Single Storey Extension Party Wall Guide (London + England and Wales)

Table of Contents

Quick answer

A party wall notice for a single storey extension is usually needed if you build on or near the boundary, or if you dig foundations close enough that your trench could go deeper than your neighbour’s foundations. Serve the right notice early. If your neighbour disagrees or stays silent, surveyors can agree a Party Wall Award so the work can move forward.

Who this guide is for

This guide is for homeowners planning a ground floor extension in England and Wales. The Party Wall etc. Act 1996 applies there. Most examples use London-style housing (terraced and semi-detached) because party wall issues are common there. Scotland and Northern Ireland use different rules, so check local guidance if your property is outside England and Wales.

If you are building in London

London homes are close together, so extensions often touch shared walls or involve digging near next door.

Costs in London:

Section 6 excavation notices service:

Why party wall rules show up in ground floor extensions

Most homeowners hear about the Party Wall Act after they have booked a builder. That is the wrong time. A ground floor extension often needs new foundations, drainage runs, or a wall close to the boundary. Those are the exact situations where the Act can apply.

The point is simple: the law gives you a process to follow, and it gives your neighbour a way to protect their home. If you plan it early, it usually stays calm. If you leave it late, it can pause the whole build.

The 3 triggers that matter for a single storey extension

A single storey extension party wall issue normally comes from one or more of these triggers.

1) Building up to the boundary (line of junction)

If your new extension wall sits on the boundary line, or right up against it, you may need notice. This is common for side extensions and side return extensions.

If you want the new wall to sit astride the boundary and become a shared wall, your neighbour must agree in writing. If they do not agree, you usually keep the wall on your land.

2) Excavating near your neighbour’s foundations (the 3m and 6m rules)

This is the most common trigger for a ground floor extension. Foundations mean digging. If you dig close enough and deep enough, you need to notify your neighbour under the Act.

3) Work to an existing shared wall (party structure)

Some extensions need steel beams or support details that touch a shared wall, such as cutting pockets into the party wall for beams. That can also trigger notice.

Checklist: do you need a party wall notice for your extension?

Use this checklist before you lock your start date. Tick any that apply:

Your new wall will sit on the boundary line or right next to it.
You want to build a wall astride the boundary (a shared wall).
You will dig for foundations, ground beams, or drainage trenches.
Your excavation will be within 3 metres of your neighbour’s building (house, rear addition, garage, conservatory).
Your excavation could be deeper than the bottom of your neighbour’s foundations.
You need to cut into, underpin, or otherwise work on a shared wall.

If you tick one or more, plan for party wall steps early. If you are unsure, ask a party wall surveyor to confirm before you start.

If you want a professional check before you serve notice, see: Building Owner Survey service.

Fast decision tool: which notice do you need?

Use this as a quick guide. Your surveyor can confirm the correct notice type based on your drawings.

Online notice decision tree and cost estimator:

Building a new wall on or up to the boundary line: usually a Section 1 notice.
Cutting into, raising, or otherwise working on a shared wall: usually a Section 2 notice.
Digging for foundations close to next door (3m/6m rules): usually a Section 6 notice.

The 3m and 6m excavation rules in plain English

People call it the 3 metre rule, but there is also a 6 metre rule. The idea is about distance and depth. If you excavate close to your neighbour’s building and your excavation goes deeper than their foundations, you may need a Section 6 notice.

You do not need to guess. Use your designer’s foundation details and let a surveyor check whether your foundation depth and distance triggers the rule.

Two quick tips that save trouble:

Include nearby structures. A neighbour’s rear extension, conservatory, or outbuilding can count as a building for these rules.
Watch for changes. If your engineer changes your foundation design later, re-check the party wall position before work starts.
Do not forget drainage. Deep drainage trenches close to next door can matter in the same way as foundations.

Notice types and minimum timeframes

Most single storey and ground floor extensions use one or two notice types. The minimum notice period depends on the section of the Act.

Work type	Common extension example	Typical notice	Minimum notice period
Wall on or up to the boundary	Side wall built right to the boundary	Section 1 (line of junction)	1 month
Work to a shared wall	Beam pocket cut into a party wall	Section 2 (party structure)	2 months
Excavation near neighbour	Foundations within 3m/6m zone	Section 6 (adjacent excavation)	1 month

A project can need more than one notice. For example, you might be building up to the boundary and also digging close to next door.

