Why trees need protecting during building work
Most tree damage on building sites happens below ground and out of sight. Digging foundations or trenches cuts roots, vehicles compress the soil over them, and stored materials or spilled cement can poison them. The tree may look fine for a year or two and then decline. Planning authorities therefore often make tree protection a condition of permission, and the tree survey they ask for is expected to follow the British Standard for trees and development, BS 5837 (Trees in relation to design, demolition and construction). The government's planning advice on ancient woodland and veteran trees refers to BS 5837 in exactly this way.
The key documents
- Tree survey
- An arboriculturist records every tree that could be affected, its size, condition and how long it is likely to last, so the layout can be planned around the best ones. See also our tree surveys page.
- Root protection area (RPA)
- The minimum area around a tree that BS 5837 treats as needing protection so the tree stays viable. It is calculated from the trunk diameter and centred on the base of the stem. Building work inside it is avoided or specially controlled.
- Arboricultural impact assessment (AIA)
- A report that sets the proposed development against the trees, showing which will be kept, which need to go, and where the design conflicts with root protection areas.
- Arboricultural method statement (AMS)
- Explains how any work close to or inside an RPA will be done, for example by hand digging, no-dig surfacing, or special foundations, and who will check it.
- Tree protection plan (TPP)
- A scaled drawing showing where the fencing and ground protection must go.
Fencing and ground protection
Protective barriers are normally put up before any machinery or materials arrive and stay in place until work is finished. The aim is to keep people, vehicles, storage and spoil out of the protected area. Where access across a root area is unavoidable, a tree surgeon or groundworks firm can lay ground protection, such as boards or a purpose-made mat system over a protective layer, to spread the load. Fencing should not be moved or removed without the agreement of the person named in the method statement and, usually, the council.
Supervision and site monitoring
Many planning conditions ask for an arboriculturist to inspect the fencing before work starts and to visit during key stages, such as excavation near roots, and to keep a written record. Ask the firm whether it offers this, how many visits it would expect, and who signs off compliance for the council.
Protected trees, conditions and breaches
Trees on a development site may also be protected by a Tree Preservation Order or conservation area status. See our TPO and conservation area guide. Damaging a protected tree is a criminal offence. Under section 210 of the Town and Country Planning Act 1990 the fine is unlimited, whether the case is heard in the magistrates' court or the Crown Court, and the court must take into account any financial gain from the offence. Councils can also take enforcement action over breaches of planning conditions that require physical tree protection.
Who needs it and when
The need usually arises at the planning stage. A householder building an extension, a self-builder, a developer or a farmer converting a barn may all be asked for tree information with the application, and a condition on the permission may then require the fencing and method statement before any work begins. If a condition says "prior to commencement", the details generally have to be approved by the council before anyone digs or brings plant onto the site, so it pays to arrange the survey early. Ordinary garden work, such as a shed or a path, may not need any of this, but roots can still be harmed, so ask a tree surgeon if a valued tree is close by. A building plot with an ancient woodland edge or veteran trees is likely to need a larger buffer, as the government's planning advice explains.
Questions to ask a firm
- Will the work follow BS 5837, and has the firm prepared reports that councils accepted before?
- Can they supply, install and inspect the fencing, or only write the report?
- Who attends site meetings with the builder and the council's tree officer?
- What do they do if work can't avoid an RPA?
Arboricultural consultants and tree surgeons are separate roles, although some firms do both. Check what is included in the quote.