Tree roots are often blamed when buildings sustain damage. The frequent need for factual and expert evidence relating to structural damage in such matters means that tree roots are a topic familiar to many construction lawyers. They are also relevant to those in the building and property professions. For example, if your client buys a property on which trees are growing that may be causing damage, by 'continuing' the problems caused by those trees, your client may become liable for the damage. Since a decision of the Court of Appeal last year, it is also possible that, if your client buys a property that has already suffered tree root damage, they may be able to recover for it from those responsible for the offending tree.
The technical arguments usually rehearsed in court are, in short, that where there is a shrinkable clay soil and trees extract moisture on a seasonal cycle, the soil may expand and contract, which in turn may cause building movement.
Between them, structural engineers and arboriculturalists generally give expert evidence about a wide range of tests including plasticity and desiccation of the soil, identification of tree roots, level and crack movement monitoring, and the type and extent of damage caused.
The legal basis of tree root claims is usually nuisance. This is not nuisance in the usual sense, but a specific branch of the law of tort, another branch of which is negligence. A tree root claim founded on negligence would face the difficulty that damage to buildings is generally held to be economic loss which is not usually recoverable in a negligence action. In contrast, the tort of nuisance specifically relates to the interference with occupation and enjoyment of land; indeed the claimant has to have an interest in the affected land in order to bring an action. Many property-related claims are brought in nuisance, for example the claim in Hunter v Canary Wharf concerning interference with TV reception. As well as proving their interest in the land, a tree root claimant has to show encroachment by the defendant's tree roots, and prove damage caused to their property by the roots.
The defendant is the person who has control over the trees, and can take effective steps to curtail them. That person is effectively the wrongdoer, even if their wrongdoing is simply inaction. In addition to a common law duty not to cause nuisance, some defendants have statutory duties. A local highways authority has particular duties relating to trees growing on the highway, and even more onerous duties if they planted those trees themselves.
Someone who buys land with trees on it that are already causing a nuisance may become liable for the damage. According to the judgment in Roswell v Prior (1701), the problem falls at the door of the new owner because it was 'his fault to contract for an interest in land on which there was a nuisance'. The court will look at whether the new owner knew or should have known about the problem. If so, he may be liable.
There are signs that nuisance may be expanding its scope. Last year the Court of Appeal heard the case of Delaware Mansions v the City of Westminster . Various blocks of flats were sold in 1990 after they had suffered damage caused by the roots of a plane tree for which Westminster was responsible. Westminster argued that as the damage had been caused before the claimants owned the flats, the claimants could not recover for the damage; it had not been caused to the claimants' property.
Presumably the vendors could not recover because they no longer had an interest in the land. The Court disagreed with Westminster, deciding that there was a continuing nuisance which gave rise to a continuing cause of action, and the claimant recovered. In the same judgment, the Court of Appeal decided that the actual and relevant damage was the cost of remedial work, thereby effectively awarding the claimant their economic loss.
This case seems to have opened up new opportunities for those who acquire properties affected by tree roots, while necessarily increasing the potential liabilities of those responsible for trees.