UK Guide
BS5837 Tree Survey:
the Full Process
What a BS5837:2012 survey actually involves — categorisation, RPA calculation, and the documents a planning authority expects to see.
1. What BS5837 is, and when you need one
BS5837:2012 ("Trees in relation to design, demolition and construction — Recommendations") is the British Standard that governs how trees are surveyed, assessed, and protected on or near a development site. Most UK local planning authorities require a BS5837 survey as part of the validation checklist for any application where trees are present on or adjacent to the site — extensions, new-build, change of use, even some tree works applications where a TPO is in play.
The survey itself is a data-gathering exercise. It feeds two other documents: the Arboricultural Impact Assessment (AIA), which judges what the proposed development does to the trees, and — if the development goes ahead near retained trees — the Arboricultural Method Statement (AMS) and a Tree Protection Plan (TPP), which set out how those trees get protected during construction.
2. The site visit
A BS5837 survey is a visual tree survey (VTS) — ground-level, no climbing, no excavation. For each tree, stem, or group above the standard's inclusion threshold (typically anything with a stem diameter of 75mm or more, measured at 1.5m, though some authorities set their own local thresholds), you record:
- Species (common and botanical name)
- Stem diameter at 1.5m above ground level, in millimetres (for multi-stem trees, each stem measured separately)
- Height, in metres
- Crown spread in four directions, or at minimum north-south and east-west, in metres
- Height of first significant branch (crown clearance)
- Physiological and structural condition
- Estimated remaining contribution — how many more years the tree is likely to remain a benefit given its condition and life stage
- Preliminary management recommendations
Every tree gets a number, tied to its position on a topographical survey or site plan. That numbering is what everything downstream — the schedule, the AIA, the TPP — hangs off. Get the numbering wrong or lose the tie between tree and location, and the whole report has to be reworked.
Groups of trees (a hedge, a shelterbelt, a woodland edge too dense to assess individually) are recorded as a group with an averaged diameter and a single category, rather than tree-by-tree.
3. Category A/B/C/U grading
BS5837 sorts every surveyed tree into one of four categories, based on quality and value rather than size:
Category U — trees in such poor condition, or with such a short safe useful life expectancy, that removal is justified regardless of the development. Assessed and categorised first — a Category U tree doesn't need further grading.
Category A — high quality trees with a clear long-term contribution: good specimens, veteran or ancient trees, or trees with particular conservation, landscape, or cultural value.
Category B — moderate quality trees with a reasonable remaining contribution, without quite meeting the bar for Category A.
Category C — low quality trees, or trees not old or large enough to have accrued much value yet, offering only a limited contribution.
Categories A, B, and C each split further into three sub-categories — 1 (arboricultural value), 2 (landscape value), 3 (cultural or conservation value) — though in practice most surveyors record the dominant sub-category rather than all three for every tree. The category drives the colour coding on the Tree Constraints Plan (A green, B blue, C grey, U red is the convention most CAD packages default to, though the standard itself doesn't mandate specific colours) and, critically, drives which trees a planning authority will push back hard on losing.
4. Root Protection Area — the basic calculation
The Root Protection Area (RPA) is the minimum area around a tree, at ground level, that should be left undisturbed by construction to protect enough of the rooting volume for the tree to survive and remain stable. It's expressed as a circle (or an adjusted, non-circular polygon where site constraints justify moving it) with the tree's stem at the centre.
The standard calculation: take the stem diameter measured at 1.5m, convert it to metres, and multiply by 12. That gives the radius of the RPA circle, in metres. A tree with a 500mm stem diameter gets a 6m radius RPA — an area of roughly 113m². For multi-stem trees, the diameters are aggregated before the calculation, not simply added stem-by-stem.
This is the basic method — enough to understand what a category means for a site layout at concept stage. Producing the actual RPA circles on a plan, adjusting them where hardstanding or ground conditions justify a non-circular shape, and reconciling them against the proposed layout is CAD/GIS work, done by a technician using the surveyor's raw stem diameters and tree numbers as input.
5. Veteran trees and TPOs
Two things run alongside the BS5837 category but aren't the same thing, and it's worth recording both explicitly rather than letting them blur into the category field. A Tree Preservation Order (TPO) is a legal designation from the local planning authority protecting a specific tree, group, or woodland — it exists independently of BS5837 and independently of the tree's category. A Category C tree can carry a TPO; a Category A tree might not. Check the local authority's TPO register before the survey, not after, since a TPO changes what's legally required before any works.
A veteran tree — one showing the characteristics of great age relative to its species (significant girth, cavities, deadwood, a particular growth form) — is a separate flag entirely, usually recorded as a note alongside its category rather than a category of its own. Veteran trees typically pull toward Category A regardless of their physical condition, because their value is as much about age and habitat as about vigour. Local planning policy and national guidance both treat veteran tree loss as something requiring strong justification, so flagging it clearly in the survey data protects the tree and protects your report from a validation challenge.
6. What a surveyor delivers: AIA, AMS, TPP
A validated planning application involving trees typically needs three connected documents, in roughly this order:
Tree survey schedule + Tree Constraints Plan — the raw data (species, dimensions, category, condition, RPA) as a table, plus a plan showing every tree number, category colour-coding, and RPA circle against the existing site.
Arboricultural Impact Assessment (AIA) — assesses the effect of the proposed layout on the retained trees: what falls inside an RPA, what needs removing to make the scheme work, and whether the loss is justified.
Arboricultural Method Statement (AMS) + Tree Protection Plan (TPP) — required once a scheme is approved and near retained trees: how protective fencing gets installed, where no-dig construction is specified within an RPA, where site access and material storage are permitted, and a monitoring schedule for the build.
7. Why surveys get rejected at validation
Most rejected submissions aren't rejected because the survey work was bad — they're rejected because something didn't match. A tree number on the schedule that doesn't appear on the plan. An RPA that overlaps the proposed footprint with no comment in the AIA. A category assigned in the field that doesn't match the justification text. Missing stem diameters on trees just outside the site boundary that still influence the assessment.
The common thread: the survey, the plan, and the written assessment were produced at different times, sometimes by different people, and the numbering or data drifted between them. Keeping the tree number as the single consistent key across every document is the single highest-leverage habit in this workflow.
8. Where a field capture tool fits
LogLog handles the site-visit half of this workflow, not the CAD half. Load the topographical survey or site plan PDF, drop a numbered pin on each tree as you walk it, and record species, stem diameter (LogLog stores this as DBH in centimetres, including a comma-separated list for multi-stem trees), condition, and preservation category — A, B, C, or U — directly against that pin. Attach photos while you're standing at the tree, not later from memory.
What LogLog does not do: it doesn't draw RPA circles, it doesn't produce a Tree Constraints Plan, and it doesn't export to DWG or shapefile. The export is a ZIP — a spreadsheet (CSV and Excel), the annotated site plan with your tree pins baked in, a PDF summary sheet, and every photo named by tree number. That's the input a CAD technician needs to build the Tree Constraints Plan and TPP — clean, numbered data instead of a stack of field notes and a marked-up printout to retype.
Related: Category A/B/C/U glossary entry, Root Protection Area glossary entry, BS5837 use case. Coming off OTISS or a GPS survey app? See LogLog vs OTISS, or check pricing.
Works in any mobile browser. No DWG or shapefile export — data leaves as CSV, Excel, and PDF.