It’s nice to have trees around our homes. A tree can add many things to houses; shade, character, birds and somewhere for the kids to play.
But what happens when the trees rise from centuries of servitude, and come looking for revenge?
Some trees are spiteful buggers and can damage our homes in a number of ways.
- They can fall on your home. Less damaging than an aeroplane, more damaging than rain.
- They can drop leaves into gutters, catch fire and burn your home to ashes.
- They can tear your house apart like a sea monster wringing the life out of a sailing ship.
Well maybe not exactly like a sea monster, but they can put some serious stresses into a building. Not so much like a tentacle, but by sucking the water out of the ground through their roots.
Oh, and apparently trees can break dams and flood your home, like the ents in Lord of the Rings. It was on TV so it must be true.
How does this happen?
We build our homes on many types of soil. Soil, like many other things, expands when wet and shrinks when dry. Trees drink water out of the ground through their roots. So a tree can dry out the ground under one part of your home, while another remains wet. This can create a low spot under part of your house, and that part of the house ‘falls into’ the low spot. This is when you can see cracks appear.
Of course nothing in life is really this simple, some plants are more damaging than others, and some soil types expand more than other types when they get wet.
However, as a simple guide:
- Thirsty plants suck out more moisture and cause more damage than say a cactus.
- Shrubs and trees with deep roots cause more problems than those with shallow roots.
- The bigger the plant, the more water they need.
What can I do?
The first step is to avoid damaging plants. Plants to avoid include melaleucas and eucalypts (thirsty and big). Plants that are OK include rhododendrons and azaleas (shallow roots). Eucalyptus are among the worst because they are native, can grow to a large size and they are almost everywhere. A good nursery or landscape designer are great places for information on which plant to choose.
Keep plants away from the house. An old trick is to put a footpath around the entire house, to keep the ground adjacent to the house at a consistent level of moisture.
Small plants and shrubs are better than larger shrubs and trees. So plant some flowers and small shrubs near the house, not a blue gum. In fact never plant a blue gum anywhere near your home.
Keep trees away from the house! How far away? Advice from engineers, plant experts and the CSIRO is consistent: 1 to 1.5 times the height of the fully grown tree, is the distance to keep it away from the house. So a nice gum tree which eventually grows to 30m tall, (yes, it’s a small one) should be planted around 45 m from the building. So if a tree is close enough to fall on your house, it’s close enough to cause foundation damage from drying the soil.
If you are going to have some plants around the house, either try to prevent excessive or irregular watering or choose plants which are drought tolerant and don’t need watering.
The eagle eyed among you have picked up I haven’t gone into soil types. That’s for another day.