How long a BS 5837 tree survey stays valid

BS 5837:2012 does not set an expiry date for a tree survey. Local planning authorities do, informally, and most validation checklists expect a survey carried out within the last twelve months, with some accepting up to two years on a stable site. What matters is whether anything material has changed since it was written, rather than the age of the document, and on a site with ash, or after a bad winter, the answer can be yes within a single season.

Why authorities expect a current survey

A tree survey supports two different decisions and both need current data.

At validation, the officer is deciding whether the application can be assessed. A survey that predates a significant change on site, or that lists trees which are no longer there, cannot support the impact assessment built on it.

At pre-commencement, the tree officer is deciding whether the protection measures are still right for the trees as they now stand. Root protection areas that have grown, a retained tree that has declined into category U, or a neighbour's tree that has been felled all change the answer.

The survey itself is the foundation for everything else, as the tree survey page sets out, and councils usually expect a suitably qualified arboriculturist as its author with professional review before submission.

Check the local validation list rather than assuming twelve months. Some authorities state a period, some require the survey to be dated within the current or previous calendar year, and a few say only that it must be current, which leaves the judgment with the case officer.

What ages a survey fastest

Five factors, in rough order of how quickly they bite.

• Disease, particularly ash dieback, which can take a tree from apparently healthy to structurally unsound within two or three seasons.
• Storm damage, which is a single-event risk rather than a gradual one.
• Third party works, including felling and heavy pruning on neighbouring land that changes exposure and crown form.
• Growth, which alters stem diameter and therefore root protection areas.
• Changes to the site itself, such as level changes, service trenches or compaction from parked vehicles.

A site with a large ash population should be treated as having a short survey life. Managing ash dieback is now a routine part of site appraisal, and a survey from three years ago on a site with mature ash tells you very little about what is standing today.

Conversely, a survey of six mature oaks in a walled garden with no site activity since may be perfectly reliable at two years old, and a well-argued covering letter saying so will often be accepted.

Growth and the root protection area

This is the change people forget, because it is invisible and arithmetical.

BS 5837:2012 sets the root protection area for a single stem tree as a circle with a radius of twelve times the stem diameter, measured at 1.5 metres above ground level, with the area capped at 707 square metres.

A young or semi-mature tree putting on a centimetre of stem diameter a year increases its root protection area radius by twelve centimetres a year. Over a five-year gap between survey and commencement, that is sixty centimetres of extra radius, which on a constrained site is the difference between a foundation that works and one that does not.

The effect is largest on the trees most likely to be retained near new buildings, because those are the semi-mature ones with the best future. Mature trees put on less diameter and are closer to the cap.

Where the survey is more than a couple of years old and a building sits close to a retained tree, remeasure the stems. It is an hour's work and it can save a redesign at foundation stage, particularly where the drainage layout is also tight against the root zone, which brings its own constraints as set out in trees, drainage, soakaways and root ingress.

Storm damage and sudden change

A named storm is a reason to revisit a survey regardless of its age.

Wind damage is not always visible as a lost limb. Partial root plate failure shows as a slight lean, a raised soil crack on the windward side or a depression on the leeward side, and it can be missed by anyone not looking for it. A tree that has lost a substantial part of its crown has an altered wind loading and a changed future.

After a major storm event, walk the site with the arboriculturist and record what you find with dated photographs. If the change is limited, an addendum letter will do. If several trees are affected, expect a resurvey.

The same applies where a neighbouring site has been cleared. A tree that grew within a group and is suddenly standing alone is exposed to loads it never carried before.

Seasonal limits on inspection

A ground level visual assessment can be carried out at any time of year, and a BS 5837 survey is not a summer-only exercise.

Some things read better in one season than another. Deadwood, crown architecture and structural defects are clearer in winter with the leaves off. Foliage density, dieback, leaf scorch and the symptoms of many pathogens are only assessable in leaf. Fungal fruiting bodies are most visible in autumn.

That means a survey carried out in February may need a leaf-on check before conclusions about vitality are relied on, and the report should say so rather than leaving the reader to guess.

Say what the limitations were. A survey that records the date, the weather, the access constraints and anything not inspected is a survey an officer can rely on. One that reads as though every tree was examined in ideal conditions invites a question.

Updating rather than repeating

A full resurvey is rarely necessary. What is usually needed is an update, and the distinction is worth making explicitly in the fee proposal.

An update note should contain seven things.

1. The date of the update inspection, the surveyor and their qualification.
2. Reference to the original survey by title, date and revision.
3. The trees inspected, and confirmation that they are the trees material to the scheme.
4. Changes since the original survey, tree by tree, including removals by others.
5. Remeasured stem diameters and revised root protection areas where these have changed.
6. Confirmation or amendment of each category, with reasons for any change.
7. The implications for the approved tree protection plan and method statement.

Issue it as a revision to the original schedule rather than as a standalone document, so that the drawings and the schedule stay coherent. Losing version control between an original survey, an update note and a protection plan is the surest way to produce a condition discharge that takes three attempts, as the note on discharging a tree protection condition without delay explains.

Pre-commencement checks

Many permissions carry a condition requiring an arboricultural check or a site meeting before works begin. Read it carefully, because the wording varies more than it should.

A condition requiring an updated survey is different from one requiring the protective fencing to be inspected, which is different again from one requiring a pre-start meeting with the tree officer. Only the first needs a new inspection report, and submitting one where a site meeting was required wastes a fortnight.

Where crown work is proposed as part of the update, specify it properly so contractors price the same thing, using the approach in specifying crown work so contractors price it correctly.

As an illustrative example, a permission granted in spring 2022 is implemented in autumn 2026. The survey is four and a half years old, the site contains two mature ash and a semi-mature lime three metres from the proposed extension. The ash need reassessment because of disease progression, the lime needs its stem remeasured because the root protection area will have grown, and the remaining trees can be confirmed by inspection. One visit, one addendum, no redesign.

To see which tree and landscape documents your project is likely to need, enter your postcode on PlanScope.

This is general guidance, not legal advice, so 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.