Do I have to notify the neighbours about my extension?

Now that you have agreed upon a proposed scheme with your Architect, it is essential to know if your neighbour(s) need to be told about your plans. If they do, you have a legal duty to notify them about what you are planning to do.

Just a heads up, the rubber meets the road with part wall affairs and the particulars can get quite technical, but here are the circumstances[1] under which notifying the neighbours will be necessary:

• Inserting a damp proof course, even if you are only doing so to your side of the wall;
• Cutting into the neighbouring wall to weather-proof compromised joints and junctions;
• Increasing the thickness of a party wall (where doing is deemed to have a material impact on the neighbouring side);
• Taking down and rebuilding a party wall;
• Underpinning the whole or a section of the party wall;
• Works that necessitate cutting into the party wall for the installation of structural members;
• Building a new storey above the boundary line;
• Constructing a new wall on the boundary line between you and the neighbour(s);
• Digging foundations (or excavations as they are referred to in the party wall world), if those excavations: (a) lie within 3 meters of the boundary; (b) are deeper than your neighbour(s) foundations, or (c) are within 6 meters of a neighbouring building if a line can be drawn at a 45-degree angle between the bottom of your foundation to that of the neighbours’.

Minor work involving the party wall, such as re-wiring, chasing channels for utilities, plastering, decorating or hanging pictures and such like, and deemed to be de minimis and so do not require you to notify the neighbours.

If your extension ticks any of the notifyable criteria, you have a legal obligation to tell the neighbour(s) about your extension. The technical term for this is called serving notice. In short if you want to make your home bigger and are attached to (or are in close proximity to) another property, you will most likely need to notify the neighbour(s) about your extension.

[1]Your Wall Or Mine, Dil Gujral Feb 2019