Party Wall Agreement Explained: Costs, Notices and Process
When the Party Wall Act applies to an extension or loft conversion, which notice to serve and when, what surveyors cost, how an award works, and what to do if your neighbour does not reply.
Key takeaways
- You must give notice under the Party Wall etc. Act 1996 before work to a shared wall, a new wall on the boundary or nearby excavation.
- Party structure notices need two months' notice; boundary walls and excavation need one month.
- If your neighbour consents in writing, there is no surveyor cost; if not, an award typically costs £700 to £3,500 per neighbour.
- The building owner normally pays both surveyors' fees.
On this page (16 sections)
- What is a party wall agreement?
- When do you need a party wall agreement?
- What does not need a notice
- The process step by step
- What if your neighbour does not respond?
- Can you serve a party wall notice yourself?
- What happens if surveyors cannot agree?
- How much does a party wall agreement cost?
- How long does the party wall process take?
- Your rights during the work
- Party wall notices for common projects
- What happens if you do not serve notice?
- How to keep your neighbours on side
- Choosing a party wall surveyor
- Common mistakes
- Party walls in Southampton and Portsmouth
A party wall agreement is the written consent, or surveyors' award, that lets you carry out work covered by the Party Wall etc. Act 1996 in England and Wales. You need one before work to a shared wall, a new wall on the boundary, or foundations dug close to a neighbour's building, and you must serve notice one to two months before that work starts. If your neighbour consents in writing it costs nothing; if they dissent, surveyors typically charge £700 to £3,500 per neighbour, and the person doing the work usually pays.
Most extensions and loft conversions on semi-detached and terraced houses trigger the Act somewhere, usually through steel beams bearing on the party wall or extension foundations near the boundary. This guide explains which notice applies, the timescales, what an award contains, what it costs and how to keep the process from delaying your build.
What is a party wall agreement?
"Party wall agreement" is the everyday name for the paperwork that lets notifiable work go ahead. Strictly, there are two outcomes:
- Written consent. Your neighbour (the "adjoining owner") agrees to the work in writing after receiving your notice.
- A party wall award. If they dissent, one or two surveyors prepare an award: a legal document setting out what work will be done, how and when, with a record of the condition of the neighbour's property before work starts.
The Act applies in England and Wales and covers three kinds of structure: walls shared between two buildings (party walls), masonry garden walls that sit across a boundary (party fence walls), and floors and ceilings between flats.
2 months
Notice for work to a shared wall
1 month
Notice for boundary walls and excavation
14 days
For your neighbour to respond
12 months
Before an unused notice lapses
When do you need a party wall agreement?
You need one when work falls under section 1, 2 or 6 of the Act: a new wall on the boundary, work to a shared wall, or excavation near a neighbour's foundations.
Party structure notice (sections 2 and 3): work to a shared wall
The work is listed in section 2 of the Act; the notice is served under section 3.
Most loft conversions and many renovations involve work to the party wall itself, for example:
- Cutting into the wall to take the bearings of steel beams, the most common trigger for a loft conversion
- Inserting a damp-proof course into the shared wall
- Raising the height of the wall, or thickening it
- Cutting away chimney breasts or projections from the shared wall
- Underpinning or demolishing and rebuilding the wall
Notice period: at least two months before the work starts.
Line of junction notice (section 1): a new wall on the boundary
Building a new wall astride or right up against the boundary line, often the flank wall of a side or rear extension. Notice period: at least one month.
Notice of adjacent excavation (section 6): the 3 metre and 6 metre rules
Digging foundations within 3 metres of your neighbour's building and deeper than the bottom of their foundations, or within 6 metres if the dig would cut a 45 degree line drawn down from the bottom of their foundations. Extension foundations, basements and piling often fall into this. Notice period: at least one month.
What does not need a notice
Everyday work that does not affect the structure of the shared wall is outside the Act: replastering, putting up shelves or kitchen units, adding or replacing most electrical sockets and fixing plasterboard to the wall. If you are not sure, ask before you start rather than after.
