Rear extensions are brilliant for creating open-plan living—but they almost always wake up the Party Wall etc. Act 1996. That’s because new foundations, drainage runs, and pad foundations for steels are frequently dug within 3 metres of a neighbour’s wall, house, extension, outbuilding, or other structure. If your excavation will go deeper than your neighbour’s foundations (typical for older housing stock), you must serve a Section 6 (Adjacent Excavation) Notice before works begin.
Below is a clear guide to when notices are required, what responses you can expect, and the protections the Act provides to keep projects lawful, safe and neighbourly.
When do you need a Party Wall Notice for a rear extension?
For rear extensions, the most common trigger is Section 6 (Adjacent Excavation):
- Within 3 metres of any part of a neighbouring building or structure and deeper than the bottom of their foundations.
- Within 6 metres if any part of your deeper excavation intersects a line drawn down at 45° from the underside of the neighbour’s foundation (the “6m/45° rule”).
Typical rear-extension items that trigger Section 6:
- Trench foundations for new masonry walls
- Pad bases for steel columns or goalpost frames
- Deepened foundations for bi-fold openings
- New drainage runs and manholes close to the boundary
Timing: Section 6 Notices must be served at least 1 month before the notifiable excavation starts and must include plans and sections showing the location and depth of the proposed excavation. Notices remain valid for 12 months from service.
Good practice: speak to your neighbour first, then serve the formal notice. Early, friendly communication reduces anxiety and speeds decisions.
How your neighbour can respond
Once served correctly, the Adjoining Owner has 14 days to reply:
- Consent in writing
The work can proceed (you must still follow the Act, work safely, and respect the agreed start date in the notice). - Dissent and appoint an Agreed Surveyor
A single, impartial surveyor acts for both owners to produce a Party Wall Award. - Dissent and appoint their own surveyor
You appoint your surveyor; they appoint theirs. Those two select a Third Surveyor for any deadlocks. - No response
After 14 days, dissent is deemed. You may serve a 10-day request for them to appoint; if they still don’t, you can appoint a surveyor on their behalf under section 10(4) so the process can move forward.
What protections does the Act provide?
The Act isn’t a blocker—it’s a risk-management framework that enables your extension to proceed while protecting both sides. Expect a well-drafted Party Wall Award to cover:
1) Time & manner of working
Clear controls around digging close to a neighbour, e.g.:
- Staged or sequential excavation (short “bays” rather than long open runs)
- Temporary support rules and bearing checks
- Hand tools at sensitive interfaces to reduce vibration
- Sensible working hours for disruptive tasks
2) Methods & safeguards
Awards often reference foundation depths, bearing strata, propping sequences, and temporary waterproofing at the boundary—so the build remains stable and weather-tight throughout.
3) Access—where reasonably necessary
Limited, controlled access can be granted (with notice) to allow safe execution of notifiable works at the boundary—e.g., forming or finishing the flank wall, installing flashings, or making good.
4) Making good / compensation
If notifiable works cause loss or damage, the Award sets the route to make good or payment in lieu—keeping arguments away from the kitchen table and within a clear legal pathway.
5) Impartiality & enforceability
Surveyors act independently under statute. Once served, the Award is binding unless appealed in the county court within 14 days.
Practical tips for rear extensions
- Design depth early. Your engineer should confirm formation levels and bearing strata; those details go into the Section 6 drawings.
- Plan the sequence. Don’t leave the boundary open. Short, braced bays keep ground stable and neighbours reassured.
- Value communication. A pre-notice chat and a realistic programme reduce friction—and often costs.
Keep your rear extension on track—with Simple Survey
We specialise in making the Party Wall process fast, fair, and cost-controlled for rear extensions. You’ll get crystal-clear notices and practical Awards your contractor can follow on site.
Transparent Simple Survey fees
- Party Wall Notice service: £25 per adjoining ownership (multi-notice bundles discounted)
- Act administration as Agreed Surveyor (single surveyor): typically £300 fixed-fee (depends on complexity and number of notices/owners)
- Two-surveyor route (we act for the Building Owner): fixed-fee proposals from £325
(we work to keep your neighbour’s surveyor’s hourly fees reasonable and contained)
Get your Rear Extension PW Fast-Start Pack (free)
Email your sketch or drawings to team@simplesurvey.co.uk. We’ll confirm exactly which notice(s) you need, flag any risk hot-spots around the 3m/6m rules, and propose the quickest route to a robust Award—so you can break ground on time and stay neighbour-friendly.