Tree Survey & Arboricultural Impact Assessment

BS5837:2012 is the British Standard titled 'Trees in relation to design, demolition and construction — Recommendations.' It sets out the methodology for surveying trees on development sites, categorising them by quality, calculating root protection areas, and designing appropriate protection measures during construction. Most planning authorities require tree surveys to comply with this standard.

It depends. Trees protected by Tree Preservation Orders (TPOs) cannot be removed without formal consent from the local authority. Trees in conservation areas require 6 weeks written notice before any work. Unprotected trees can generally be removed, but replacing significant trees is usually expected as part of the planning process. Removing trees before applying for planning permission can count against you, as the council may refuse the application on the basis of the loss.

Category A trees are high quality with an estimated remaining life expectancy of at least 40 years. Category B trees are moderate quality with at least 20 years remaining. Category C trees are low quality suitable for retention for 10 or more years, and often retained as part of landscape design rather than for individual merit. Category U trees are those in such poor condition that they cannot realistically be retained for more than 10 years and should not be a constraint on development.

The root protection area (RPA) is a calculated zone around each tree where the soil should not be disturbed by construction. It is based on the stem diameter and represents the minimum area around a tree that must be protected to ensure its survival. The RPA is typically shown as a circle on the tree constraints plan, and no excavation, storage of materials, or vehicle movements should take place within it without specific arboricultural supervision.

If there are trees on or near your property that could be affected by the extension, your local authority will likely require a tree survey. This is particularly common where trees are protected by TPOs or the property is within a conservation area. Even unprotected trees close to a proposed extension may need assessment to demonstrate that the development will not damage root systems or crown structures.

Yes, tree surveys can be carried out at any time of year. However, some aspects of tree condition assessment are better evaluated when trees are in full leaf, particularly crown density, dieback patterns, and signs of fungal infection. A winter survey may note that a follow-up inspection during the growing season is needed for certain trees. The structural elements of the survey — stem diameter, height, crown spread — are unaffected by season.

For a typical residential site with fewer than 10 trees, expect to pay between £350 and £700. If a full arboricultural impact assessment with tree protection plan and method statement is needed, costs usually fall between £800 and £1,500. The price depends on the number of trees, site accessibility, and the level of detail required by the planning authority.

A tree protection plan (TPP) is a scale drawing showing the precise locations of protective fencing around retained trees, the extent of any ground protection measures needed for construction access, and the positions of service routes, site compounds, and storage areas in relation to root protection zones. It is a practical document used by contractors on site to ensure trees are properly safeguarded during building works.

Tree loss is a significant material consideration. Planning officers will weigh the benefits of the development against the value of the trees being removed. Losing high-quality Category A trees is a serious concern and may lead to refusal. You can improve your prospects by demonstrating that tree loss has been minimised through design, proposing high-quality replacement planting, and showing that the remaining trees will be properly protected during construction.

Hedgerows are not typically included in a BS5837 tree survey unless they contain significant individual trees. However, hedgerows are protected under separate legislation — the Hedgerows Regulations 1997 — which can prevent removal of important hedgerows without consent. Your arboriculturist should note significant hedgerows in their report and may recommend a separate hedgerow assessment if removal is proposed.