What Is a Party Wall Agreement and When Do You Need One?

A Clear Guide for Homeowners Planning Extensions, Lofts, and Renovations in London

If you're planning to build near or on a shared wall — such as with a house extension, loft conversion, or basement renovation — you may have heard the term Party Wall Agreement.

But what exactly is it? When is it required? And what happens if you don’t have one?

In this article, we explain everything London homeowners need to know about Party Wall Agreements — in plain English.

🧾 What Is a Party Wall?

A party wall is a wall that you share with your neighbour, typically between:

• Terraced or semi-detached houses

• Flats and maisonettes

• Garden walls built along the boundary line

A Party Wall can also be:

• A wall or structure on the boundary line between two properties

• A floor or ceiling separating flats

• A shared chimney stack or supporting beam

  
  

What Is a Party Wall Agreement?

A Party Wall Agreement (also called a Party Wall Award) is a legal document drawn up under the Party Wall etc. Act 1996.

It outlines:

• What building work is taking place

• How it may affect the neighbouring property

• When the work will be done

• Any protections in place (e.g. vibration monitoring, crack surveys)

It’s designed to protect both parties — preventing disputes and damage claims by agreeing on the scope and method of work ahead of time.

When Do You Need a Party Wall Agreement?

You’ll need to serve a Party Wall Notice (and potentially obtain an Agreement) if your work includes:

Common examples:

• Building a rear or side extension that involves foundations near the boundary

• Converting a loft that requires inserting steel beams into a party wall

• Removing a chimney breast

• Excavating within 3 metres (or 6m in some cases) of a neighbour’s wall or foundations

• Raising a party wall or cutting into it for structural support

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🕒 When Should You Serve Notice?

You must give your neighbours at least 1–2 months’ notice before work starts:

Type of Work	Notice Period
Line of junction (new wall at boundary)	1 month
Party wall or structure work	2 months
Excavations near a neighbour’s foundation	1 month

What Happens After You Serve Notice?

Your neighbour can:

1. Consent – You can go ahead (in writing)

2. Dissent and appoint a Party Wall Surveyor – You’ll both need a surveyor (or share one) to draft an official Party Wall Award

3. Ignore the notice – After 14 days, it’s treated as a dissent and a surveyor must be appointed

If surveyors are involved, costs typically fall to the person doing the building work.

How Much Does a Party Wall Agreement Cost?

• Simple consent (no surveyor): Free or £50–£200 for paperwork

• Shared surveyor: £800–£1,200

• Separate surveyors: £1,500–£2,500+ (per party)

At Morphos Group Ltd, we can help serve the notice, coordinate with surveyors, and manage the full process as part of your project.

What Happens If You Don’t Get a Party Wall Agreement?

• Your neighbour can take legal action to stop the work

• You may be liable for property damage, even if caused accidentally

• Your build may be delayed or declared unlawful

• It could complicate a future sale of your property

  
  

Final Thoughts

Party Wall Agreements can seem complicated, but they’re a critical legal step when working on or near a shared boundary. Getting it right protects you, your project, and your relationship with your neighbours.

Planning an Extension or Loft Conversion?

Let Morphos Group Ltd manage the process — from drawings and notices to full construction. We handle Party Wall matters as part of our design & build services across London.

Book a free consultation and get expert advice on whether your project needs a Party Wall Agreement.