Issues about trees are common in the context of disputes with neighbours. We are regularly asked to advise on problems such as tree roots causing damage or whether any action can be taken to reduce the height of a neighbour's tree, which is blocking the light into someone's home or causing concern about the structural integrity of their property.
Disputes regarding trees are common because some people want to maintain ultimate privacy, so they allow their trees to grow very tall and undertake very infrequent pollarding and maintenance. While this may suit one homeowner, the impact on neighbours can be significant and affect the quality of their enjoyment of their own property.
The law of nuisance can be helpful because the fundamental principle of common law nuisance is that a landowner is not allowed to do anything on their property, even if it is lawful, if it causes another party a nuisance. Roots and branches of a tree on someone else's land can cause a private nuisance if they cause physical damage to next door or a building or vegetation on that land or interfere unreasonably with the owner's enjoyment of their land.
Sometimes tree roots can cause direct damage to underground structures, for example, breaking drains or pushing up foundations and can also indirectly cause damage by affecting the water content of the soil, particularly if it is on a clay foundation.
When a tree is in full leaf, water is lost by it evaporating from its leaves, and it has to be replaced by water drawn by the tree from the soil by its roots. As it dehydrates, the soil shrinks and evaporation from the leaves naturally reduces after leaf fall. You can, therefore, have a cycle where, with greater winter rainfall, the amount of water in the soil increases, and as it rehydrates, the soil swells. This alternate shrinking and swelling can lead to the movement of structures on or in the soil and is often referred to as settlement or subsidence.
Tree roots can affect neighbouring land whether or not the roots encroach across the boundary into the neighbouring land. In severe cases, you may need to have your structures underpinned if they are affected by subsidence, the tree may need to be brought down completely, the top growth may have to be heavily reduced to reduce the evaporation of water from the leaves, or the roots may need to be pruned heavily to reduce the amount of water that they are taking up from the soil.
Complaints regarding tree branches are less likely to be classed as private nuisances unless they actually encroach on a boundary or cause a health and safety issue.
The leading case on damage to property caused by encroaching tree roots can be found in Delaware Mansions v. Westminster City Council in 2001. In that case, the House of Lords acknowledged that there isn't very much legislation or case law in this area, but the case itself laid out a test to be used when considering a tree root damage case. The relevant questions to ask are :
- whether there is a duty of care owed between neighbours with regard to trees,
- has the tree root caused the damage to the neighbouring property,
- was the harm reasonably foreseeable,
- was there any practical step that could have been taken to minimise or avoid the damage and
- whether or not there was a reasonable response to the damage?
The cases establish that the tree owner must do what is reasonable in all the circumstances to prevent or minimise the risk of interference with or damage to the property of the neighbour where they knew of the encroachment of the tree roots or branches or ought to have been aware of the trespass and there was a reasonably foreseeable risk of damage to the property or the enjoyment of it as a result of the trespass.
Delaware also established that a property owner can be held liable for the nuisance caused to its neighbour's land or property, even if this occurred before they bought their land. An owner or an occupier of land continues a nuisance if, with knowledge or presumed knowledge of its existence, they failed to take reasonable means to bring it to an end, having had a reasonable time to do so.
Questions of causation can also be tricky in these cases. Someone would have to prove that the tree roots caused the damage. Other factors can sometimes be relevant, including faulty construction of the original property, settlement into the area and more damage.
There must also be a reasonably foreseeable risk of damage to the neighbouring property or its enjoyment from the effect of the tree roots. In effect, the tree owner must know or ought to have known of the presence of the roots and the risk they posed, and that risk must be one that a reasonable person in the tree owner's position would have regarded as a real risk, not just a vague possibility. The more foreseeable a risk is, the more important it is to take sufficient precautions. Homeowners need to take care if the trees could easily have been pruned to avoid subsidence, but they have failed to take steps to do so, especially when they have been asked to do so by their neighbour.
Tree owners are not expected to remove all trees on suspicion that a small number of them might cause damage to neighbouring properties, but it would be prudent to ask an arboriculturalist to inspect once every couple of years so that you can show that you have appreciated that there might be a risk and have taken sufficient safeguarding measures.