The process step by step
- 1
Talk to your neighbourBefore notice
Explain the work and show them the drawings before the formal notice arrives.
- 2
Serve the notice1 to 2 months before work
A written notice naming the owners, describing the work and giving the start date, with drawings for excavation.
- 3
Neighbour respondsWithin 14 days
They consent, or dissent and either agree one surveyor or appoint their own.
- 4
Schedule of condition1 to 3 weeks
The surveyor photographs and records the condition of the neighbour’s property.
- 5
Award agreed and served2 to 6 weeks
The award sets out the method, hours, access and how any damage is put right. Either side can appeal within 14 days.
- 6
Work startsWithin 12 months
Build to the award; surveyors can revisit if a dispute arises during the work.
Every notice must go to each owner of the neighbouring property. Under section 20, "owner" includes anyone with a lease of more than a year, so flats and let houses can mean several notices. A notice of adjacent excavation must include drawings showing the excavation. A surveyor typically charges £100 to £300 per notice to prepare and serve it.
What if your neighbour does not respond?
If your neighbour does not reply within 14 days to a party structure notice (section 2) or a notice of adjacent excavation (section 6), a dispute is treated as having arisen, even if they have no objection. You then send a further written request asking them to appoint a surveyor. If they still do not appoint one within 10 days, you can appoint a surveyor on their behalf, and the process continues to an award. For a line of junction notice (section 1), no reply means you can only build the new wall wholly on your own land.
Can you serve a party wall notice yourself?
Yes. There is no requirement to use a surveyor to serve notice, and the government's explanatory booklet and template notices set out what each notice must contain. Serving it correctly matters: a notice with the wrong section, missing owners or no drawings can be invalid and restart the clock.
What happens if surveyors cannot agree?
Under section 10, the two appointed surveyors select a third surveyor at the start of the process, who decides any point they cannot agree. Either owner can appeal an award to the county court within 14 days of it being served.
How much does a party wall agreement cost?
A party wall agreement costs nothing if your neighbour consents in writing, and typically £700 to £3,500 per neighbour if surveyors are needed.
| Scenario | Typical cost per neighbour (2026) |
|---|---|
| Neighbour consents in writing | £0 (or £100 – £300 if a surveyor serves the notice) |
| One agreed surveyor for both sides | £700 – £1,800 |
| Two surveyors, one each | £1,500 – £3,500 in total |
| Complex work, basements or a third surveyor | £3,500 – £5,000+ |
These ranges are based on published 2026 surveyor fee guides, including BestBuilders' party wall surveyor cost guide, last checked in October 2026; complex jobs cost more. The building owner normally pays all of these. On a mid-terrace house you have two neighbours, so the cost can double. Allow for it in your project budget from the start: on a typical loft conversion budget it is often the single biggest fee after the drawings.
How long does the party wall process take?
With consent, you can start once the notice period has run, which is two months for party structure work and one month for the other two. If surveyors are involved, allow another four to eight weeks for the schedule of condition and the award. In practice, the safest plan is to serve notices as soon as your drawings and structural calculations are ready, at the same time as you apply for planning or a Lawful Development Certificate, so the party wall process runs in parallel instead of delaying the start.
A party wall notice lapses if the work it covers does not start within 12 months of the notice being served, so time your notices to the build. An award covers the work it describes for the length of that work; if the scope changes significantly, a new notice or an addendum to the award may be needed.
Your rights during the work
The Act gives the building owner rights as well as duties. You can enter your neighbour's land to carry out the notified work after giving 14 days' notice (section 8), for example to put up scaffolding or rebuild the face of a party fence wall. You must make good any damage, avoid unnecessary inconvenience and, where the surveyors agree it is needed, provide security for expenses (section 12). Your neighbour cannot unreasonably refuse access once an award is in place.
