Trees on neighbouring land that overhang your site

A neighbour's tree overhanging your development site has to appear in the tree survey, and the reason is not the branches. It is the roots. A mature oak on the far side of a fence can have a root protection area extending 12 or 14 metres into your plot, which is enough to sit under the whole footprint of a new house. Leaving it out of the survey because it is outside the red line is the single most common reason an arboricultural report gets sent back.

Officers know this and check for it. A survey that stops at the boundary reads as incomplete before anyone looks at the categories.

Why offsite trees have to be surveyed

The British Standard on trees in relation to design, demolition and construction expects the survey to cover trees on the site and trees on adjacent land where they could influence the development or be influenced by it. That means any tree whose canopy, root protection area or shade reaches the site.

Root protection areas are calculated from stem diameter. For a single stemmed tree the radius is twelve times the diameter measured at 1.5 metres above ground, with the resulting area capped at just over 700 square metres for the largest trees. Run that calculation on a 700 millimetre diameter beech and the radius comes out beyond eight metres, in every direction, from a trunk that may be standing a metre the wrong side of your fence.

The practical consequence is a constraint plan that shows a shaded area over part of your plot before the house is drawn. Better to know that at the sketch stage than after the foundations are priced.

Access for survey and what to do without it

There is no right to enter a neighbour's land to survey their tree. The Access to Neighbouring Land Act 1992 allows a court to order access for basic preservation works to your own property, and it is not a route to an arboricultural inspection.

So ask. A short letter explaining that a survey is needed, that nothing will be cut, and that the neighbour will receive a copy is usually enough. Offering the report tends to work better than offering money.

Where access is refused, the survey is done from within your own boundary and from public land. An experienced arboriculturist can estimate stem diameter reliably from a measured distance, identify species, assess visible crown condition and record the canopy spread. What cannot be done is a close inspection of the base, an assessment of basal decay, or any decay detection work.

Record exactly that. The report should state which trees were inspected from a distance, from where, on what date, and what could not be assessed. A recorded limitation is a professional judgement. An unstated limitation looks like an oversight.

Root protection areas that cross a boundary

The calculated area is a starting shape, not a fixed circle. The standard allows the root protection area to be reshaped where there is sound evidence that roots have not grown in a particular direction, provided the total area is maintained.

Good reasons to reshape include an existing building with deep foundations, a road construction with a compacted sub-base, a river or a retaining wall, or a documented service trench. A fence line is not a reason. Nor is a change of ownership.

The evidence matters. Where the reshaping is material to the layout, trial pits or air spade investigation within your own land will show where roots actually are, and that evidence carries far more weight with an officer than an assertion that roots are unlikely to have crossed.

Where the area cannot be reshaped away from your footprint, the choices are a no dig construction, a foundation designed to avoid root severance, moving the building, or asking the neighbour to agree to works to the tree. The last of those is a negotiation with no legal lever behind it.

The right to cut back an overhang

You may cut branches and roots that cross your boundary, back to the boundary line and no further. You may not enter the neighbour's land to do it without permission. The material you cut belongs to the tree's owner, so it should be offered back rather than dumped over the fence.

Three limits on that right are worth knowing. Cutting so heavily that the tree dies or becomes unstable can expose you to a claim. Cutting the roots of a tree on shrinkable clay can alter ground movement under your own building as much as under theirs. And if the tree is protected, the right to abate an overhang does not remove the need for consent, because the statutory exemptions are read narrowly and a nuisance in the legal sense is more than an inconvenience.

Where you do want crown work, specify it properly rather than asking for the tree to be "cut back", and the note on specifying crown work so contractors price it correctly sets out how.

Protected trees on someone else's land

A tree preservation order attaches to the tree, not to the owner, and it binds you as much as the neighbour. So does the notice requirement for trees in a conservation area, which needs six weeks written notice to the local planning authority before work starts.

That cuts two ways on a development site. You need consent for anything you propose to do to the overhanging parts. But the protection also works in your favour, because a neighbour who objects to your scheme cannot respond by felling the tree you designed around.

Check the designation before you draw. Local authority mapping shows orders and conservation area boundaries, and an order made in 1974 on a tree that is now in three separate gardens is still in force.

Designing around a tree you cannot survey

Where access has been refused and the tree is close, design on precautionary assumptions. Take the larger plausible stem diameter. Apply the full unreshaped root protection area. Assume the canopy will grow. Then check whether the scheme still works.

Two design responses do most of the heavy lifting. A no dig construction using a cellular confinement system above existing grade takes driveways, paths and parking out of the equation. And a pile and beam or suspended slab foundation avoids the volume of excavation a trench fill footing needs, though on shrinkable clay the depth required near a tree is driven by the warranty provider's guidance rather than by arboriculture.

Drainage is the part that gets forgotten. Soakaways, attenuation and new connections all excavate within root protection areas, and the note on trees, soakaways, sewers and root ingress covers the technical ground that arguments turn on.

Recording the limitation honestly

A tree survey that deals with offsite trees properly contains: every tree within influencing distance whether inside or outside the site, the basis on which each was assessed, the stem diameters with a note where estimated, root protection areas plotted on the layout, any reshaping with the justification, the constraints on the development, and a clear statement of what could not be inspected and why.

Add a recommendation for what happens if access is later granted. Offering an inspection before work starts on site, secured by condition, gives the authority a route to approval without pretending the survey is complete. That approach fits with the wider point in the note on discharging a tree protection condition without delay.

Arboricultural reports are documents councils expect from a suitably qualified author, and professional review before submission is strongly advised. Enter your postcode on PlanScope to see which tree reports your plot is likely to need.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.