Do I need planning permission?

What exempted development is

Exempted development is set out in Schedule 2 of the Planning and Development Regulations 2001, a long schedule of classes running from gates and walls to agricultural buildings. Three of them account for most work on a house: Class 1, extending it; Class 3, a garden room, shed or garage; and Class 3A, a detached house in the rear garden. Each class carries its own conditions, and work that breaches any one of them needs permission.

The limits moved in 2026. The Planning and Development (Exempted Development (Act of 2000)) Regulations 2026 substituted Class 1 and Class 3 with effect from 27 July 2026, and a companion instrument inserted Class 3A on the same date. Guidance published before then quotes the older figures, so it is worth checking the date on anything you read. Both checkers apply the current text, and each page says which instrument its figures come from.

What the checkers do not decide

They test the limits that can be worked out from dimensions. They cannot see where your windows face, what shape your roof is, whether the house is a protected structure or in an Architectural Conservation Area, or what conditions were attached to the permission your estate was built under. Any of those can remove the exemption on its own, and none of them is visible to a calculator.

Where certainty matters, a local authority can issue a formal declaration under Section 5 of the Planning and Development Act 2000 confirming whether a proposal is exempt. Preparing that application is part of what we do, as is the full planning application where the work goes beyond what is exempt.