Building a wall wholly on your land
Under Section 1(5), you can generally build a new wall on your own land up to the line of junction, subject to the applicable legal requirements.
You must normally give the adjoining owner at least one month's Notice.
Their consent is not ordinarily required simply to build the wall wholly on your land, although a dispute about relevant matters may require determination under the Act.
Building a new party wall astride the boundary
If you want a new wall to sit partly on your land and partly on your neighbour's land, Section 1(2) applies.
You must serve the appropriate Notice, and the adjoining owner's written consent is required for construction astride the boundary.
If they don't consent within the relevant 14-day period, you cannot use the Act to force construction of the new wall across the boundary.
You may instead need to design the wall wholly on your land.
Building at the boundary
Illustrative diagram — not to scale.
What about the foundations?
A new wall built wholly on your land may have projecting foundations beneath adjoining land where the Act permits.
However, special foundations involving reinforced structural arrangements cannot be placed on adjoining land without the required written consent.
The actual foundation arrangement should be reviewed before construction.
Projecting foundations at the boundary
Illustrative diagram — not to scale.
Who determines the boundary?
The Party Wall Act doesn't establish ownership of land or determine the precise position of a disputed boundary.
Your architect should prepare drawings showing the proposed construction relative to the assumed boundary.
Where the legal boundary is genuinely disputed, separate advice may be necessary.
What should you do next?
Send us your proposed extension drawings, including wall and foundation details, and we'll review the likely Party Wall requirements.
Related guide: Party Wall Notice for an extension
