Published 4 September 2026 | By FJP Investment Editorial Team

A neighbour announcing plans for an extension can quickly raise questions about exactly where they are entitled to build.

Can they build right up to the fence? Can their new wall sit on the boundary itself? Can foundations extend underneath your garden? And what happens if you believe the proposed extension actually crosses onto your land?

The short answer is that a neighbour can sometimes build right up to a property boundary, but that does not mean they can simply build wherever they like.

Several different areas of law and regulation can become relevant, including:

• ownership of the land;
• the precise position of the boundary;
• the Party Wall etc. Act 1996;
• planning permission or permitted development;
• building regulations;
• rights of access;
• easements and restrictive covenants; and
• potential rights to light.

These issues are related, but they are not the same thing.

This guide explains what homeowners in England and Wales should understand when a neighbour wants to build close to, up to or across a shared boundary.

Important: This article provides general information rather than legal, planning or surveying advice. Boundary disputes can turn on historic deeds, physical evidence and individual circumstances. The Party Wall etc. Act 1996 applies in England and Wales; different rules apply in Scotland and Northern Ireland.

Can a neighbour build right up to the boundary?

Potentially, yes.

There is no universal rule requiring every house extension or new wall to leave a particular gap between the building and the legal boundary.

A neighbour may therefore be able to construct a wall wholly on their own land but immediately alongside the boundary, provided that the development complies with the relevant planning, building-control and private-law requirements.

However, where the proposed work falls within the Party Wall etc. Act 1996, the neighbour may have to serve formal notice before work begins.

For a new wall being built wholly on one owner’s land but up against the boundary line, government Party Wall guidance says the adjoining owner should normally receive at least one month’s notice.

The government’s detailed Party Wall etc. Act explanatory booklet sets out the procedure.

Can a neighbour build a wall directly on the boundary line?

This requires an important distinction.

A wall can be:

• wholly on one owner’s land but immediately alongside the boundary; or
• astride the boundary, meaning the wall itself sits partly on each property.

Those are not the same thing.

Under section 1 of the Party Wall etc. Act, a person proposing to build a new wall astride the boundary must serve a Line of Junction Notice.

More importantly, they do not have an automatic right to build the new wall partly on their neighbour’s land.

The adjoining owner must consent to that arrangement in writing.

If consent is not given, government guidance says the new wall must instead be built entirely on the building owner’s own land.

So if somebody proposes a new extension wall that actually straddles the legal boundary, the answer is not simply:

“It’s my extension, so I can put the wall there.”

Ownership of the land still matters.

What exactly is the boundary?

This can be considerably less obvious than homeowners expect.

A fence, hedge or garden wall may appear to show the dividing line, but the physical feature on the ground is not necessarily the exact legal boundary.

Likewise, homeowners sometimes obtain their title plan from HM Land Registry and assume that the red line identifies the boundary to the centimetre.

Usually, it does not.

HM Land Registry operates what is known as the general boundaries rule.

Most title plans show the general extent of the registered land rather than the precise legal position of every boundary.

HM Land Registry’s Practice Guide 40 explains that title plans and boundaries need to be considered together with the register and relevant deeds. :contentReference[oaicite:1]{index=1}

Our Homeowner’s Guide to HM Land Registry explains the title register and title plan in more detail.

Does the fence always belong to the property on one side?

No.

There is a surprisingly persistent belief that a homeowner automatically owns the fence on a particular side of their garden.

There is no reliable universal left-hand or right-hand rule.

Responsibility may be established by:

• the title register;
• historic conveyances or transfers;
• deed plans;
• boundary agreements;
• physical evidence; or
• the history of how the properties have been occupied.

Some deeds contain inward-facing T marks indicating responsibility for a particular boundary feature, but not every property has them and their significance needs to be read in context.

Where the exact boundary affects a proposed extension, guessing based on who has historically painted or replaced the fence is not a sensible substitute for checking the title documentation.

What is a Line of Junction Notice?

The Party Wall etc. Act uses the term line of junction to describe the boundary between adjoining properties.

If a neighbour intends to construct a new wall on or immediately alongside that boundary, section 1 of the Act can require them to notify the adjoining owner.

The notice should describe the proposed work and normally be served at least one month before construction starts.

