Building on a sloping site can complicate otherwise straightforward foundations.
Ground levels may differ considerably between neighbouring properties, meaning foundation depths and excavation relationships are not always obvious.
Why does the slope matter?
Section 6 of the Party Wall Act is concerned with the relationship between your excavation and the foundations of neighbouring structures.
Where land levels vary, simply measuring the distance between two buildings may not tell the whole story.
Stepped foundations
Extensions built on sloping land frequently use stepped foundations.
Different parts of the same foundation may therefore be at different depths.
Each relevant section should be considered against the neighbouring structure.
Retaining structures
Changes in ground level may also require retaining walls.
These need careful engineering where they support land close to a neighbouring building or boundary.
Accurate sections are important
Plans alone may not be enough to understand a sloping site.
Sectional drawings showing:
- existing ground levels;
- proposed ground levels;
- foundation depths;
- neighbouring buildings; and
- relevant distances
can make the Party Wall assessment much clearer.
See our guide to Party Wall Notice drawings for further guidance.
The six-metre rule
Deep excavation on sloping ground may also bring the Section 6 six-metre rule into consideration.
Our Section 6 Party Wall guide explains both excavation tests.
Simple Survey can review the geometry
If your property sits on sloping ground, send us the plans and sections.
Visit our Party Wall service page and we can establish which notices are likely to be required.