Trees can cause major damage to your home, garden and boundary walls. Without care and control, they may cost you a lot of money and no small amount of effort to fix.
Ensure also that shrubs are not planted too close to masonry walls. The building regulations specify a minimum distance of 1,2 m for normal soils and 1,5 m if you have clayey soil.
Roots can also grow beneath your foundation and lift the house or they can leach water from the ground during dry spells and sink or settle the house unevenly.
Trees cause the soil to dry out and, in the case of clay soils, to shrink.
Any subsequent watering or extended rain periods will cause the clay to swell. In this way, trees and large shrubs can cause movement on clay soils resulting in damage to your home and walls.
The amount of movement depends on the percentage of clay content, the depth and extent of the root system of the tree and the efficiency of the tree to extract moisture from the soil.
When underground sewer and water pipes develop small leaks, roots will quickly take advantage of those leaks. Before you realise it you have a blocked sewer line and pools of water and sewage in your yard.
Trees not to plant
All trees should be regarded as a potential source of damage. The following varieties are, however, particularly prone to causing damage:
- All eucalyptus varieties
- Lombardy (Free State) poplars
- London planes
- Willows of any type
Also, make sure to keep an eye out for signs of trouble. Clues that roots have clogged pipes include slow-flowing drains, as well as gurgling from toilet bowls. If you suspect a problem, sewer cleaning companies can clear root-clogged sewers.
Depending on the amount of clay in your soil, plant trees as recommended by SANS10400-H Annex-D: Tree Damage to Walls & Foundations. Find out what the expected mature height of the tree should be and multiply by the factor below.
- Slight clay content – height x .75
- Moderate clay content – height x 1
- High clay content – height x 1.5
This will provide you with the distance you should plant the tree from walls, your home’s foundation and your sewers.
Above ground, trees can cause other problems for homes when they get damaged by severe storms, wind, or lightning. This can send trees or branches crashing down or through the roof of your house.
Dead or dying trees are particularly problematic because branches are already brittle. You can tell a tree is dead or dying if:
- The tree doesn’t leaf out in spring, or it produces small, discoloured leaves.
- Splits appear in trunks and branches.
- Trunks become hollow.
- Fungi such as mushrooms grow on branches or root flares.
- Trees tilt more than 15 degrees from the vertical.
It’s sometimes hard to predict all the ways a tree can wreck your property. Look for obvious tree defects such as holes on trunks and dead branches.
You should also prune trees every two years to raise canopies and remove dead branches. You should trim tree limbs away from your roof and your neighbour’s property.
If you’ve got a tree that’s causing problems for your home, you have some options:
- Remove the tree.
- Move the tree, which depends on age and size. Younger trees are more likely to survive the move than older trees, which could cost tens of thousands to relocate.
- Control the roots by either pruning them, blocking them with plastic barriers or applying a growth inhibitor. This will redirect the tree’s energy toward fighting disease and pests, rather than growing roots and branches.
You should consider the effects of the removal of trees on clay sites. It is important to realise that removal might result in large swelling movements as the dry clay absorbs water. This will particularly have an effect where trees have lowered the water table over a period of time.
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