Tree surveys where the site cannot be accessed

A tree survey carried out from outside the boundary can still support an application, provided the estimated values are identified as estimates and the root protection areas are calculated on the cautious side of the estimate. What sinks these surveys is not the absence of access. It is a schedule that presents measured and estimated figures in the same column without saying which is which.

The other thing worth knowing early: there is no right of access to a neighbour's land to survey a tree for a planning application. The Access to Neighbouring Land Act 1992 is limited to works reasonably necessary for the preservation of land or buildings, and a development survey does not qualify.

Why access gets refused

Usually one of four reasons, and the reason shapes the response.

A neighbour opposed to the development in principle will refuse access to slow it down. A neighbour who is indifferent may simply not reply to a letter. An institutional owner, a utility, a railway undertaker or a highway authority often has a process that takes longer than the project programme allows. And on some sites the trees stand on land in unknown or absent ownership, where there is nobody to ask.

Where the trees are on highway land or railway land, go through the asset owner's formal process rather than the site manager, and expect a permit and a method statement for anything involving working at the boundary. Where ownership is unknown, a Land Registry search and a note of the result belongs in the report.

What can be recorded from outside the boundary

More than people assume. From adjacent land or the public footway, with a laser rangefinder, a clinometer and a camera, a competent arboriculturist can record:

• Species, and often cultivar where the form is distinctive.
• Height, measured by clinometer or rangefinder with the usual accuracy for the method.
• Crown spread at the cardinal points, measured to the drip line where it is visible.
• Crown clearance above ground level.
• Age class and an assessment of form.
• Visible condition: deadwood, cavities, bark damage, fungal brackets on the visible side, previous pruning, included unions, lean, and the condition of the crown as seen from one aspect.
• Ground conditions in the visible part of the rooting zone, including surfacing, levels and signs of previous excavation.

What cannot be recorded is anything requiring the far side of the stem, the stem base, or a measurement at 1.5 metres on an inaccessible trunk. Fungal fruiting bodies on the hidden side, basal decay, root plate movement and the real extent of a cavity all fall into that category, and a survey that is silent on them should say that it is silent on them.

Aerial imagery and published tree canopy or terrain datasets help with crown spread on larger sites, particularly where a group runs along a boundary. Use them to supplement the ground survey rather than to replace it, and say which you used.

Estimating stem diameter and root protection areas

Stem diameter is the measurement that matters, because the root protection area under BS 5837:2012 is derived from it: a radius of twelve times the stem diameter for a single stem tree, with the resulting area capped at 707 m².

Where the stem cannot be reached, the estimate can be built in two ways. The first is by direct optical measurement, using a rangefinder with a diameter function or photogrammetry from two known positions. The second is by inference from the height, crown spread and species, using the surveyor's experience of comparable trees. The second is less accurate and should be labelled as such.

Then apply the estimate cautiously. If the diameter is estimated at 500 to 600 millimetres, calculate the root protection area on 600, not on the midpoint. An under-sized root protection area that turns out to be wrong after access is granted produces a redesign at the worst possible moment, and it is the single most common reason a limited survey costs more than it saved. The practical consequences of getting this wrong show up in the detailing, as retaining walls and level changes in a root protection area illustrates.

Record both the estimate and its basis in the schedule, with a column for the method. Three values, one measured and two estimated, with the method named against each, is a defensible schedule. A single number with no provenance is not.

Stating the limitations so the report carries weight

BS 5837:2012 expects the survey report to record what was done, when, and with what constraints. Treat that as the most important page in the document rather than boilerplate at the back.

Set out, in plain terms:

1. The date, the weather and whether the trees were in leaf.
2. Which trees were inspected from within the site, which from adjacent land and which from the street only.
3. The aspect from which each off-site tree was viewed, and what that aspect prevented seeing.
4. The instruments used and the accuracy claimed for each measurement type.
5. The access that was sought, from whom, when, and the response.
6. What would change if access were later granted, item by item.

Point six is the one that persuades officers. A limitations section that says "access was not available" tells the reader nothing. One that says the stem diameters of trees T7 to T11 are estimated, that the root protection areas have been calculated on the upper bound of the estimate, and that confirmation of the measured diameters could only reduce those areas, tells the reader that the design has no downside risk from the uncertainty.

How councils treat a limited survey

Variably, and mostly on whether the limitation affects the decision. Where the trees are peripheral, the root protection areas have been drawn generously and no development is proposed within them, a limited survey is usually accepted without comment.

Where the layout depends on working close to an off-site tree, expect the tree officer to say the information is insufficient to assess the impact. That is a reasonable position and the answer is to change the layout, not to argue about the survey. A scheme that needs a measured diameter it cannot obtain is a scheme designed on an assumption.

Validation is a separate question. An authority can only refuse to validate for information on the national list or its own published local list, so a demand for a full measured survey of off-site trees as a validation requirement is worth testing against the published checklist. Winning that argument gets the application registered. It does not win the planning decision, and the two should not be confused.

Surveys for demolition-only proposals raise a related set of problems, covered in tree surveys for demolition-only proposals.

Requesting access formally and recording the refusal

Write, do not telephone. A short letter to the registered owner, sent by post and email where available, setting out:

• Who will attend, their qualifications and their insurance position.
• What they will do, for how long, and that no works to the tree are proposed.
• Two or three alternative dates, at least two weeks ahead.
• A note that access is being sought so that the trees can be properly assessed and protected.

Keep the letter, the proof of posting and any reply. Where there is no response, send one reminder and then record the position. That file becomes part of the limitations section and, if the matter reaches appeal, part of the evidence that the applicant behaved reasonably. The way arboricultural material is handled at that stage is set out in arboricultural evidence at appeal.

Two things not to do. Do not survey from inside the neighbour's boundary without permission, because trespass undermines everything else in the report. And do not cut overhanging branches to improve the view of a stem: the common law right to abate an encroachment does not extend to works that need consent under a Tree Preservation Order or a section 211 notice in a conservation area.

Conditions that deal with the remaining gap

Where some uncertainty remains, offer the condition rather than waiting for it. Wording that works in practice covers three things: an updated survey and arboricultural method statement to be submitted once access is obtained or before any work within a stated distance of the boundary, approval of tree protection details before development begins, and arboricultural supervision at defined hold points.

Offering that in the tree survey and method statement you submit shows the officer that the gap is managed rather than ignored, which is usually the difference between a request for further information and a recommendation.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. Arboricultural survey work is something councils expect from a suitably qualified author, and professional review is strongly advised.

To scope the arboricultural and landscape documents a site needs, enter your postcode on PlanScope and work through the constraints it detects. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.