If you are extending or converting the loft of a terraced or semi-detached home in London, you will almost certainly need a party wall agreement. It sounds daunting, but it is a routine, well-established process. This guide explains what the Party Wall etc. Act 1996 covers, how the process works, and what it costs.
What is the Party Wall etc. Act 1996?
The Party Wall etc. Act 1996 is the law that governs work affecting a wall or structure shared with a neighbour, and excavation close to their property. Its purpose is to protect both sides: it gives the adjoining owner rights over work that could affect their property, and it gives you a clear legal route to carry out the work.
When does it apply?
The Act is usually triggered by:
- Work on a party wall or party structure — for example, inserting steel beams for a loft conversion or extension into a shared wall.
- Building a new wall at or on the boundary between two properties.
- Excavation within 3 metres of a neighbouring structure (or 6 metres for deeper excavations), which is common when digging foundations for an extension.
In practice, most London loft conversions and extensions on terraced or semi-detached houses fall within the Act.
How the process works
Serve notice
You serve written notice on the adjoining owner. The notice period is two months for building works and one month for excavation.
Neighbour responds
They can consent in writing, or dissent. If they consent in writing, no surveyor is needed and there is no fee.
Surveyors appointed
If they dissent, or do not respond in time, a party wall surveyor is appointed. Each side can appoint their own, or they can agree on one surveyor for both.
The award
The surveyor produces a party wall award, which records the work, the condition of the neighbouring property, and any measures required to protect it.
What it costs
If your neighbour consents in writing, there is no cost. If surveyors are involved, the building owner (the person doing the work) normally pays both sides’ reasonable surveyor fees. As an indicative guide, budget around £700 to £2,500 per affected neighbour. We factor this into your project plan so there are no surprises.
Does it hold up the build?
It can, if notices are left late. The notice periods are the reason we raise party wall matters at the very start of a project, so notices can run in parallel with design and building control and do not delay the build.
How we help
LET-HD Developments handles party wall matters as part of the project, serving notices and liaising with surveyors. You can read more about our loft conversion service and our house extension service.
Frequently asked questions
Can my neighbour refuse and stop the work?
No. A neighbour cannot refuse the work under the Act. If they dissent, the process simply moves to a surveyor and an award. The work can still proceed lawfully.
Do I need a party wall agreement for a detached house?
Usually not, unless you are excavating close to a neighbouring structure. It most often applies to terraced and semi-detached homes.
Who pays for the surveyor?
The building owner normally pays the reasonable fees of both parties’ surveyors. Written consent within the notice period avoids the cost entirely.
Building in London? Talk to us first
Call +44 (0) 203 355 5313 or use our contact form and we will explain what your project needs, free of charge.