There is no doubt that trees are almost always an asset to a property. There is nothing sadder than watching healthy mature trees being removed to make way for a new housing development when, with a little forethought and careful planning, many could have been retained.
On the other hand, however, trees do have the potential to cause serious damage to property and there are times when extensive pruning, if not complete removal, of a tree is warranted.
If left unchecked, trees can cause structural damage to buildings, not just due to falling or overhanging branches but also due to roots sucking moisture out of the ground. As a tree grows, its water consumption increases.
As the roots spread towards a building they continue to use up available groundwater. This is mainly an issue for homes built on unstable clay soils. Reducing the moisture levels in clay causes it to shrink. This means that the ground no longer provides adequate support for any structure built over it, which can result in significant cracking.
You are most likely to notice this cracking along the underside of eaves, around window frames and other parts of the brickwork. You may also notice that doors are starting to stick.
The key to avoiding this damage is stabilisation of moisture levels around the house. This means ensuring you have good drainage, avoiding over-watering around the house and making sure that trees near the house are given additional water in the drier months.
Also make sure any plumbing leaks are promptly repaired. Ideally you should ensure that trees are planted well away from any structure, but if your problem is with an existing tree then you will need to find a way to manage the problem.
Removing the tree itself will not necessarily be the solution as this will result in an overall increase in moisture levels causing expansion of the soil, which can also result in structural damage.
Underpinning a home that has been damaged by unstable soils may be your best bet. You will need to engage an expert to advise you on what interventions are required.
You are likely to need new concrete piers in the problem areas, so the assistance of an experienced structural engineer is essential. The CSIRO produces a booklet entitled Foundation Maintenance And Footing Performance: A Homeowner’s Guide which is a good place to start.