Why they are treated differently
Reinforced foundations under a neighbour's land can make it harder and dearer for them to build there later, so the Act gives the neighbour a veto.
When they come up
- Footings projecting under the neighbour's land for a new wall on the boundary
- Underpinning that extends beneath the party wall
- Engineered foundations for basements or heavy extensions
What the notice must include
If a party structure notice proposes special foundations, it must include plans, sections and construction details, with reasonable particulars of the loads they will carry.
If the neighbour consents
They can serve a counter notice asking for the foundations to go deeper, or be made strong enough for a building of their own, or both. And if the foundations later add to the cost of the neighbour's own building work, the owner of the foundations can be required to repay the extra.
If they do not
The design has to keep reinforced foundations on the building owner's own land, for example with an eccentric or cantilevered footing. Tell your engineer before they design.
Common questions
Is a plain concrete strip foundation a special foundation?
No. Concrete without steel reinforcement is not a special foundation.
Where this comes from in the Act
- Section 1: New building on line of junction
- Section 3: Party structure notices
- Section 4: Counter notices
- Section 7: Compensation etc.
- Section 11: Expenses
- Section 20: Interpretation
Links go to the official text of the Party Wall etc. Act 1996 on legislation.gov.uk.