Although relatively rare, tree roots have the potential to damage underground structures such as foundations and underground services. Such effects can be the result of either direct or indirect rooting damage.

Direct rooting damage occurs when roots contact or penetrate a structure causing harm. This may happen several ways;

• * When roots increase in size they apply pressure directly on underground structures. As this type of damage is usually caused by the tree's primary structural roots, it only tends to occurs when trees are situated close to structures. Guidance in the British Standard BS 5837:2012 (Trees in relation to design, demolition, and construction – Recommendations) suggests that risks are more significant when trees are with approximately 3m of a structure.
• * The movement of a tree's primary roots in windy conditions can also disturbs adjacent structures. Again trees usually need to be within a few meters of the structure for this type of damage to occur.
• * Tree roots can penetrate a structure, such as a wall or drain, and then cause damage as they increase in diameter, or cause an obstruction within, as commonly happens with drains. It should be noted that root growth is not able to penetrate adequately installed structures, and only exploits exiting holes and cracks. In many cases, such existing damage is not tree related, although it can be caused by the other scenarios detailed in this guide.

Indirect rooting damage occurs when a tree's moisture demands shrink (causing subsidence) or swell (causing heave) the surrounding soil volume, damaging structures within it. Such effects can impact structures at distances of over 30m from the causal tree, although in most cases the distance is significantly less. For a tree to cause such damage the soil must contain clay or peat deposits. It should also be noted that subsidence and heave have many causes of which tree roots are only one.

• * Root induced subsidence most commonly causes damage to foundations and walls during hot dry weather, when trees remove more water from the surrounding soil. Ordinarily, damage is typified by diagonal cracks in walls that are in reasonably close proximity to trees. The damage often first appears at the corners of buildings, around door/window openings, and where extensions and primary buildings adjoin. Cracks can often become less severe, or even close completely, at the onset of wetter weather or winter.
• * Root induced heave, the most uncommon form of rooting damage, usually occurs when a significant tree is removed and a structure is installed immediately afterwards. As the ground slowly re-hydrates following tree removal, it swells, lifting and damaging structures upon it. The damage may appear like that caused by subsidence, as described above, but is much less likely to coincide with extremes of weather.

If you feel you may have tree rooting related issues, please contact us for a free initial consultation.