The short answer
It depends, and a conservatory is less likely to be notifiable than a full masonry extension. The Act only bites if one of three things happens: the foundations are within three metres of a neighbour’s building and dug deeper than their foundations (section 6); a new dwarf or flank wall is built on or up to the boundary line (section 1); or the conservatory is tied into or cut into the party wall, which is party structure work needing a party structure notice under section 3. Because conservatories often sit on shallow bases, the section 6 trigger is frequently not met — but where one is built up to the boundary or against the party wall, notice is needed. Planning permission and permitted development do not change this.
Why it matters
The three triggers apply to a conservatory like this:
- Foundations (section 6) — conservatory bases are often shallower than the neighbour’s foundations, so this is frequently not triggered. But modern orangeries and garden rooms with deeper footings near the boundary can meet it. The test is depth relative to the neighbour’s foundations within three metres (or six metres on the 45° line). One month’s notice.
- Building on the boundary (section 1) — a dwarf wall or frame built on or astride the boundary line is a line of junction matter. One month’s notice.
- Party wall works (section 2; party structure notice under section 3) — fixing the conservatory to, cutting into, or flashing into the party wall. Two months’ notice.
Many lean-to conservatories — built against your own rear wall, on a shallow base, away from the boundary — are not notifiable at all. As a rule of thumb, the closer to the boundary and the deeper the base, the more likely a notice is needed.
What to do now
- Get the base or foundation detail, including the depth.
- Check the distance to each neighbour’s building and apply the section 6 tests.
- Check whether any wall sits on the boundary (section 1) or ties into the party wall (section 3), and serve the right notice if any apply.
- If a surveyor is needed, use one. Both owners can appoint a single impartial ‘agreed surveyor’ rather than one each — quicker, cheaper and less adversarial. Coburns recommends a single agreed surveyor wherever possible.
Common mistakes
- Assuming a conservatory never needs a notice — or assuming it always does.
- Missing a deeper modern base that does trigger section 6.
- Building a dwarf wall on the boundary without a line of junction notice.
- Flashing into the party wall without a party structure notice.
When to call Coburns
Send us your plans and base detail and we will confirm, free of charge, whether your conservatory needs a notice — and serve it if so.