Planning exemptions in Northern Ireland

Extending without planning, 5 rules every homeowner should know

In this article, we cover:

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Rules of thumb to know if you can extend without seeking planning permission
How to know for sure if your project is planning exempt
Links to relevant documents and regulations

There are many rules to building an extension that doesn’t require planning permission, and you must abide to all of them. So if there’s only one piece of advice to give, that is to get design professionals involved to ensure that your proposed extension can be considered exempted/permitted development.

Then obtain confirmation from your local authority’s planning department through a Certificate of Lawful Development.

1. The house extension must not take up too much room on the site.

The rules state that the ground area covered by the extension and any other buildings within the boundary of the property, excluding the original house, is not more than half the total area of the property.

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2. The house extension must not be too high

Any part of the extension is not higher than the highest part of the roof of the existing house. The eaves should be no more than three metres in height if any part of the extension is within two metres of the property boundary.

3. The house extension must not be too big

The rules work on the basis of distance rather than area; a single storey extension should not extend beyond the rear wall of the original house by more than four metres for a detached house or three metres for any other type of house. In both cases the height of the extension must not exceed four metres. And for an extension of more than one storey the extension should not extend beyond the rear wall of the original house by more than three metres.

4. The house extension must not project further than the ‘principal elevation’ of the house

For example, you would not be able to add a bay window to an existing house without planning permission as it projects further than the principal elevation. Small porches are however allowed under certain circumstances.

The regulations state: “Any part of the extension does not extend beyond any wall facing road if it forms the principal or side elevation of the original house.” This implies that you are allowed to build a planning exempt extension to the side of the house as long as it doesn’t project
further than the principal elevation.

5. The house extension must respect your neighbours’ privacy

Something that is incredibly important and is often overlooked is that if you have constructed a flat roof extension, you are not allowed under permitted/exempted development to use that roof as a balcony with handrails. This is because it can easily lead to issues with overlooking and privacy.

In addition to the eaves height requirement, no part of a single storey extension can be within 3.5 metres of any property boundary with a road opposite the rear wall of the house. In an extension with more than one storey; no part of the extension can be within seven metres of the property boundary opposite the rear wall of the house.

An upper floor window on a side elevation within 15 metres of a boundary with another house must be obscure glazed; and be non-opening unless the parts which can be opened are more than 1.7 metres above the floor of the room in which the window is installed.