Nauman Zafar | Party Wall Consultant | Survey of Party Wall · Last Updated: June 2026 · Reviewed against the Party Wall etc. Act 1996 and Pyramus & Thisbe Club best practice
Rear Extension Party Wall Costs by Scenario
| Scenario | Neighbours | Typical Cost 2026 |
|---|---|---|
| Neighbour consents, schedule of condition only | 1 | £350 to £600 |
| Agreed surveyor, single award | 1 | £900 to £1,600 |
| Separate surveyors | 1 | £1,600 to £2,500 |
| Agreed surveyor | 2 | £1,400 to £2,300 |
| Separate surveyors, both dissent | 2 | £2,500 to £4,200 |
A standard single storey rear extension on a London terrace triggers Section 2 of the Act where the new wall cuts into or bears on the party wall, and Section 6 where foundations go within 3 metres of the neighbouring building and below their foundation depth. On Victorian terraces with foundations at 600mm to 900mm, almost every rear extension triggers Section 6.
What the Fee Covers
The schedule of condition is the part you should never cut. In Taylor v Jones [2024] EWCA Civ 170 the Court of Appeal confirmed the schedule of condition is the primary evidence separating pre-existing damage from damage caused by your works. Without one, you cannot prove a crack in your neighbour’s kitchen was there before your builder started.
The 3-Metre Rule on Rear Extensions
Read the full breakdown in our 3 metre rule guide and the complete party wall surveyor fees London guide.
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Three Scenarios
Representative illustrative scenarios. Not named clients. Indicative 2026 figures.
Scenario 1, lowest cost. Mid terrace in Lewisham, one affected neighbour, informal conversation before notices, neighbour agreed to an agreed surveyor. Notice, schedule of condition and award completed in five weeks. Illustrative total: £1,150.
Scenario 2, both sides dissent. Mid terrace in Walthamstow, extension touching both party walls. Both neighbours dissented and appointed separate surveyors. Three surveyors in total, awards agreed in eight weeks. Building owner paid all fees under Section 10(13). Illustrative total: £3,600.
Scenario 3, no schedule of condition. A homeowner accepted a consent letter and skipped the condition record to save £450. A crack appeared in the neighbour’s hallway during groundworks. With no pre works record the homeowner could not prove it was pre-existing and paid for redecoration. The £450 saving cost £1,800.
Key Takeaways
- Rear extension party wall costs run £900 to £4,200 in London depending on neighbours and surveyor arrangement
- The building owner pays all reasonable fees under Section 10(13), including the neighbour’s surveyor
- An agreed surveyor saves 25 to 35% and completes faster
- Never skip the schedule of condition. Taylor v Jones [2024] made it the deciding evidence in damage disputes
- Instruct your surveyor 12 to 16 weeks before your builder’s start date
Frequently Asked Questions
Do I need a party wall agreement for a rear extension?
Almost certainly yes on a terraced or semi detached London property. Foundations within 3 metres of the neighbouring building trigger Section 6, and any work cutting into the shared wall triggers Section 2.
Who pays the party wall surveyor for a rear extension?
The building owner pays all reasonable fees under Section 10(13) of the Act, including the adjoining owner’s surveyor if they appoint their own.
Can my neighbour stop my rear extension?
No. The Act is an enabling act. A dissent triggers the surveyor process, which produces a binding award allowing works to proceed under agreed conditions.
How long does the process take?
Six to ten weeks from notice to award with a cooperative neighbour. Add the statutory notice period and allow 12 to 16 weeks total from instruction.
