Rear extensions
Almost all rear extensions trigger Section 6 because the new foundations are deeper than the neighbour's existing footings. If the extension also touches a party wall (most do), Section 3 is also triggered. You can serve both notices together.
Loft conversions
Loft conversions almost always need a Section 3 notice. Steel beams need pockets cut into the party wall, dormer cheeks may sit on top of the party wall and flashings often involve cutting in. Two months notice is required.
Garden walls and fences
A freestanding garden wall under two metres on your own land does not need notice. A wall built on the boundary needs a Section 1 notice. A wall taller than two metres needs careful consideration — height is not the only test, position is.
Internal works only
Painting, decorating, replastering, replacing kitchens or bathrooms — none of these need a Party Wall notice as long as they don't disturb the structure of a shared wall.
Basement conversions
Almost always trigger both Section 3 (underpinning) and Section 6 (excavation depth). A surveyor's involvement from day one is strongly recommended.
Garage builds, decking and conservatories
Depends on the foundations, the height and the position relative to the boundary. The free checker walks through these in 60 seconds.
When to call a surveyor
Whenever you are unsure. The eligibility checker is honest about ambiguous cases — we recommend a free 15-minute call with a party wall surveyor rather than guessing.