Guide

Party wall notices and agreements for extensions, loft conversions and basements

KRAMAN Ltd. Published 29 October 2026. Rules checked on 29 October 2026 against the government booklet and the Act listed under Sources below.

If your building work touches a wall you share with a neighbour, builds a new wall on the boundary or digs close to a neighbour's foundations, the Party Wall etc. Act 1996 requires written notice to the neighbour before work starts. The notice period is at least two months for work on a party wall and at least one month for a new boundary wall or an excavation. If the neighbour agrees in writing, no surveyor is needed. For party wall work and excavations, a neighbour who objects or does not reply within 14 days creates a dispute, and surveyors then draw up an award, the document most people call a party wall agreement. A new wall on the boundary follows its own rules, set out below.

Which work needs a notice

The Act covers three kinds of work. Most London loft conversions, rear extensions and basements in terraced and semi-detached houses fall under at least one of them.

Minor work may need no notice. The government's booklet puts the test as whether the work might affect the structural strength and support functions of the party wall as a whole.

What a notice must say

There is no official form. The notice must give your name and address, the address of the building to be worked on, a full description of the work and the date you plan to start, and it should be dated. An excavation notice must also say whether you plan to strengthen or safeguard the neighbour's foundations, and plans and sections showing the excavation must go with it. A notice is valid for one year, so serving it long before the build gains nothing. The neighbour can agree in writing to an earlier start but does not have to.

What happens after you serve it

For work on a party wall (section 2) and for excavations (section 6):

• The neighbour consents in writing. Nothing is in dispute and there is no requirement to appoint a surveyor. A dispute can still arise later, for example over damage.
• The neighbour refuses, or does nothing for 14 days. A dispute is treated as having arisen, and the surveyor procedure below applies.

After a notice for party wall work (section 2), the neighbour can also serve a counter notice asking for additional work. It must be given within one month, and you must respond within 14 days or a dispute is treated as having arisen.

For a new wall on the boundary (section 1) the outcome depends on where the wall stands:

• Astride the boundary. If the neighbour consents within 14 days, the wall can go ahead as agreed and the cost is shared in proportion to use. If they do not consent in writing within 14 days, you must build the wall wholly on your own land and at your own expense.
• Wholly on your land, up to the boundary. Unless the neighbour objects, you can start one month after serving the notice. Foundations may project under the neighbour's land only where necessary, and special foundations, as the Act defines them, need their written consent.
• If the owners disagree about either kind of wall, the surveyor procedure applies, but surveyors cannot decide where the boundary lies.

Surveyors and the party wall award

When there is a dispute, the two owners either agree on one surveyor, called the Agreed Surveyor, or each appoints a surveyor and the two work together. A third surveyor is selected to decide any point on which the two cannot agree. The surveyors produce an award, a legal document that sets out the work to be done and how it is to be done. Each owner has 14 days from receiving the award to appeal against it to the county court.

The owner who starts the work normally pays the costs of drawing up the award. The neighbour can be asked to share costs where the work is needed because of a defect or need for repair in the wall.

Rights and duties while the work is on

• The neighbour must let your workers and surveyor in when it is necessary for work carried out under the Act, and only for that work, after 14 days notice except in an emergency. Obstructing access is an offence that can be prosecuted in the magistrates' court.
• You must make good any damage the work causes, and the neighbour is entitled to compensation for loss or damage.
• The neighbour can ask for security for expenses before work starts. This is usually kept for particularly intrusive or complex work, such as basements.

Party walls, planning and building regulations

The Act is separate from planning and from building regulations. A party wall award does not remove the need for planning permission or building regulations approval, and having those approvals does not remove the duties under the Act. For the other two, see our guides to permitted development and lawful development certificates and to building regulations sign-off. In a conservation area, read what needs planning permission in a conservation area as well.

Questions to answer before you set a start date

• Is the wall shared with the neighbour, and will any beam bear into it? This is the usual case for a loft conversion in a terrace.
• Will a new wall of the extension stand on or astride the boundary?
• How close to the neighbour's building, and how deep, will the foundations or a basement be?
• Is a chimney breast on the party wall coming out?
• Does the programme leave at least two months for notices on party wall work, and one month for boundary walls and excavations?

Frequently asked questions

Do I need a party wall agreement for a loft conversion?

Usually you need to give notice. Cutting into a party wall to take the bearing of a beam is work under section 2 of the Party Wall etc. Act 1996, which needs at least two months written notice to the neighbour. An award, the document most people call a party wall agreement, is only needed if the neighbour does not consent in writing.

Do I need a party wall agreement for a rear extension?

It depends on the wall and the foundations. A new wall built up to or astride the boundary needs one month's notice under section 1. Foundations dug within 3 metres of a neighbour's building and deeper than its foundations, or within 6 metres where they meet a line drawn down at 45 degrees from them, need one month's notice under section 6. An extension built clear of the boundary on shallow foundations may need no notice.

Do I need to give party wall notice to remove a chimney breast?

Yes. The government's explanatory booklet lists cutting off projections from a party wall, with removing a chimney breast as the example, among the section 2 works that need at least two months notice.

What happens if my neighbour does not reply to a party wall notice?

For work on a party wall or an excavation, if the neighbour does nothing within 14 days a dispute is treated as having arisen. The two owners then agree on one surveyor or appoint one each, and the surveyors draw up an award that sets out the work and how it is to be done. A new boundary wall is different: without written consent within 14 days a wall astride the boundary must be built wholly on your own land, and a wall wholly on your land can start one month after the notice unless the neighbour objects.

How long is a party wall notice valid?

One year. A notice stops being valid if the work has not started within a year, so serve it with the planned start date in mind.

Does planning permission cover party wall matters?

No. The Party Wall etc. Act 1996 is separate from planning permission and building regulations. Approval under one does not remove the need to follow the others.

Sources

• The Party Wall etc. Act 1996: explanatory booklet, Ministry of Housing, Communities and Local Government
• Party Wall etc. Act 1996, legislation.gov.uk

This guide summarises the Party Wall etc. Act 1996 from the government's explanatory booklet. It is general information, not legal advice. If a dispute arises, the surveyors appointed under the Act decide it.