This is one of the most searched — and most misunderstood — questions in the whole party wall world. The confusion comes from one word: "agreement". Most people who search for a party wall agreement actually need a party wall notice, and the difference is worth thousands of pounds.
Notice vs agreement: the crucial difference
- A party wall notice is the formal letter you serve on your neighbour before starting notifiable works. Almost every extension that touches the boundary or digs near next door needs one. Cost: from £30 with us, or free if you draft it yourself (with the risks that carries).
- A party wall "agreement" — properly, a Party Wall Award — is the formal document surveyors produce only if your neighbour dissents to the notice. Cost: typically £900–£2,700 in surveyor fees.
You can't skip the notice and go straight to an agreement, and you don't need an award if your neighbour consents to the notice. Around 45% of notices end in consent — no award, no surveyors, no four-figure bill.
Does a small extension need a notice at all?
It depends on three questions, not on the size of the extension:
- Are you building on or up to the boundary line? A flank wall on or astride the line of junction needs a Section 1 notice — one month before starting.
- Are you cutting into or working on a shared wall? Inserting steel beams, removing a chimney breast, raising or thickening the party wall — that's a Section 3 notice, two months before starting.
- Are you digging within 3 metres of next door's building, deeper than their foundations? Standard strip foundations for even a small rear extension usually are — that's a Section 6 notice with drawings, one month before starting.
A two-metre-deep "small" extension with normal foundations, one metre from the neighbour's kitchen wall, is notifiable. A large detached garden room ten metres from any boundary isn't. Size is irrelevant; proximity and depth are everything.
What most small extensions actually involve
The typical case: a single-storey rear extension in a terrace or semi. That usually means a Section 6 notice to each attached neighbour (for the foundations), sometimes a Section 1 or Section 3 notice too, depending on where the new wall sits. Notices served, a friendly chat beforehand, neighbour consents within 14 days, works start after the notice period. Total party wall cost: the price of the notices.
If a neighbour dissents, don't panic — propose a single Agreed Surveyor and the award process stays proportionate. Read our guide to consent vs dissent for what each response means.
Unsure which side of the line your project falls? The free 60-second checker will tell you — and if you need notices, generate them here from £30 each.