Trees and buildings

One of the main causes of structural movement is clay related subsidence. As indicated above, one of the contributing factors in this type of subsidence, is the presence of trees/hedges close to buildings. The roots suck up large volumes of water, thereby drying out the clay sub-soil, causing it to shrink in volume. The amount of water sucked up by the roots will depend on the type of trees/hedges, their age/size and proximity to the building. Generally broad leaved deciduous trees suck up more water than coniferous trees. Oak, Poplar and Willow trees are particularly thirsty. Young trees/hedges will require less water than older more mature trees/hedges. However, even small trees/hedges, if not regularly pruned/managed, will eventually grow and could cause future problems. The proximity of the tree/hedge to the building will determine whether or not the roots are likely to be within influencing distance of the buildings foundations. As a general rule, the tree/hedge roots will spread a horizontal distance of approximately one and a half times the vertical height of the tree/hedge. Apart from contributing to subsidence in clay sub-soils, trees/hedges can also reduce daylight entering a building, while full or partial collapse of large trees in high winds can cause structural damage. Finally tree/hedge roots can interfere with drainage pipes and other underground services. Problems often occur where trees/hedges growing on neighbouring land are suspected of causing damage. Consultation with the adjoining owner/occupant will be essential in order to agree a strategy. Once alerted of the possible risks posed by trees/hedges growing on their land, failure of the land owner to act in a reasonable and timely manner, could result in their being liable for any damage later caused by their inaction (under the law of private nuisance).

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