What’s an Arboricultural Survey and why do I need one?

At SWJ Consulting, we often work with clients in the early stages of development who need clarity on the condition of their site before progressing with design work. Three of the most common types of surveys commissioned during this stage are Site Surveys, Arboricultural Surveys, and Topographical Surveys (read about the difference between a site investigation and topographical survey). While they are all surveys, site surveys typically deal with the soil/ground conditions, an arboricultural survey is focused on the trees, and a topographical survey looks at the features of the site above ground, so the purpose and outcomes are quite different. Understanding when to use each can be critical to the success of your project.

An Arboricultural Survey

An Arboricultural Survey, also known as a Tree Survey, is a specialist assessment carried out by a qualified arboriculturist to record the condition, species, age, health, and root protection areas (RPAs) of existing trees on or near a site.

This type of survey is often required by local planning authorities to ensure that development proposals take proper account of trees — particularly those protected by Tree Preservation Orders (TPOs) or located in conservation areas.

The key outputs of the survey typically include:

  • Tree location and species
  • Tree dimensions (height, diameter, canopy spread)
  • Tree condition and life expectancy
  • Recommendations for retention, removal, or management
  • Root Protection Areas (RPAs)
  • Impact assessments for proposed works

A Topographical Survey

A Topographical Survey is a detailed mapping of the site’s physical features and levels. It provides a 2D or 3D representation of everything visible on the ground — such as buildings, roads, fences, utilities, boundaries, and ground levels. This also indicates where existing services and utilities will be.

While a topographical survey may indicate where a tree is located, it does not provide the in-depth health or root system analysis needed to inform planning or foundation design decisions.

Survey Type Focus Conducted By Purpose
Site Survey Soil sampling, groundwater conditions, and contaminants geologists, geotechnical engineers, environmental consultants Physical and chemical properties, suitability for the proposed use
Arboricultural Trees and root zones Arboriculturist Tree health, planning compliance, and RPA impact
Topographical Ground levels and site features Land Surveyor Site layout and design coordination

When would you need an Arboricultural Survey?

Clients might commission a tree survey for several reasons:

  • Planning Requirements: Local authorities may request an Arboricultural Impact Assessment (AIA) as part of a planning application.
  • Risk Management: Assessing whether any trees pose a risk to buildings, people, or utilities.
  • Foundation Design: Understanding the impact of tree roots on soil moisture and shrink/swell potential, particularly in clay soils.
  • Preservation & Landscaping: Identifying which trees should be retained and protected during construction.

A tree’s impact on foundation design

One of the most critical ways tree surveys inform our work at SWJ Consulting is through foundation design.

Certain tree species have high water demand and extensive root systems that can affect the moisture content in the soil. In shrinkable clay soils, this can lead to heave (rising) or subsidence (falling), movement of the soil, which requires careful engineering solutions.

For example, if a large oak tree is located close to a proposed extension. The Arboricultural Survey may identify a significant RPA (root protection area) overlapping the proposed site. Based on this information, we may then recommend a piled foundation with suspended floors to avoid or minimise potential root damage and mitigate any future subsidence risk.

It’s not just the trees that are still in existence that we need to consider. The effect that removing trees to clear a site also needs to be considered. If a proposed site had a group of fast-growing conifers removed to make way for the development, the Arboricultural Survey would flag the risk of soil heave as moisture levels recover in the ground, so we would need to design foundations accordingly with heave protection measures.

As always, collaboration is key

At SWJ Consulting, we work with specialists such as arboriculturists, surveyors, geotechnical engineers, and environmental consultants as well as architects and contractors to ensure that both the structural and environmental aspects of a site are carefully considered. Where needed, commissioning and using tree survey data early in the design process will help mitigate risks and anticipate planning issues where trees might be concerned. This will reduce the potential for delays and additional costs further down the line.

Need advice on tree-related constraints?

If you’re planning a project on a tree-populated site — or simply want to future-proof your development, give us a call.  We can advise on the right surveys to commission and then design the more efficient foundation solutions for your project.

Get in touch on Witney (01993 225085) or Southampton (02381 920656) or email mail@swjconsulting.co.uk