Why arboricultural surveys play a key role in planning applications

Arboricultural surveys are designed to protect healthy trees from being lost due to development, and they calculate how to mitigate risk while protecting the trees. Arboricultural surveys are carried out for other reasons than just planning applications. While trees provide many environmental benefits, they can present risks to the safety of people or buildings, so surveys are undertaken to assess any dangers posed by trees. This article answers common questions about arboricultural surveys and explains the survey process.

What is an arboricultural survey?

Also known as a tree survey, an arboricultural survey is a technical report carried out by a suitable environmental consultancy that has extensive experience working on tree inspections. It looks at trees and shrubs in the designated area to assess how potential development plans would affect them, while also assessing threats from trees to buildings or any health and safety risk. They are especially relevant when considering old trees or those damaged by disease, storms or pests. An arboricultural consultant will also inspect to see if tree roots have caused any subsidence under buildings.

When is an arboricultural survey needed?

If you’re considering development work, whether it’s a small extension or a sizable new build, if there are trees on or close to the site you will probably need a tree survey to accompany your planning application. They are relevant to developers by informing them of any issues with trees on a site and nearby trees as well as to site or tree owners, landscape designers or project managers.

UK local planning authorities are required to check the impact of any planning application on trees and vegetation. Trees are protected under the Town and Country Planning Act 1990 and the Planning (Listed Buildings and Conservation Areas) Act 1990, particularly through the use of conservation areas and Tree Preservation Orders (TPOs).

Local planning authorities require tree surveys to be carried out to the British Standard BS5837, which will:

  • Assess the impact of a development scheme on trees on or near the site.
  • Consider how the future growth of trees on the site may affect any development.
  • Recommend which trees should be retained to comply with guidelines.
  • Identify trees that should be preserved on the site.
  • Identify any risks from trees on the site.

Tree Preservation Orders (TPOs)

A TPO designation protects a tree from being damaged or cut down without written consent from the local planning authority (LPA).  An arboricultural survey will take any TPOs into account to prevent any breach: anyone found breaching a TPO can be liable to a fine of up to £20,000.

How often should an arboricultural survey be carried out?

This depends on the site in question; generally, trees should be inspected on a regular basis, possibly every two years. However, a tree that’s showing early signs of disease or damage would need more frequent attention.

How much does an arboricultural survey cost?

Costs will vary according to the number of trees on the site.

A footpath through woodland.

The tree survey process:

BS5837 tree surveys and tree constraint plans

The BS5837 survey is a stage 1 survey that involves drawing up a tree constraints plan required for most planning applications involving trees to assess whether any need protection. A tree surveyor assesses all trees within your site boundary and nearby trees in relation to your development scheme. If they find that trees will be impacted, they will work out ways of adjusting the project to safeguard the relevant trees. If this is not possible, a grading system can be brought into play to rate the quality, life expectancy and condition of each tree which enables decisions about relocating or removing trees. The aim is to provide a reasoned balance of tree removal and retention of individual trees, with justification provided for removing low-quality trees.

Qualified tree inspectors assess tree impact both above and below ground, using high-tech equipment to produce a tree constraints plan drawing. All trees on and adjacent to the site will have a BS5837 retention category, detailing the tree’s size, health, estimated lifespan and contribution to the area. The categories range from category A for the most important trees, to category C, and of course, high-quality trees will present more of a constraint to development.

Canopy and root protection

Part of a tree survey involves considering how best to protect the tree canopy and roots. While the canopy can usually be safeguarded by simply erecting fencing around the tree, the root protection area (RPA) – the rooting environment the tree needs to survive – can be more complicated. The RPA is important as roots need to respire; oxygen and gaseous exchange must happen for them to survive, and they are sensitive to any compaction of the earth around them. Soil moisture levels will be investigated to check that they are at an acceptable level.

The equation to work out the RPA involves taking the diameter of the tree stem at 1.5m above ground level and multiplying it by 12 to calculate the radius of the area that needs to be protected as a circle surrounding the tree.

A tree surveyor’s theodolite.

Arboricultural Impact Assessment

This is a stage 2 survey that investigates further into how a potential development site would impact trees. It’s required when a local planning authority wants to see how a scheme proposes to retain high-quality trees while achieving the development aims. This assessment covers the RPA protection strategy, above-ground issues such as on-site transport and storage to protect trees, and the site’s potential for future problems such as having to remove trees due to issues caused by shading or leaf litter.

Arboricultural method statement and tree protection plan

Sometimes a local planning authority will request a drawing and statement to show how good quality trees will be retained and protected on your site. An Arboricultural Impact Assessment and a tree protection drawing plan deal with the methods for protecting high-quality trees. The method statement and tree protection drawing will be created on a plan giving detailed information about level changes, utilities infrastructure, surface treatments and the building footprint.

Most will cover details about the following:  

  • Tree retentions and removals.
  • A schedule of tree works.
  • Surface treatment and level changes near trees.
  • Storage and transport of materials.
  • Siting of protective barrier fencing.
  • Tree planting and landscaping.
  • Engineering solutions, for example, excavating near a RPA.
  • Arboricultural supervision of the site required by the LPA.

Arboricultural supervisions and site monitoring

As a Stage 3 element of gaining planning permission, sometimes the LPA will stipulate that an arboricultural surveyor must monitor trees on a site to ensure that the protection plan is being adhered to: this is often dependent on the complexity of the development.

Regular tree surveys will assess the risk of storm damage on individual trees.

Other types of tree survey

Mortgage tree reports and health and safety tree surveys

A mortgage tree report may be requested by your insurer or mortgage provider to ensure there’s no risk from trees. This survey provides detailed information by inspecting trees near a property for condition and safety to reduce risks to an acceptable level, and considers potential issues such as trees with a Tree Preservation Order or trees sited in a designated conservation area. There is a correct protocol to observe, and these reports may be needed if you are a tree owner or are thinking of buying land with trees and need to assess how these protocols could affect you.

A health and safety tree survey aims to reduce the risk of damage to people or buildings by assessing potential hazards such as dangerous branches or decayed trees that might fall in high winds. Qualified tree inspectors may use tree motion sensors to monitor suspect trees. The arboricultural report will grade trees to determine their life expectancy and check them for fungal decay and other diseases that could cause tree failure.  

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