Party Wall Services. Handled by Professional Surveyors.
A party wall notice for extension works is required in most London projects. The Act applies when your extension builds a wall at the boundary, excavates near a neighbour's foundations, or cuts into a shared party wall. Rear and side extensions in London's terraced and semi-detached streets almost always do at least one of these.
Your extension may avoid the Act only if it keeps clear of the boundary, does not touch a shared wall, and does not excavate near a neighbour's foundations. That combination is uncommon in London, so confirm your position early, before your start date is fixed.
In most London extensions, yes. A party wall notice for extension works is needed whenever the project affects a shared wall, the boundary, or a neighbour's foundations, under the Party Wall etc. Act 1996. Most London homes are terraced or semi-detached, so the next structure is rarely more than a few metres away, and a rear or side extension usually digs new foundations close to it or builds up to the boundary.
It helps to separate two things that are often confused. Planning permission and the Party Wall Act are different requirements. Permitted development rights or a planning approval tell you what you may build; they do not remove the duty to serve a notice where the works are notifiable. Both can apply to the same extension at once. If your architect or structural engineer has already raised a party wall point, treat that as a strong sign the Act applies.
Not every part of an extension affects your neighbour, but in most London projects at least one element does. Notifiable extension works fall into three groups.
Building a new wall along or astride the boundary triggers the Act. Served as a Line of Junction Notice under Section 1.
Extension foundations often sit within 3 or 6 metres of a neighbouring structure. Digging deeper than their foundations needs an Excavation Notice under Section 6.
Where the extension cuts into, bonds to, or loads the shared wall, a Party Structure Notice under Section 2 applies.
Many rear extensions trigger more than one at once. A side return that digs new foundations and builds to the boundary, for example, can need two notices, each served on every affected owner.
Extensions almost always need new foundations, and those foundations are what bring Section 6 into play. The Act sets two distance rules, both measured from your neighbour's structure, not from the boundary.
Because London homes sit so close together, a standard rear extension often falls inside the 3 metre rule without the owner realising. Where it does, your project needs a Section 6 excavation notice alongside any boundary or party wall notice.
The notice depends on the work, not the size of the project. A single extension can need one notice or several.
| Type of work | Notice | Minimum notice period |
|---|---|---|
| New wall at or astride the boundary | Line of Junction Notice (Section 1) | 1 month |
| Cutting into or building off the party wall | Party Structure Notice (Section 2) | 2 months |
| Excavating near a neighbour's foundations | Excavation Notice (Section 6) | 1 month |
The notice period runs from the date served, not your planned start date, and these are statutory minimums. A Party Wall Notice stays valid for 12 months, so LENIO generally recommends serving once the structural design and scope are settled, not the week before you break ground.
In London a neighbouring property can have more than one qualifying owner. Notice must reach the freeholder, any leaseholder with more than 12 months left, and any management company or housing association responsible for the building.
The works can proceed once the notice period passes, with no Party Wall Award needed. A Schedule of Condition is still worth arranging to protect both sides if a damage claim arises.
A dispute is deemed to arise and surveyors are appointed under Section 10 to prepare a Party Wall Award covering access, working hours and protective measures. On most extensions this is routine and does not stop the project.
The Act treats silence as a dispute. You serve a further request giving 10 days to appoint a surveyor; if they still do not, you may appoint one on their behalf. Assuming silence means consent is a common, costly mistake.
You are not legally required to appoint a surveyor; the Act lets a Building Owner serve notices themselves. In practice most homeowners use one, because extensions often involve more than one notice and several affected owners, and an invalid notice restarts the clock.
A party wall surveyor confirms which notices apply, identifies every owner who must be served, serves each notice correctly and on time, and where a neighbour dissents, prepares the Party Wall Award and Schedule of Condition. At LENIO every extension instruction is led personally by a Chartered Civil and Building Engineer (ICE and CABE) with direct experience of London's terraced and semi-detached housing.
Often yes. A single-storey rear extension usually digs new foundations near the neighbouring property and may build up to the boundary, both of which are notifiable. In London's terraced streets the 3 metre rule catches most of them. A quick review of your drawings confirms the position before you commit to a start date.
Usually yes. A side return often builds a new flank wall at or near the boundary and excavates new foundations beside the neighbouring house, which commonly triggers a Line of Junction Notice, an Excavation Notice, or both. The exact notices depend on where the new wall sits relative to the boundary line.
Almost always. A two-storey extension usually cuts into the party wall at first-floor level and digs deeper foundations near the neighbour, so a Party Structure Notice and an Excavation Notice often apply together. A surveyor confirms exactly which once the structural drawings are ready.
No. The statutory notice period must run in full before notifiable works begin, unless your neighbour agrees in writing to an earlier start. Starting early risks an injunction and undermines the protection the process gives both sides, so the notice period needs to sit in your programme from the outset.
Yes. Every Adjoining Owner affected by the works is entitled to their own notice and response period. A mid-terrace extension can affect neighbours on both sides, and in flats or converted houses more than one owner of a single property may need a notice.
It depends on the scope, the number of notices, and how many neighbours are involved. A straightforward extension with a single notice costs less than one needing several notices or a Party Wall Award. LENIO gives a clear quote after reviewing your drawings, and initial advice is free.
Send us your drawings or a short description of the works. A LENIO chartered surveyor will confirm which notices apply, who must be served and when, with free initial advice and no obligation.