If the proposal is to build a new party wall astride the boundary, the adjoining owner’s written consent is needed.

If that consent is not given, the wall generally has to be constructed wholly on the building owner’s land.

What if the new wall is entirely on the neighbour’s side?

A neighbour does not ordinarily need you to transfer part of your land simply because they want to construct close to it.

If their wall is genuinely built entirely inside their legal boundary, they may be able to build right up against the line.

But that still does not mean every other legal requirement disappears.

The project may require:

• a Party Wall notice;
• planning permission;
• building-regulations approval;
• compliance with restrictive covenants; or
• consideration of neighbouring rights.

The development also cannot simply encroach onto land belonging to somebody else.

Can foundations extend underneath a neighbour’s land?

This is another area where the Party Wall Act becomes particularly relevant.

Ordinary foundations may sometimes project beyond the face of a wall and underneath neighbouring land where that is necessary for the construction covered by the Act.

However, the legislation distinguishes ordinary foundations from what it calls special foundations, which include certain reinforced foundations.

Special foundations cannot be placed under neighbouring land without the adjoining owner’s written consent.

If you receive Party Wall drawings showing foundations extending beyond the apparent boundary, do not assume either that they are automatically unlawful or that the builder can put whatever they like beneath your property.

The proposed foundation design and the relevant Party Wall rights should be properly understood.

What if the extension is excavated close to your house?

The Party Wall Act is not limited to shared walls.

It can also apply where somebody excavates for foundations close to a neighbouring building.

Broadly, notices can be required where excavation is:

• within three metres of a neighbouring building and goes below the bottom of its foundations; or
• in certain circumstances, within six metres where the proposed excavation intersects a 45-degree line measured from the neighbouring foundations.

Plans and sections showing the proposed excavation need to accompany the relevant notice.

The reason is obvious: excavation beside an existing property can potentially affect the support provided by the surrounding ground.

Does planning permission mean the neighbour can build on your land?

No.

This is a very important distinction.

Planning permission deals with whether a development is acceptable from a planning perspective. It does not transfer ownership of somebody else’s land.

A local authority could therefore grant planning permission for a design without resolving a private dispute about the exact boundary, an easement or another private property right.

Likewise, Party Wall compliance does not replace planning permission.

The government’s Party Wall guidance expressly states that the Act is separate from planning permission and building-regulation approval. :contentReference[oaicite:2]{index=2}

A homeowner may therefore need to deal with several different processes at the same time.

Can you object to your neighbour’s planning application?

Yes, where a planning application is required you can normally make representations to the local planning authority.

Relevant planning considerations may include matters such as:

• overlooking and privacy;
• the scale and design of the development;
• loss of outlook;
• effects on the character of the area;
• parking or highway implications; and
• certain effects on neighbouring amenity.

But a planning objection is not the mechanism for deciding who legally owns a disputed strip of land.

Boundary ownership is primarily a private property matter.

Does permitted development remove Party Wall requirements?

No.

Some household extensions may be carried out under permitted development rights rather than requiring a conventional planning application.

That does not mean the Party Wall etc. Act stops applying.

The two systems answer different questions.

A development can therefore be permitted from a planning perspective while still requiring a Party Wall notice.

Likewise, serving a perfectly valid Party Wall notice does not establish that the extension complies with planning rules.

Can a neighbour attach their extension to your wall?

Potentially, depending on the ownership and status of the wall and the work proposed.

If the structure is an existing party wall or party structure, section 2 of the Party Wall Act provides rights for certain types of work but also imposes procedures intended to protect the adjoining owner.

Work affecting an existing party wall generally requires at least two months’ notice.

The Act can cover matters including cutting into a party wall, increasing its height, repairing it and carrying out certain structural works.

This is different from simply deciding to attach a new structure to a wall that belongs entirely to somebody else.

Where ownership is unclear, professional advice should be obtained before construction starts.

Do you have to agree to a Party Wall notice?

No.

Receiving a Party Wall notice does not mean you have to sign consent immediately.

For many types of Party Wall work, an adjoining owner can:

• consent to the proposed works;
• disagree with them; or
• take no action, in which case a dispute may be deemed to have arisen after the statutory period.

Where a dispute arises, surveyors can be appointed under the Act and a Party Wall Award can set out how the work is to proceed.

