The short answer
Usually, yes — often on two counts. A two-storey extension generally triggers section 6 through its deeper foundations near the neighbour’s building, and section 2 because the upper floor is frequently tied into, built off, or raises the party wall. You will usually need both a notice of adjacent excavation and a party structure notice before starting.
Why it matters
The upper storey is what sets a two-storey extension apart. Carrying the new floor and roof often means inserting beams into the party wall and bonding new masonry to it — clearly a section 2 work, which needs a party structure notice under section 3, served two months ahead. The foundations are usually deeper than a single-storey, strengthening the section 6 case (one month). You may also build the flank wall on the boundary (section 1). On a terrace, both neighbours can be affected. The award deals with support, method, scaffolding access, protection and a schedule of condition.
What to do now
- If your neighbour does dissent, suggest a single agreed surveyor acting fairly for both of you — cheaper and faster than two. Coburns recommends this wherever possible.
- Get structural and foundation drawings.
- Identify where the new structure meets the party wall.
- Apply the section 6 tests.
- Serve a party structure notice (two months) and an excavation notice (one month) as needed, and allow for the longer period in your programme.
Common mistakes
- Serving only the excavation notice and missing the party structure works.
- Underestimating the two-month party structure period.
- Forgetting scaffolding access over the boundary (section 8).
- Missing a second neighbour on a terrace.
When to call Coburns
Send us your plans and we will identify every notice a two-storey extension needs, serve them free of charge, and set fair access and protection terms in the award.