Section 7 also means you cannot place special foundations, such as reinforced concrete footings, on your neighbour's land without their written consent, and you must compensate them for any loss or damage the work causes.
Party wall notices for common projects
Most extensions and loft conversions on attached houses need at least one notice; this table shows which.
| Project | Notice usually needed | Why |
|---|---|---|
| Rear dormer loft conversion on a terrace or semi | Party structure notice (section 2), two months | Steel beams cut into the party wall |
| Hip-to-gable loft conversion on a semi | Party structure notice, two months | Work to or raising the shared wall |
| Single-storey rear extension near the boundary | Adjacent excavation notice (section 6), one month | Foundations within 3 metres and deeper than the neighbour's |
| Extension wall built on the boundary line | Line of junction notice (section 1), one month | New wall astride or against the boundary |
| Removing a chimney breast on a shared wall | Party structure notice, two months | Cutting away part of the party wall |
| Inserting a damp-proof course in a shared wall | Party structure notice, two months | Work to the party wall |
| Replastering, shelves, most sockets | None | Not notifiable work |
What happens if you do not serve notice?
It is not a criminal offence, but it is a costly shortcut. Your neighbour can apply to the court for an injunction stopping the work until the process is followed, which can leave a half-finished extension under a tarpaulin for weeks. You also lose the record of the neighbour's property before work began, so any crack that appears later is far harder to defend. And a buyer's solicitor may ask about it when you sell.
How to keep your neighbours on side
Most party wall disputes come from surprises, so early, open communication is the cheapest way to avoid surveyor costs.
- Talk to them before the notice arrives. A letter out of the blue is more likely to be dissented to than one that follows a conversation over the fence.
- Show them the drawings and explain what the work involves, how long it will take and how noise and dust will be managed.
- Offer a schedule of condition anyway. Photographing their side before work starts reassures them and protects you, even when they consent.
- Use a builder who has done it before. Most disputes come from surprises: work starting earlier or reaching further than the notice said.
Choosing a party wall surveyor
Any surveyor can act under the Act, but you want one who handles party wall matters regularly. Members of the Faculty of Party Wall Surveyors or RICS-regulated firms are a sensible starting point. If your neighbour is willing, an agreed surveyor acting for both of you is the quickest and cheapest route. If they want their own surveyor, that is their right, and you still normally pay that surveyor's reasonable fees.
Common mistakes
These five mistakes cause most party wall delays and disputes.
- Starting work before the notice period has run. Even a few days early gives your neighbour grounds for an injunction.
- Serving the wrong notice. Excavation, boundary walls and party structure work each have their own notice and timescale.
- Forgetting the second neighbour. On a mid-terrace both sides may need notices.
- Leaving it until the builder is booked. Two months' notice plus a possible award can push the start date back.
- Treating a verbal okay as consent. Consent must be in writing to count.
Party walls in Southampton and Portsmouth
With so many Victorian and Edwardian terraces and 1930s semis across Southampton and Portsmouth, party wall notices are part of most extensions and loft conversions to terraces and semis. Our teams for house extensions in Southampton and loft conversions in Southampton handle them as part of the project. We help you prepare and serve the notices early, alongside planning, so they do not hold up the start date. For the planning side, see our guide to planning permission for a house extension.
Planning an extension or loft?
We survey your home, explain whether party wall notices are needed and help you serve them early, then give you a detailed written quote for the whole project. The survey is free.
Written by
The Pure Renovation & Design team
A Southampton design-and-build company whose team has 18 years of hands-on experience in extensions, loft conversions, full renovations, bathrooms and joinery across Hampshire. Prices are cross-checked against published UK trade cost guides and official fee schedules, and reviewed whenever prices or rules change.
Last reviewed 13 October 2026 · About the team
Our service
House Extensions Southampton
Rear, side return, wrap-around and double-storey extensions, designed, approved and built by one in-house team.
