The presence of vegetation, particularly fast-growing trees near compound walls, can lead to cracks in walls because of the expansive action of roots growing beneath the foundation. Tree roots typically spread horizontally, reaching the height of the tree above the ground. When trees are situated close to a wall, this scenario should raise concerns. Sometimes, plants take root and grow in wall cracks due to seeds carried in bird droppings. If these plants aren't removed promptly, they can worsen over time and cause significant wall cracking.
When the soil beneath a building's foundation consists of shrinkable clay, cracks in walls and floors can occur for two main reasons. Firstly, the dehydrating action of growing roots on the soil may cause it to shrink, leading to foundation settlement. Secondly, there can be upward pressure on parts of the building when old trees are removed, and the soil, previously dehydrated by the roots, swells upon receiving moisture from sources like rain.
Here are some general guidelines to prevent cracks caused by vegetation:
Avoid letting trees grow too near buildings, compound-walls, or garden walls, especially if the soil beneath the foundation is prone to shrinking, like sandy or clay soil. If tree saplings begin growing in cracks in walls, promptly remove them.
If mature trees are nearby and aren't causing issues, it's best not to disturb them, particularly if the soil under the foundation is prone to shrinkage.
If vegetation, including trees, is cleared from a site planned for new construction, and the soil is shrinkable clay, refrain from starting construction until the soil has expanded after absorbing moisture and stabilized.
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