How to stop tree roots spreading and encroaching

Are you concerned about encroaching tree roots from a neighbour’s property? Or, how to stop tree roots from spreading at your own property and causing damage? Trees are undeniably important, but their roots are powerful and can cause damage to structures. When taking action, understanding how far the roots of a tree species can spread is an important first step. Once understood, tree root protection measures can be considered that can mitigate tree root encroachment.

Reassuringly, there are effective methods that can be used to prevent the spread of tree roots. With the correct approach employed for the situation, you can stop the spread of tree roots and safeguard against potential property damage. We'll explore the methods used, but first consider the root span of specific tree species.

How far do tree roots spread?

Scoping the extent of tree root spread is a complex matter. It's one to which arboriculturists dedicate a significant amount of time. Tree roots can travel long distances, as indicated below. These are perhaps extremes, as the lengths recoded here, illustrate the longest root distances for each of species. In many cases, tree roots will not travel this far, so seeking professional arboricultural advice for your specific situation is always wise.

The root spread of common UK Tree Species
The chart below illustrates the longest root spread you can expect for common UK species.
(Find sources used for tree root length at the foot of the page).

This illustrates the importance of allowing enough space for trees to grow. Trees that are long established can, of course, cause problems; however, tree planting allows for consideration of future issues.

Planting fruit trees is particularly common in the UK. When selecting varieties of apple, pear, and cherry, consider the root spread of the species.

The chart above lists the longest root span to expect for fruits commonly planted in the UK. The green portion of each column represents the 'typical' minimum safe planting distance from property of that fruit variety.

N.B. It's important to note that there are a number of subspecies for each fruit variety and therefore actual numbers will vary. Research the specific plant species before planting.

How do you stop tree roots from spreading?

If you’ve ever seen tree roots spreading under driveways, lifting pavers, and affecting sewer lines, then you will know that prevention is fundamental. However, resolving the issue with existing trees will require a different approach to new planting. Whilst it may be more challenging, it is not impossible.

In both scenarios, using root barriers is often the best solution. What is essential is to obtain the best advice; root barrier design will be required in both scenarios.

What is a tree root protection area?

The term Tree Root Protection Area (RPA) directly relates to BS 5837:2012 Trees in relation to construction. This British standard examines tree root protection to determine the available land areas for development, allowing for a construction exclusion zone so that the long-term retention of trees is achieved.  

Typically, the RPA is cited when looking at tree root protection, which in its simplest form equates to 12 x tree stem diameter at 1.5m above ground, but this may not be relevant in many situations. An alternative approach is to consider tree root protection by following NJUG Guidelines for the initiation and maintenance of utility apparatus in proximity to trees.

Although not suitable for all situations, this guidance categorises tree protection zones as follows:

Prohibited zone = 1m from the trunk, no excavations of any kind

Precautionary zone = beneath the canopy or branch spread = hand excavations or with specialist air spade where exposed roots must be protected. The ability to install root barriers in this area would be limited. Some tree root removal may be acceptable to deal with contact heave, for example, but this would be subject to the tree's TPO status and the area's conservation area status, as permission or notification would be needed.

Permitted zone = outside the precautionary zone. Excavation works may be undertaken to install root barriers, but a precautionary approach must be adopted, with mechanical plant limited and any exposed roots protected. When working near trees the Precautionary zone should be fenced off to avoid storing or traversing the area.

In conclusion, various methods and practices are employed to determine tree root protection areas, and it's important that they are used appropriately. As such, professional advice should always be sought.

Tree root encroachment on property

While trees often overhang property boundaries, people often forget that tree roots also encroach into neighbouring land. However, tree root encroachment can become a complicated and litigious issue, so it is prudent to prevent tree roots from spreading to neighbouring land.

Preventing tree roots from encroaching on a neighbour’s property

When planting close to a boundary, installing tree root barrier is becoming increasingly important for the reason cited. Installing root barriers will cost much less than fixing damage caused by tree encroachment, especially when considering legal costs.

Installing a root barrier when planting new trees has become more common, when tree planting in an urban area its essential.  and  The depth will depend on the soil type and the potential rooting depth of the chosen tree species whose tree root you are looking to block.

A root barrier positioned on boundary line, that extends far enough away from the rooting potential of the chosen tree species, is most desirable. Alternatively, create a rooting zone around the tree or trees being planted. However, as trees need sufficient soil volume to thrive, ensure you position the root barrier to provide enough soil for the tree to establish itself.

How to block tree roots from a neighbour’s property

Tree roots encroaching from neighbouring properties can pose significant challenges. When root damage begins to cause issues, understanding how to effectively block them becomes a priority. The installation of root barriers can provide a viable solution. However, approach this solution with careful consideration of the location in relation to root protection areas, ensuring compliance with tree protection orders and conservation area regulations.

Consulting with an arboricultural expert is typically advisable to ensure that the chosen solution aligns with legal requirements and environmental best practices.

Sources: 'Trees: Their Natural History' by Peter Thomas, 'Urban Tree Root Research in the UK: A Review" by K. J. Dobson and K. L. Moffat (1993), 'Principles of Tree Hazard Assessment and Management' by David Lonsdale

'Tree Root Systems and Their Mycorrhizas" by Sally E. Smith and David J. Read, 'Tree Root Damage to Buildings" by P. G. Biddle, 'Principles of Tree Hazard Assessment and Management' by David Lonsdale