The Party Wall Act and Garden Rooms in London

Check the work, not the distance alone

The Party Wall etc. Act 1996 can apply when you build a wall on the line of junction, work on an existing party wall or party structure, or excavate near a neighbour’s building below specified foundation levels. A freestanding room beside a fence does not automatically need notice. A timber fence itself is not a party fence wall under the Act.

The government’s explanatory booklet sets out the categories and example notices.

The three- and six-metre excavation tests

Under section 6, notice may be required where excavation within three metres of an adjoining owner’s building or structure goes deeper than the bottom of its foundations. A separate six-metre test uses a 45-degree plane from those foundations. The distance alone does not decide the question; the excavation depth and neighbouring foundation level matter.

Ask the foundation designer to mark the neighbouring structure, proposed excavation and levels on a drawing. If the information is uncertain, a party wall surveyor can advise before ground works are scheduled.

Allow time for a valid notice

Where the Act applies, follow the correct notice procedure before work starts. The type of work affects the notice period and the information to provide. Your neighbour’s response can lead to written agreement or a surveyor-led award. Planning permission and building-control approval do not replace this process. The GOV.UK party walls guide gives the practical starting point.

What your installer should put in the brief

Ask for the exact foundation method and depth, the room’s position relative to the boundary, and any proposed work to a shared wall. Identify who will arrange advice or notices and how a change to foundations affects the programme. For planning and building-control checks, see our separate approvals guide.