Party Wall Agreements for Excavation Near Boundaries

Why excavation gets its own set of rules

Digging a foundation, basement or drainage run near a boundary is rarely just your business. Soil supports the structures sitting on it, and when you remove or loosen that soil, your neighbour's walls, footings and garden walls can move. The Party Wall etc. Act 1996 recognises this and gives neighbours specific rights — and you specific duties — whenever excavation work comes close enough to matter.

The key point that catches people out is that the Act does not only apply to shared walls. You can be in scope under section 6 with no party wall in sight, purely because of how close and how deep your excavation is. Get this wrong and you may find yourself dealing with an injunction, a damages claim or a very unhappy neighbour before the first concrete pour.

The three-metre and six-metre rules

Section 6 sets out two triggers, and you need to check both before you break ground.

• Three-metre rule: if your excavation comes within 3 metres of any part of a neighbouring building or structure, and the bottom of your excavation will be deeper than the bottom of that neighbour's foundation, the Act applies.
• Six-metre rule: if your excavation comes within 6 metres of a neighbouring building or structure, and the bottom of your excavation is deeper than the neighbour's foundation, you must also check the 45-degree line. Draw a line down at 45 degrees from the underside of the neighbour's foundation; if your excavation would cross it, the Act applies.

“Structure” is deliberately broad. It takes in houses, extensions, garages, boundary walls, outbuildings and sometimes substantial garden features. Depth matters as much as distance, so a shallow trench 2 metres away is usually fine, while a 2.5-metre-deep basement dig 5 metres away often is not.

Serving notice: what, when and how

If section 6 applies, you must serve a written notice on the adjoining owner. For excavation works the notice period is at least one month before you start (works to a party structure under section 2 require two months). The notice should describe the works, show the intended depth of excavation and, ideally, include a plan and section drawing. Vague notices are a common reason for disputes.

The neighbour then has 14 days to respond. They can consent in writing, which is the cheapest and quickest outcome, or they can dissent. In practice, many parties agree a written consent with conditions attached — a schedule of condition, a method statement, working hours and monitoring — and no formal award is ever needed.

Do remember that a party wall notice is not a substitute for planning permission, building regulations approval, or any licence needed to excavate under a highway.

When a dispute arises — and what an award actually does

If the neighbour dissents, or simply does not reply within 14 days, a dispute is deemed to exist. At that point you move to the surveyor stage. Each side can appoint a surveyor, or you can agree on a single joint surveyor. If two surveyors cannot agree, a third surveyor is selected to make the call.

The result is a party wall award — a legally binding document that usually covers:

• Exactly what works are authorised and the method to be used, including underpinning, piling or temporary support where needed.
• A schedule of condition recording the neighbour's property before work starts, with photographs and sometimes a dilapidations report.
• Working hours, access arrangements, monitoring and notification of key stages.
• Who pays whose fees. The building owner normally pays the adjoining owner's reasonable surveyor costs, along with any making good that proves necessary.

An award does not give you a free hand. It also does not transfer liability for negligence — if your contractor damages the neighbour's property, you remain responsible for putting it right.

Practical tips before the digger arrives

A little preparation saves a lot of grief. Talk to your neighbour early, in person, before the notice lands on the mat. Explain the scope, share drawings and offer a joint condition survey. Most objections come from uncertainty rather than from the work itself.

Check your ground conditions properly. Clay, running sand, gravel and a high water table all change the risk profile, and they may push you towards secant piling, sheet piling or a different sequencing plan. Vibration from piling or compaction equipment travels further than people expect, so agree monitoring thresholds in advance.

Keep a paper trail: dated photographs, signed consents, contractor method statements, insurance certificates. If a crack appears three months later, that file is your best defence.

Keeping the neighbours onside

Party wall procedure can feel heavy for a modest extension, but it exists to protect both sides. Follow it properly and you gain certainty: a clear record of the condition of the neighbouring property, an agreed method of working, and a binding route to resolve disagreements without going to court. Ignore it and you risk an injunction stopping work mid-project, plus the cost of remedial work and legal fees.

If your excavation is anywhere near a boundary and deeper than next door's footings, treat a party wall review as part of your pre-construction checklist — not an afterthought. A short conversation with a party wall surveyor before you tender the groundworks will almost always cost less than the problem it prevents.