How do I know if previous extensions had planning permission?

The starting point for checking whether an existing extension had planning permission is the local authority's planning register, which most councils now make available to search online by address, and which also holds the paper files for older applications. Searching by the property's Eircode, address or the owner's name at the time of the works should reveal any planning application relating to the extension, along with the decision and any conditions attached.

If no application appears on the register, this does not automatically mean the works were unauthorised — many extensions are legitimately built without a specific grant of planning permission because they relied on the exempted development provisions in Schedule 2 to the Planning and Development Regulations 2001. In that case, there may still be no formal 'grant' to find, though a well-documented sale should ideally include evidence, such as an architect's opinion on compliance or a section 5 declaration, confirming the exemption applied.

When buying a house, your solicitor will normally raise requisitions on title asking the seller to produce planning permission and compliance documents, or, where no permission was obtained, an architect's certificate of exemption, for any extension. If none of this is available and the register shows nothing, it is worth commissioning an independent check with the council or applying for a section 5 declaration to establish the current planning status before completing the purchase.