Line of junction notices for new boundary walls

When you plan a new wall at the boundary between two properties, the line of junction rules in section 1 of the Party Wall etc. Act 1996 may apply. The correct approach turns on where the wall is positioned. A wall placed across the boundary is treated differently from one built entirely on the building owner's land.

Two different situations under section 1

1. A wall astride the boundary: section 1(2)

If you want to build a party wall astride the line of junction, you must serve notice and obtain the adjoining owner's express written consent to building astride the boundary. A lack of reply is not the consent needed to place your wall on their land. The Act sets out a 14-day period for that consent. Where it is not given, the wall cannot simply be built across the line as originally proposed.

2. A wall wholly on your own land: section 1(5)

Where you propose to build a wall placed wholly on your own land at the line of junction, section 1(5) requires a notice at least one month before starting. This route is not a way to bypass ownership of the boundary: you need to be clear where the line actually is. The Act also contains specific provisions concerning foundations and compensation.

What should the notice say?

Identify the building and adjoining owners, the two properties, the proposed boundary wall and its position relative to the line of junction. Describe the intended wall clearly, including its approximate height, length and materials where known. A straightforward drawing can help neighbours understand the proposal even when particular section 1 drawings are not mandatory.

GOV.UK has separate official sample letters: Example Letter 4 for a wall astride the boundary, and Example Letter 6 for a wall wholly on your own land. The two are not interchangeable.

Example: a garden extension wall

Suppose a new single-storey rear extension includes a side wall near the property boundary. If your proposed wall is entirely on your land, a line-of-junction notice may be relevant. If you instead want its thickness to cross the boundary, you need the adjoining owner's express written consent for that arrangement. Separately, excavation for the foundations could raise a section 6 notice question: the notices serve different purposes.

What if the neighbour says no?

Distinguish an objection to the overall building project from refusal to allow a wall to cross the boundary. For a wall astride the line, you cannot assume permission and carry on across the boundary. For a wall wholly on your land, questions about boundary location, foundations, damage or statutory rights may still need attention. If there is an actual dispute under section 1, the Act refers disputes to its section 10 procedure.

Checklist before you serve

• Confirm the boundary location; do not rely solely on a rough online map.
• Ask the designer whether the wall is astride the line or entirely on one side.
• Prepare a clear description of the wall, position and planned start date.
• Identify the relevant adjoining owners and keep records of service.
• Check whether excavation or work to an existing party structure requires a separate notice.

Further reading: boundary wall guidance, extensions, and notice periods.