However, a surveyor is not automatically required simply because a Party Wall notice exists.

If the neighbour understands the work and is happy to consent, the Act does not require both sides to appoint surveyors unnecessarily.

What does a Party Wall surveyor actually decide?

A Party Wall surveyor deals with matters falling within the Party Wall etc. Act.

Their role is not normally to determine every possible disagreement between two neighbours.

A Party Wall Award may address matters such as:

• the work that can be carried out;
• how it will be undertaken;
• working hours or practical safeguards;
• access where relevant;
• protection of the adjoining property;
• a schedule of condition; and
• responsibility for damage caused by the works.

A genuine dispute over legal ownership of land may require separate boundary advice rather than simply referring everything to the Party Wall surveyor.

What if your neighbour builds over the boundary?

If a building physically crosses the legal boundary onto land belonging to somebody else without an appropriate legal right or agreement, this can potentially amount to trespass.

That should be dealt with quickly.

The sensible first step is usually to establish the facts rather than immediately assuming deliberate encroachment.

Check:

• the title register and title plan;
• historic deeds;
• approved plans;
• Party Wall documents;
• the actual position of the construction; and
• whether a surveyor has accurately established the boundary.

If there genuinely appears to be an encroachment, take specialist legal and surveying advice.

Potential remedies depend heavily on the circumstances. A court will not necessarily order the same solution in every boundary case.

Do not rely on the thickness of a line on the Land Registry plan

This deserves repeating because it causes so much confusion.

Land Registry title plans usually show general boundaries.

A red line shown on a plan at normal Land Registry scale can represent a much wider area on the ground than the few centimetres being argued about.

HM Land Registry itself explains that the title plan identifies the general extent of the registered title; it usually does not establish the exact boundary line. :contentReference[oaicite:3]{index=3}

If the disagreement concerns whether an extension is 50mm or 150mm over the legal boundary, simply enlarging a Land Registry PDF is unlikely to provide the answer.

Can an exact boundary be formally recorded?

Potentially.

Neighbours can sometimes enter into a boundary agreement recording the agreed position of a boundary.

There is also an HM Land Registry procedure for applying for a determined boundary, which records the precise line to a much greater degree of accuracy than the general-boundary system.

These procedures are different and the appropriate approach depends on whether the neighbours agree.

Professional legal and surveying assistance is normally sensible where the precise position is important.

What about access to your garden to build the extension?

Building next to a boundary can create a practical problem: the neighbour’s contractor may want to stand on your land, erect scaffolding or temporarily access your garden.

The fact that somebody has planning permission does not by itself give their builders an unrestricted right to enter your property.

However, specific legal access rights can exist.

For example, the Party Wall Act includes access provisions for certain work properly carried out under that legislation.

Separate legislation can also potentially allow court-authorised access to neighbouring land where access is reasonably necessary to carry out certain preservation works.

Our recently updated guide to right of access to property, neighbours and repairs explains those rules in considerably more detail.

What about easements and restrictive covenants?

A planning consent and a Party Wall process do not necessarily remove private rights contained in the title.

A property can be affected by:

• rights of way;
• rights of support;
• rights of drainage;
• rights to use particular land;
• restrictive covenants controlling development; or
• other easements benefiting neighbouring property.

The Party Wall Act itself does not simply extinguish those other property rights.

Our guide What Is an Easement? explains how these rights can affect neighbouring land.

Can building close to the boundary affect property value?

Potentially.

A poorly positioned development might affect:

• privacy;
• outlook;
• natural light;
• garden character;
• future extension potential; or
• the overall appeal of the property.

But there is no automatic formula saying that a neighbour building on or close to a boundary reduces a property’s value by a particular percentage.

In many suburban streets, extensions close to boundaries are commonplace and have little negative effect where they are well designed.

The individual development and local market matter.

What should you do if your neighbour tells you they are extending?

Keeping the discussion practical from the outset can prevent a relatively ordinary building project turning into an expensive dispute.

1. Ask to see the plans

Understand what is actually proposed rather than relying on a conversation over the fence.

2. Establish where the boundary is believed to be

Review the title documentation and historic plans where necessary.

3. Ask whether the Party Wall Act applies

The answer will depend on the type and location of the work.

