The tree schedule in an arboricultural impact assessment
The tree schedule is the part of an arboricultural impact assessment an officer checks line by line. Here are the BS 5837 fields, the measurement conventions and the errors reviewers find.
The tree schedule is the part of an arboricultural impact assessment a planning officer actually reads line by line. Everything else in the document interprets it. If the schedule is incomplete, the categories unexplained or the root protection areas missing, the assessment cannot be checked and the tree officer will ask for it again, usually three weeks into the consultation period.
BS 5837:2012 sets out what each entry has to record. The fields are not optional extras and they are not interchangeable with whatever a survey app happens to export.
What the schedule has to record for each tree
One row per tree, with these columns:
- reference number, matching the tag on site and the position on the plan
- species, given in full rather than abbreviated
- height in metres
- stem diameter in millimetres, measured at 1.5 m above ground level
- branch spread, recorded as crown radius at the four cardinal points
- height of crown clearance above adjacent ground level
- age class: young, middle aged, mature, over-mature or veteran
- physiological condition and structural condition, recorded separately
- preliminary management recommendations
- estimated remaining contribution in years, in the bands under 10, 10 plus, 20 plus and 40 plus
- retention category with subcategory
Two of those are regularly collapsed into one and should not be. Physiological condition describes vitality: foliage density, extension growth, dieback. Structural condition describes integrity: cavities, included unions, decay, lean, root plate movement. A tree can be structurally sound and physiologically poor, and the management recommendation differs completely.
Stem diameter measurement conventions
Stem diameter drives the root protection area, so the measurement convention matters more than any other field in the table.
The standard measurement is at 1.5 m above ground level. Where the tree stands on a slope, measure from the higher side of the ground. Where the stem forks below 1.5 m, take the measurement immediately below the fork rather than through the union.
Multi-stemmed trees follow a specific rule. For a tree with fewer than five stems, the diameter used is the square root of the sum of the squares of each stem diameter. For five or more stems, take the five largest and apply the same calculation. Recording the largest stem only, or adding the diameters together, produces a root protection area that is either far too small or far too large, and both errors are visible to a reviewer with a calculator.
State the method in a note under the schedule. It takes one sentence and removes an argument.
Crown spread and height recording
Crown radius at four cardinal points, not a single average figure. The asymmetry is the point: a tree with a 2 m radius to the north and 9 m to the south has a shade pattern and a canopy constraint that an averaged 5.5 m figure hides entirely.
Record crown clearance as well, because it determines whether the canopy conflicts with the proposed building, with vehicle access or with nothing at all. A mature lime with 7 m of clear stem is a different design constraint from the same tree with branches at 2 m.
Heights can be estimated with a clinometer or a measuring rule and should be stated as approximate. Nobody expects millimetre accuracy on a 22 m tree, and claiming it undermines confidence in the rest of the sheet.
Retention categories and subcategories
The categories are U, A, B and C, and the subcategory numbers describe why the tree has value.
| Category | Meaning | Remaining contribution |
|---|---|---|
| U | Cannot realistically be retained as a living tree in the context of the current land use | Under 10 years |
| A | High quality | 40 years or more |
| B | Moderate quality | 20 years or more |
| C | Low quality, or young trees below 150 mm stem diameter | 10 years or more |
Subcategory 1 covers mainly arboricultural qualities, 2 mainly landscape qualities including screening and visual amenity, and 3 mainly cultural values including conservation and historic interest. A tree can carry more than one subcategory, and the combination is written as A1, B2 and so on.
But category U is the one most often misused. It means the tree cannot be retained for arboricultural reasons, whatever the development does. It does not mean the tree is inconvenient, and an officer who finds an otherwise healthy category B oak listed as U will treat the whole schedule with suspicion. Be straight about which trees are being removed for development reasons rather than condition reasons, because that is an honest planning argument and a dishonest category is not.
Root protection areas in the same table
Put the root protection area in the schedule as well as on the plan. For a single-stemmed tree it is the area of a circle with a radius of 12 times the stem diameter, with the area capped at 707 m2.
Three columns do it cleanly: calculated radius in metres, calculated area in square metres, and a note where the area has been modified. Modification is allowed where soil conditions, existing structures or hard surfaces mean the roots cannot be present in the notional circle, but a modified root protection area has to retain the same area, shifted rather than reduced, and the reasoning belongs in the notes column.
An offset root protection area without stated justification is the single most common reason a tree officer objects to an otherwise competent assessment.
Groups, hedges and woodland entries
Not everything is an individual tree. BS 5837 allows groups where trees function together, recorded with a group reference such as G1, and the entry describes the group's composition, the range of sizes and a single category.
Hedges take an H reference and should record species composition, length, height and width, together with whether the hedge may be an important hedgerow under the hedgerow regulations. Woodland takes a W reference, with an indication of the dominant species, structure and age range.
The decision about what to group matters. Grouping 14 individual trees along a boundary as G1 saves survey time and loses the ability to argue that nine of them can stay. Where any tree in a group might be affected individually, survey it individually.
Linking the schedule to the constraints plan
The schedule and the tree constraints plan are one document in two forms, and they have to agree. Every reference on the plan appears in the schedule. Every root protection area drawn matches the calculated area. Shade patterns, where plotted, use the recorded crown radii rather than a notional circle.
Where the layout encroaches, the impact assessment then quantifies it: the percentage of each root protection area affected, what causes the encroachment, and what mitigation applies, whether no-dig construction, a cantilevered foundation or a revised building line. Officers accept encroachment with evidence far more readily than they accept a drawing that pretends there is none.
An Arboricultural Impact Assessment is a report councils expect from a suitably qualified author, normally a consultant arboriculturist, and professional review is strongly advised before submission. A tree survey and Arboricultural Impact Assessment drafted on PlanScope sets out the schedule structure, the categories and the impact sections with the measured fields left for the surveyor to complete. The retained trees then feed the Landscape Strategy, the habitat baseline in a Biodiversity Net Gain Assessment and the design reasoning in the Design and Access Statement. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.
Frequently asked questions
Where is stem diameter measured for a BS 5837 survey?
At 1.5 m above ground level, taken from the higher side where the tree stands on a slope. Where the stem forks below 1.5 m, measure immediately below the fork rather than through the union. The figure drives the root protection area, so the convention used should be stated in a note under the schedule.
How is a multi-stemmed tree measured?
For fewer than five stems, the diameter used is the square root of the sum of the squares of each stem diameter. For five or more stems, apply the same calculation to the five largest. Adding diameters together or recording only the largest stem produces a root protection area that is clearly wrong to any reviewer.
What does category U actually mean?
That the tree cannot realistically be retained as a living tree in the context of the current land use for more than ten years, for arboricultural reasons. It does not mean the tree is in the way. Listing a healthy category B tree as U to justify removal undermines the credibility of the entire schedule.
How large is a root protection area?
For a single-stemmed tree it is the area of a circle with a radius of 12 times the stem diameter, with the area capped at 707 square metres. It can be offset where soil conditions, structures or hard surfaces mean roots cannot be present, but the same area must be retained and the reasoning recorded.
When should trees be surveyed as a group rather than individually?
Only where they function together and will be treated together. Grouping a boundary line of trees saves survey time but removes the ability to argue that some can be retained while others go. If any tree within a potential group might be affected individually, give it its own reference and row.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.