The short answer
For underpinning the rear external walls of a ground-floor flat, the likely route is section 6 (adjacent excavation), and the freeholder should usually be served. The upstairs leaseholder should also be considered, especially where their flat is supported by the structure being underpinned or their lease gives a relevant interest.
Why it matters
The freeholder owns the building structure and land, including the external walls and foundations, so a section 6 notice is likely if the excavation is within 3 metres and to a lower depth than an adjoining structure’s foundations. The upstairs leaseholder may also need serving where their flat is supported by the structure being underpinned or their lease gives a relevant interest, although the boundary between flats is usually the floor or ceiling. Where the rear wall is not a party wall and no party structure is cut into, sections 2 and 3 may not apply, and section 6 is the likely route. The lease should always be checked: sometimes the structure is retained by the freeholder, sometimes leaseholders have enough interest to be adjoining owners.
What to do now
- Serve the freeholder, and consider serving the upstairs leaseholder where their flat is supported or their interest is affected.
- Check the lease and building layout before serving.
- Serve a section 6 notice at least one month before excavation, with plans and sections showing the site and depth.
- Where interests are unclear, serve too widely rather than miss a relevant adjoining owner.
Common mistakes
- Serving only the freeholder when the upstairs leaseholder also has a relevant interest.
- Assuming a non-party rear wall means the Act does not apply (section 6 may).
- Serving without checking the lease.
When to call Coburns
If you are underpinning a flat, send us the addresses and lease details and we will confirm who to serve and under which section.