Specifying tree works to BS 3998 in a consent application

A BS 3998 tree works specification should read like an instruction to a contractor, not a wish. Most refusals and most requests for further information on applications to work on protected trees come down to wording that cannot be measured: reduce by a third, tidy up, cut back from the building. A tree officer cannot grant consent for that, because the consent would authorise almost anything and could never be enforced. Specify the finished dimensions of the tree instead, operation by operation, in the vocabulary BS 3998 uses.

That applies whether the tree sits under a Tree Preservation Order, which needs a consent application under the Town and Country Planning (Tree Preservation) (England) Regulations 2012, or in a conservation area, where section 211 of the Town and Country Planning Act 1990 requires six weeks' notice before the works.

Why a vague specification is refused

A tree officer assessing an application has to decide whether the proposed work is acceptable for the amenity value the protection exists to defend. They cannot do that without knowing what the tree will look like afterwards.

Consent is also granted for the works applied for and nothing else. Carrying out something different, even something less severe, can be a breach. So a loose specification harms the applicant as much as the authority: the contractor interprets it one way, the officer visits and reads it another, and the argument happens after the saw has been used.

The third reason is appeal. A refusal can be challenged, and the inspector will look at the works as specified. An application that cannot be pinned down cannot be defended.

The operations the standard recognises

Use the standard's own terms, and one term per line of the schedule.

• crown reduction, meaning a reduction in the overall height or spread of the crown
• crown lifting, meaning removal of the lowest branches to a stated height above ground level
• crown thinning, meaning removal of a proportion of secondary branches throughout the crown while keeping its size and shape
• crown cleaning, meaning removal of deadwood, broken branches, climbing plants and other unwanted material
• formative pruning on young trees
• pollarding and the subsequent management of pollards
• coppicing
• removal of epicormic growth
• root pruning or root severance, usually linked to construction
• selective branch removal, where a named limb is to be taken back to a stated point
• felling, which is not pruning and should be described separately with its own justification

Avoid words the standard does not use. Topping, lopping, dressing back and shaping all appear on applications and none of them means anything precise.

Writing a crown reduction that can be measured

State the dimensions the crown will have when the work finishes. The standard's approach is to describe the remaining crown rather than the material removed.

So the wording is: reduce the overall height of tree T4 from approximately 13 metres to 10.5 metres, and reduce the lateral spread on the southern aspect from approximately 7 metres to 5 metres, cutting back to suitable secondary growth points and leaving no final cut exceeding 50 millimetres in diameter. Add that cuts are to be made outside the branch collar and that no cut is to be flush with the parent stem.

Three further details make the difference between a specification an officer can approve and one they query.

1. Name the aspects. Reductions are rarely uniform, and a tree reduced only on one side needs saying so, with the compass direction or the feature it faces.
2. Give the pre-works dimensions as measured, flagged as approximate, so the extent of the change is visible without a site visit.
3. Cap the final cut diameter, which controls severity far better than any overall figure.

Where the tree is already in decline, say what the reduction is intended to achieve, because the case for a heavier reduction rests on the condition of the tree rather than on convenience. Ash is the obvious instance, and what ash dieback changes in a tree survey feeds directly into the justification for works.

Crown lifting and thinning described properly

Crown lifting is specified as a height above ground level, measured at the base of the tree, and it should state what the clearance is for.

Crown lift tree T7 to 5.3 metres above ground level over the adopted carriageway and to 2.5 metres over the footway, by removing or shortening the lowest secondary branches. Do not express a lift as a number of branches, and do not lift so far that the live crown is pushed into the upper part of the tree, since removing too much of the lower crown raises the centre of gravity and leaves a top-heavy specimen that is harder to manage later.

Thinning is the one operation conventionally expressed as a proportion. Even then the wording needs more than a figure: thin the crown of T2 by 20 per cent of the leaf-bearing canopy, removing secondary and tertiary branches evenly throughout the crown, retaining the existing height and spread. Figures much above 30 per cent are difficult to justify on a mature tree and tend to be refused or reduced.

Both operations are frequently proposed to clear construction access, and where the real driver is a crane or scaffold, the application should say so and cross-refer to the method statement for oversail over a protected tree.

Why a percentage on its own fails

Reduce by 30 per cent is the single most common phrase on these applications and it means nothing. Thirty per cent of what: height, spread, canopy volume, leaf area, branch length? A contractor given that instruction on a 15 metre oak could remove 4.5 metres of height, or take a third of the branch length everywhere, or thin a third of the canopy. Those are three different trees.

Percentages also hide severity. A reduction expressed as a modest percentage can still involve cutting into mature wood beyond any suitable growth point, which is the kind of pruning that causes decay and dieback.

So use percentages only for thinning, and only alongside the wording that fixes what stays. For everything else, give the finished dimensions.

Timing, nesting birds and bats

Protection under a Tree Preservation Order says nothing about wildlife, and consent to carry out works is not a defence to a wildlife offence.

Nesting birds are the usual constraint. It is an offence under section 1 of the Wildlife and Countryside Act 1981 to damage or destroy the nest of a wild bird while it is in use or being built, so works in the main breeding season from March to August need a pre-works check by a competent person and a method for stopping if an active nest is found. Many authorities impose this as a condition on consent.

Bats raise the stakes. Where a tree has potential roost features such as hollows, loose bark, rot holes or large limb tears, assessment by a suitably licensed ecologist is needed before work, and a licence may be required under the Conservation of Habitats and Species Regulations 2017. That is a legal requirement rather than a matter of good practice, and the licensed ecologist is the only person who can discharge it.

Species also affects timing. Heavy pruning of birch and walnut in spring causes bleeding, and stone fruit species are usually pruned in summer to reduce the risk of silver leaf infection. Put the window in the specification rather than leaving it to the contractor's diary.

Drawings, tree numbers and the application itself

Every tree in the specification needs a number that matches the tree survey schedule and the plan. Inconsistent numbering between the survey, the works schedule and the application form is a validation issue in its own right, and it is avoidable.

Submit a tree works plan showing each tree's position and number, the extent of the proposed reduction where it is directional, and any access route or protective fencing. Where the application is on behalf of an owner whose tree overhangs a neighbour, confirm ownership and the extent of the applicant's interest, since trees on a boundary raise consent questions of their own.

Finally, give reasons for each operation. The 2012 Regulations expect the application to say why the work is wanted, and an arboricultural reason, such as removing a hazardous limb identified in the survey, carries more weight than an amenity preference. Keep the reason next to the operation in the schedule rather than in a covering letter.

This is general guidance, not legal advice; 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.