4. Check the planning position

If there is a planning application, review the actual drawings through the local council’s planning portal.

5. Raise concerns before work starts

Moving a proposed wall by a small distance on a drawing may be straightforward. Resolving the same issue after foundations have been poured is much harder.

6. Use professional advice where the boundary genuinely matters

A boundary surveyor, Party Wall surveyor or property solicitor may be appropriate depending on the issue.

What if you are the person planning the extension?

The same principle applies in reverse.

Do the groundwork early.

Before committing to a design that uses every available centimetre beside a neighbouring property:

• check your title;
• understand the boundary;
• establish whether planning permission is required;
• check whether the Party Wall Act applies;
• consider how the builders will access the site;
• review foundations and drainage;
• check easements and restrictive covenants; and
• talk to the neighbour before formal notices arrive unexpectedly.

If extra land is genuinely required, buying a small strip from the adjoining owner may occasionally provide a cleaner solution than designing around a disputed boundary.

Our guide to buying land from a neighbour explains the issues involved.

Frequently asked questions

Can my neighbour build right up to my boundary?

Potentially. A wall can sometimes be constructed wholly on the neighbour’s own land but immediately alongside the boundary. Planning, building regulations, Party Wall requirements and private property rights still need to be considered.

Can my neighbour build actually on the boundary?

A new wall built astride the boundary requires the adjoining owner’s written consent under the Party Wall etc. Act. Without that consent, the building owner generally has to construct the wall wholly on their own land.

How much notice must my neighbour give before building on the boundary?

For a new wall at the line of junction under section 1 of the Party Wall Act, the statutory notice period is normally at least one month. Work affecting an existing party wall generally requires at least two months’ notice.

Can I refuse permission for my neighbour to build beside the boundary?

You cannot necessarily prevent lawful construction simply because it is close to your boundary. However, you do not have to consent to a new party wall being built astride the boundary on your land. You may also have rights under planning, Party Wall or private property law depending on the circumstances.

Can foundations go under my garden?

Certain projecting foundations may be permitted under the Party Wall Act where necessary, but special foundations cannot be placed under neighbouring land without written consent. Specialist advice may be appropriate where foundations cross the boundary underground.

Does planning permission override my boundary?

No. Planning permission does not transfer ownership of your land or eliminate private property rights. Planning and land ownership are separate matters.

Is the red line on a Land Registry plan the exact boundary?

Usually not. Most Land Registry title plans use the general-boundaries system and show the general position rather than the exact legal line.

Can I stop builders coming into my garden?

Builders do not automatically have unrestricted access merely because the neighbour is carrying out work. However, statutory rights of access can arise in certain situations, including some works under the Party Wall Act.

What if my neighbour has already built over the boundary?

Establish the legal boundary and extent of any encroachment first. If the structure genuinely crosses onto your land without an appropriate right, obtain specialist property-law and surveying advice promptly.

Final thoughts

When somebody asks whether a neighbour can build on the boundary, the answer depends heavily on what “on the boundary” actually means.

Building a wall entirely on one’s own property but immediately beside the boundary can be lawful.

Building a new wall partly on somebody else’s land is a different matter.

The Party Wall etc. Act provides a framework for dealing with many forms of boundary construction, party-wall work and nearby excavation, but it does not replace planning law and it does not make questions of land ownership disappear.

The first thing to establish is therefore the simplest:

Where is the legal boundary, and where is the proposed building in relation to it?

Jamie Johnson, CEO of FJP Investment, comments: “Boundary problems are a good example of something that can be very easy to deal with before the work starts and extremely difficult afterwards. If two neighbours understand where the boundary is and what is actually being built, most of the uncertainty disappears. It’s when assumptions are made and concrete starts being poured that relatively small disagreements can become expensive ones.”

For homeowners planning building work, discussing the proposal early and following the correct Party Wall, planning and legal procedures can save a considerable amount of unnecessary conflict.

For the adjoining owner, the objective should be the same: understand the plans, establish your rights and deal with genuine concerns before construction progresses.

This article is provided for general information only and should not be regarded as legal, planning, surveying or property advice. Boundary and Party Wall issues depend on the individual circumstances and documentation. Appropriate professional advice should be obtained where required.