A tree survey is a professional record of the trees on and around a site — their species, size, health, category and value — used to decide which trees should be kept and how to build without damaging them. For most UK development it follows the BS5837:2012 standard and forms the foundation of a planning application's arboricultural evidence.
The important thing to understand up front is that BS5837:2012 is a British Standard — it contains recommendations, not law. Its full title even ends in the word "Recommendations". It becomes effectively compulsory only because local planning authorities adopt it in their validation lists and impose it through planning conditions. So a tree survey is rarely a legal duty in itself; it is the thing your council asks for before it will process your application.
What a tree survey actually records
An arboriculturist walks the site and records, for every relevant tree, a defined set of attributes. These feed a schedule (a table) and, for planning, a scaled drawing.
| Attribute | What it captures |
|---|---|
| Species and age class | Common and Latin name; young, semi-mature, mature or over-mature |
| Height | Measured or estimated total height in metres |
| Stem diameter | Trunk diameter measured at 1.5 m above ground (DBH); a combined figure for multi-stem trees |
| Crown spread | Canopy radius in four cardinal directions |
| Condition | Physiological (health) and structural (soundness) assessment |
| Remaining contribution | Estimated remaining useful life expectancy |
| BS5837 category | A, B, C or U — see our tree categories guide |
| Root protection area | The below-ground zone to safeguard — see root protection area |
The root protection area (RPA) is the technical heart of the whole exercise. It is calculated as a circle with a radius of 12 times the stem diameter, capped at 707 m² (a 15 m radius) for very large trees. A tree with a 0.5 m stem diameter, for example, has an RPA radius of 6 m — roughly 113 m². Veteran and ancient trees get an enhanced RPA of 15 times the stem diameter. That circle (or a same-area polygon where rooting is provably lopsided) defines the ground you must not dig, compact or build on without a special engineered solution.
The completed survey is the raw material every later document is built on. For the full picture of what the standard produces, see what is a BS5837 tree survey and our main BS5837 tree survey page.
The situations that trigger a tree survey
You generally need a tree survey in one of these scenarios:
A planning application likely to affect trees. This is the big one. If there are trees on your site, overhanging it, or on neighbouring land with roots reaching into it, most authorities require arboricultural information before they will even validate the application. "Affecting" is broad — it includes driveways, patios, extensions, drains and utility runs, not just the building footprint.
Trees with statutory protection. If a tree has a Tree Preservation Order or stands in a conservation area, works need the council's written consent or a formal notice — separate from planning and backed by criminal law. Always run a TPO check first.
Buying or mortgaging a property with nearby trees. Lenders and surveyors sometimes flag trees close to a building over subsidence or structural concern, prompting a tree survey for a mortgage.
Managing tree safety (duty of care). A landowner must take reasonable care that trees do not injure people or damage property. Here the exercise is a tree risk assessment rather than a planning survey — a different output for a different purpose.
A neighbour or boundary dispute over overhanging branches, roots, light or safety, where an independent record settles the facts.
Discharging a planning condition. Even after permission is granted, a condition may require a detailed arboricultural method statement and tree protection plan before any work starts — usually built on the original survey data.
A worked example: a rear extension near a neighbour's oak
Say you want a single-storey rear extension, and a mature oak stands two metres over the fence in your neighbour's garden. Its trunk is 0.6 m in diameter, so its RPA radius is 7.2 m — a circle that plainly reaches well into your garden and across your proposed foundations. Even though the tree is not yours and is not being touched, the survey must record it, plot its RPA, and the arboricultural impact assessment must show the extension can be built inside that RPA without severing roots. In practice that usually means a special foundation (a piled or cantilevered design) and a hand-dug service trench, all specified in the method statement. Skip the survey and the council either invalidates the application or refuses it for want of arboricultural evidence — the single most common tree-related reason applications stall.
Why the survey should come early
BS5837 is design-led: the survey is meant to inform the layout, not to check a layout that is already fixed. Done early, it tells you which trees are worth keeping and where the constraints lie, so the scheme can be drawn around them. Done late, it often reveals that roads, foundations or services run straight through a root protection area — forcing a costly redesign or risking refusal. Surveying first is cheaper than redesigning later.
What it leads to
For a planning application, the survey is the first step in a stack of documents. Once a layout exists, the surveyor produces an arboricultural impact assessment that tests the design against the trees, plus a tree protection plan and often a draft method statement. Together these are packaged as an arboricultural report and submitted with the application. After permission, the detailed method statement and finalised protection plan are typically discharged as pre-commencement conditions before any machinery arrives on site.
Requirements are set locally — check your council
Here is the part generic guides skip: there is no single national rule that says "a tree survey is required." The requirement lives in each local planning authority's validation list, and those lists differ. One council may demand a full impact assessment and protection plan at validation; the next accepts a survey and conditions the rest for later. Trigger wording, distance thresholds, local TPO density and how strictly the tree officer applies the rules all vary authority to authority. Before you commission anything, find your council's Local Validation List (or its BS5837 guidance notes) and read the trees section.
You can see how different authorities frame this on our per-council pages — for example Leeds, Manchester, Bristol and Lambeth — each linked from the tree surveys hub. Because PlanWatch tracks live planning activity across hundreds of UK authorities, you can also watch how tree and arboricultural conditions are actually being applied to comparable applications in your area — useful evidence for what your own council is likely to expect.
Do you need one?
If your project touches, sits near, or could disturb the roots of any tree — including a neighbour's — assume you need a survey and confirm the requirement early against your local authority's validation list. If genuinely no trees are affected, you don't. When in doubt, a short conversation with a surveyor is far cheaper than an invalidated application. Ready to move? Use our directory to find a tree surveyor, or check likely fees on our tree survey cost page.
This guide covers England. BS5837:2012 applies UK-wide as a British Standard, so the survey methodology is the same across nations, but the statutory planning and tree-protection framework differs in Scotland (Town and Country Planning (Scotland) Act 1997), Wales and Northern Ireland — check your national and local guidance.