Step-by-step: how to serve notice without causing delays

Step 1: speak to your neighbour early

A short friendly chat usually does more than a perfect letter. Show a simple plan, explain roughly when the noisy work will happen, and be open to questions. Neighbours are far more likely to consent when they do not feel surprised.

Step 2: identify the right people to serve

You must serve the adjoining owner. That can be more than one person. In flats, it can include freeholders and long leaseholders. If you get the name wrong, you can lose time and have to serve notice again.

Step 3: include the details your neighbour actually cares about

For a ground floor extension, most worries are about digging and damage. Include:

a site plan showing the boundary
the extension plan
a section showing foundation depth and distance to the neighbour’s building
your planned start date (even if it might move)

If your foundation depth is not final yet, do not guess. Ask your engineer for a best current estimate and state that it may change.

Step 4: use clear wording (copy and paste starter)

Keep the notice simple: who you are, what work you plan, and the earliest start date. Copy-and-paste templates (PDF and Word):

Step 5: deliver it in a way you can prove

Send it in a way you can track, or hand deliver and keep a note of the date. Many people use a surveyor to serve notices because a small mistake can waste weeks.

What happens after you serve notice

Your neighbour normally has 14 days to reply. They can consent, dissent, or ignore the notice.

If they consent

Consent means you can usually move on after the notice period ends, as long as you stick to what you described. Even with consent, a Schedule of Condition is smart. It records the condition of the neighbour’s property before work starts.

Schedule of Condition guide:

Schedule of Condition service:

If they dissent

Dissent is not personal. It often just means they want the formal protections of a Party Wall Award. At that point, surveyors are appointed and the process moves forward.

If they ignore the notice

Silence is common. Do not keep waiting and hoping. Follow the formal next steps so the process can move forward. This is where most extension delays happen.

Guide: Neighbour ignoring party wall notice

Can your neighbour send a counter notice?

In some cases, an adjoining owner can serve a counter notice asking for changes or extra work that benefits them, as long as it fits within the rules of the Act. If this happens, surveyors usually help agree what is reasonable.

Counter notice guide: https://www.surveyofpartywall.co.uk/counter-notice-party-wall-act/

Access and working near the boundary

Some single storey extensions are tight to the boundary. You might need access onto your neighbour’s land to do parts of the work safely, such as putting up protection, repairing a boundary fence, or finishing a wall face.

If you need access, do not rely on a casual promise. Put it in writing and agree dates and times. If the job is in dispute and there is an Award, access and protection measures are usually written into it.

Tip: Access requests go down better when you explain what you will protect (plants, paving, sheds) and when you will remove any temporary items.

What surveyors do (and what the Party Wall Award usually includes)

Surveyors set rules for the work and reduce disputes. They do not work for your neighbour or for you. They are meant to be fair under the Act.

A Party Wall Award often covers:

what work is allowed, linked to the drawings
how the work must be done (methods and protections)
working hours and access arrangements
a Schedule of Condition
how damage will be dealt with and repaired
who pays surveyor fees and when

If you want surveyors to manage the dispute route and produce the Award, see: Party Wall Agreements and Awards service (https://www.surveyofpartywall.co.uk/services/party-wall-agreements-awards-london/).

Simple explainer: Party wall survey and what surveyors do

Damage: What happens if cracks appear?

This is the worry behind most disputes. A Schedule of Condition gives a clear before record. After the work, if a crack appears, the surveyor route normally focuses on two questions: was it already there, and was it caused by the works?

A good Award usually sets a clear method for dealing with damage, such as inspection, making good, or compensation if repair is not practical.

Schedule of Condition guide:

A realistic timeline for a ground floor extension

The timeline depends on neighbour response and complexity, but you can plan around a sensible range. The big mistake is treating party wall as paperwork you can do in a few days.

