An extension is a significant investment in your home. If the plans bring a new wall or foundations close to your neighbour's property, uncertainty about the boundary can become a legal dispute. Its position affects where you may build, whether the work might encroach on neighbouring land and what access you may need.
If a neighbour challenges the boundary after work begins, resolving it could mean design changes, delays or formal action. Lamb Brooks' property disputes team advises on boundary, encroachment and access disputes. Understanding the legal position before building at the disputed edge leaves more room to find a workable solution.
How can you establish where the legal boundary lies?
Start with your title register and plan, and any conveyance or transfer deed and its plan. If the register mentions a document marked “copy filed”, you may be able to obtain it. The wording of those documents, alongside evidence of the site's original layout, may help establish what was conveyed.
The red line on a Land Registry title plan is rarely the answer on its own. HM Land Registry explains that most title plans show a general boundary rather than its exact legal position. A fence, hedge or wall can offer a clue, but it may stand to one side of the boundary or have changed over time. Measuring the red line against your extension drawings will not settle a dispute over a narrow strip of land.
If doubt remains, a chartered land surveyor experienced in boundary disputes can assess the deeds, plans and site, as RICS explains. A property dispute solicitor can advise what the evidence means for your legal position. A surveyor's opinion may help neighbours agree, but does not itself settle a contested legal boundary.
What if the extension appears to cross the boundary?
Identify precisely what is disputed. Is it the proposed wall, a roof projection, foundations or builders needing access for scaffolding? These questions may involve ownership, possible encroachment or rights of access, each of which needs to be considered on its own facts.
Ask your designer to show the proposed structure against the contested area and share the relevant drawings. If you are the affected neighbour, explain which part concerns you and what your documents show. Proximity to a fence does not prove the extension crosses the legal boundary, but the homeowner should not assume the fence marks all the land available for building.
If the work needs access to neighbouring land, establish whether there is consent or a legal right to enter. The Party Wall Act can provide access rights for certain covered work, subject to notice and other requirements, but not for every extension project. Take advice before building on or using disputed land.
Does planning permission settle a boundary dispute?
No. Planning permission, where required, does not establish land ownership or itself give a right to build on someone else's property. Basingstoke and Deane Borough Council lists land and boundary disputes among matters its planning process cannot decide.
A neighbour may have planning concerns about an extension, such as its appearance or effect on privacy. A disagreement over who owns the ground beneath a proposed wall is a separate civil property issue. The receipt of planning permission does not mean that the applicant has the legal right to build on the land in question if the land is not owned by them.
Will a party wall notice decide where the boundary is?
No. The Party Wall etc. Act 1996 may require notice for certain work to an existing party wall, construction at the boundary or excavation near a neighbouring building. Where the Act applies and neighbours disagree about the proposed work, a party wall surveyor or surveyors may make an award dealing with matters under the Act. An award cannot decide the position of a disputed legal boundary.
There is an important distinction if you plan to build a new wall astride the boundary: the government's guidance says the adjoining owner's written consent is needed for that proposal. If consent is not given, a different design with the wall wholly on your own land may be possible, subject to the other rules that apply. The neighbour's position on a particular shared-wall proposal should therefore be considered carefully, without treating it as a veto over every possible extension.
If notice requirements are unclear, seek advice from a suitably qualified party wall professional. The boundary question needs separate property-law advice.
Can neighbours resolve the disagreement before building starts?
Discuss the deeds and drawings with your neighbour, informed by a specialist survey if needed. You may find the extension can proceed, needs altering or depends on agreeing the boundary. Negotiation or mediation can help when each side reads the evidence differently.
If both owners agree a boundary's position, a written agreement can record it and may be noted on their title registers, and this can be beneficial for all concerned to avoid future disputes. An agreement identifying the existing boundary differs from an arrangement transferring land, which may require a formal transfer. A solicitor can advise on the right document before either owner relies on it.
Where agreement is not possible, further steps may be needed. HM Land Registry supplies records and can record a determined boundary once the precise line is established, but it cannot decide a disagreement between neighbours about where that line lies. A solicitor can advise whether a determined boundary application or court or tribunal proceedings are appropriate. Get advice before committing to construction at the disputed line.
How can Lamb Brooks help?
If a neighbour claims your extension would occupy their land or challenges access for the work, early advice can clarify your position. The same applies if you are concerned about a neighbour's plans. A solicitor can assess the title documents and survey evidence or help record an agreement.
At Lamb Brooks, our Property Disputes team advises on boundaries, encroachment, access rights and neighbour disputes. We can assess the position, explore negotiation or mediation where appropriate, and advise on further action if the disagreement remains unresolved. If a boundary question is affecting your plans, contact our Dispute Resolution team to discuss the circumstances before work reaches that part of the site.
