The short answer
Often, yes. Section 6 of the Party Wall etc. Act 1996 covers excavation near a neighbour’s building. If you dig within three metres of their structure and go deeper than the underside of their foundations, or within six metres where a line drawn down at 45° from the base of their foundations would be cut by your excavation, you must serve a notice of adjacent excavation one month before — with plans and sections showing the depth. This applies even to detached houses.
Why it matters
Foundations for extensions, basements, underpinning and even some landscaping can engage section 6. The two tests — three metres and deeper than their foundations, or six metres on the 45° line — exist to protect the neighbour’s building from being undermined. The notice must show the depth and position so the adjoining owner’s surveyor can assess the risk, and the award can require particular methods, monitoring, and sometimes security for expenses on riskier digs. Being detached does not make you exempt — it is proximity to the neighbour’s building that counts.
What to do now
- You can both appoint one agreed surveyor instead of one each — the impartial, lower-cost route Coburns recommends.
- Get your foundation and section drawings showing the proposed depth.
- Measure the distance from your excavation to the neighbour’s building.
- Apply both the three-metre and the six-metre / 45° tests.
- Serve a section 6 notice one month before, with the plans and sections.
- Expect questions about method and monitoring on deeper excavations.
Common mistakes
- Checking only the three-metre test and forgetting the six-metre / 45° one.
- Serving without depth drawings.
- Assuming a detached house is exempt.
- Starting before the one-month period is up.
When to call Coburns
Send us your foundation drawings and we will apply the section 6 tests, prepare the notice with the right plans and sections, and serve it free of charge.