Party Wall Checklist for London Extensions: What You Need to Do

Party wall matters are one of the most commonly misunderstood aspects of building an extension or loft conversion in London. Getting the party wall process wrong — particularly failing to serve notices in time — can cause significant delays, legal exposure, and neighbour disputes. This checklist helps you understand what needs to happen and when.

Step one is to identify whether the Party Wall etc. Act 1996 applies to your project. The Act applies to: (a) work on an existing party wall or party structure (a wall shared with a neighbour, or a wall on the boundary), (b) new building on or at the boundary of your land, and (c) excavations within three metres of a neighbouring building to a depth below its foundations, or within six metres of a neighbouring building to a depth below a 45-degree line from the base of its foundation. Most London rear extensions and loft conversions trigger the Act on at least one of these grounds.

Step two is to identify the adjoining owners who must receive notice. An adjoining owner is any person who owns or occupies land within the above distances. This may include neighbours at the rear (particularly where excavations extend close to their garden building or wall), as well as neighbours to the side (party wall).

Step three is to serve the correct type of notice at the correct time. For work on an existing party wall, a party structure notice must be served at least two months before the proposed start date. For new building at the boundary, a line of junction notice must be served at least one month before start. For excavations, an adjacent excavation notice must be served at least one month before start. Notices must be in writing and must contain specific information required by the Act.

Step four is to wait for responses. Each adjoining owner has fourteen days to respond. They may consent in writing (allowing work to proceed under the notice), dissent (which triggers the surveyor process), or fail to respond (treated as dissent after fourteen days).

Step five: if consent is not received, appoint surveyors. You must pay for an agreed surveyor (agreed by both parties) or for two surveyors (one for each party) if they cannot agree on a single surveyor. You pay for both surveyors as the building owner.

Step six: the surveyors agree a party wall award. The award sets out the work, the conditions, and a schedule of condition of the neighbouring property. This is the document that governs the works and protects both parties.

Step seven: the award is issued. Work may begin after the award is served on both parties (or after a period specified in the award). If either party disagrees with the award, they have fourteen days to appeal to the County Court.

Timelines: allow six to twelve weeks from service of the first notice to receipt of an agreed award. Include this in your project programme — starting work before the award is issued is unlawful and can result in an injunction and having to undo completed work.

RCB includes party wall timing in our pre-construction planning as standard for all London projects. +44 7359 872594 | connect@rcbGroup.co.uk | www.rcbGroup.co.uk