Stage	What you do	Why it matters
Early design	Speak to neighbour, share a sketch	No surprises
Drawings ready	Confirm which notice applies	Right notice, fewer errors
Serve notice	Serve at least 1-2 months before start	Notice periods apply
Wait for reply	Track the 14-day response window	No reply can trigger surveyors
If consent	Record condition (SoC)	Protects both sides
If dissent/no reply	Surveyors agree an Award	Sets rules for the work
Start build	Follow the Award and keep updates short	Less friction, fewer claims

Full timeline and what happens at each stage:

Extension-specific guide: Do I need a party wall agreement?

Costs: what to budget for

Costs vary by project, neighbour response, and how many surveyors are involved. Budget early so you are not forced into risky shortcuts.

London note: fees and timelines can increase when you have more than one affected neighbour, tight access, or complex foundations. For a London-focused breakdown, read:

Notice preparation and service costs

Some owners do this themselves. Others pay for a notice service to avoid errors. Guide:

Surveyor fees

Fees depend on complexity and whether you use one agreed surveyor or two surveyors. Guide:

Who pays?

In many extension cases, the building owner pays because it is their project. But there are exceptions and cost-sharing situations. Guide:

How to keep costs under control

These moves often reduce cost and delay:

Serve notices early, with clear drawings, so you avoid re-serving.
Offer a Schedule of Condition even if your neighbour consents.
Keep your scope stable. Last-minute design changes create extra surveyor time.
Use one agreed surveyor when relations are good and the project is simple.

Common mistakes that delay single storey extensions

Booking a builder start date before notice is served

If your builder is ready in four weeks but you need a two-month notice, the plan will not match reality. Serve notices as soon as your drawings are stable.

Mixing up planning permission and party wall rules

Planning permission is about the council. Building control is about safety. Party wall duties are about neighbours and shared risks. You can have planning approval and still need to serve notice.

Vague notices and missing drawings

Most neighbour worries are about foundation depth and distance. If you skip that detail, you invite questions and delays.

No Schedule of Condition

Without a before record, small pre-existing cracks can turn into big arguments after the work starts.

Ignoring the 14-day and follow-up steps

If your neighbour does not reply, follow the correct next steps so the process moves forward. Guide: /neighbour-ignoring-party-wall-notice/

How to keep the neighbour relationship steady

These small habits reduce tension during a ground floor extension:

Share dates for noisy work.
Keep the site tidy near the boundary.
Give a weekly update by message.
Tell them about any change before they find out from the builder.

If you are on the receiving end of a notice, this page includes reply templates: /how-to-respond-party-wall-notice/

FAQs

Do I need a party wall notice for a rear single storey extension?

Often yes, because the foundations can fall within the excavation rules. If your dig is close and deep, get it checked early.

How much notice do I need to give?

It depends on the type of notice. Section 2 work to a shared wall has a longer minimum notice period than Section 1 and Section 6. Use the notice table above as your planning guide.

What if my neighbour says no?

They can dissent. That does not always stop the project. It usually means surveyors will set rules through a Party Wall Award so the work can proceed safely.

What if my neighbour ignores my notice?

Do not leave it sitting there. Follow the correct next steps so the process can move forward. Guide:

Can my neighbour ask for extra work through a counter notice?

Sometimes, yes. A counter notice can request changes that protect their property or ask for certain works. Surveyors usually help decide what is reasonable.
Counter Notice

Who pays the surveyor?

In many cases the building owner pays, but there are details and exceptions. Guide: /who-pays-for-party-wall-surveyor-complete-payment-guide-2026/

Should I get a Schedule of Condition even if my neighbour consents?

Yes, in most cases. It protects both sides by recording the before condition.

Next steps

If you are planning a single storey extension, do these three things in order:

Check whether Section 1, 2, or 6 applies using the decision tool above.
Speak to your neighbour and show the drawings.
Serve the right notice early enough to protect your build start date.

Process overview (/party-wall-process-step-by-step-from-notice-to-award/)

Need help with a London ground floor extension?

If you want the process handled end-to-end, these pages match the most common extension needs:

Talk to our London team: Contact us

Legal note

This guide is general information for England and Wales. It is not legal advice. Party wall duties depend on your drawings and your site. If you are unsure, speak to a qualified party wall surveyor before starting work.

Single Storey Extension Party Wall Guide London + England and Wales