building regulations approval
Physical check
Does the built form match the approved drawings?

A reliable process

How to approach the question.

  1. 01Identify the extension’s approximate age, footprint, height and use.
  2. 02Match it to planning applications, prior approvals or lawful-development certificates.
  3. 03Compare the approved plans with the current layout and exterior.
  4. 04Raise missing or inconsistent records with the surveyor and conveyancer before exchange.

Worked example

A rear extension with no obvious application

A modest single-storey extension may have used permitted-development rights, but that cannot be assumed from its size alone. Article 4 directions, listed status, previous alterations and the rules in force at the time can change the answer.

What this does not prove

  • Open records do not establish legal compliance.
  • Planning permission and building regulations are different regimes.
  • Time limits, enforcement and indemnity decisions require legal advice.

Method used

  • Confirm the subject property and distinguish applications at the address from wider local context.
  • Classify proposal type and outcome consistently, keeping pending, withdrawn and approved-with-conditions cases separate.
  • Give more weight to recent, similar and well-documented decisions; retain contradictory evidence rather than hiding it.

Primary sources and official guidance

Planning PortalPlanning PortalLocal planning authority registersUK local planning authoritiesHow to buy a homeMinistry of Housing, Communities and Local Government

Source scope, licensing, refresh expectations and known limitations are listed in the public data-source register.

Related guides

How to check the planning history of a property

Find and interpret planning applications, decisions, drawings and conditions for a UK property without confusing nearby records with the subject address.

Article 4 directions explained

Understand how an Article 4 direction can remove specified permitted-development rights and what to verify before relying on general rules.

Apply this guide

Start with the exact UK address.

Research a property