You cannot rule out, though, that human error could be to blame due to incorrect foundation depth, steel reinforcing positioning or lack of, incorrect foundation design and strength or just generally taking shortcuts during construction. Large trees have been known to affect external walls of dwellings up to twice their height. So, if the tree is 30m high, then the roots could travel up to 60m away underground.
Foundation and Cracking Problems
Tree roots basically provide two functions: giving the tree stability so it’s able to stay upright and to provide the tree with a food source, one being water. As the tree grows bigger and higher, the root system has to grow as well, travelling further away in search of food. If there are, or have been, drainage issues to the property, then the roots will hone in to this area as a good food source.
Rectifying Drainage Problems
If and when the drainage problem is rectified, the tree roots remain, taking all the moisture out of the soil and causing the clay to shrink. The higher the clay content, the more shrinking will occur. The moisture content of the ground in and around the dwelling should remain the same from winter to summer as this ensures a stable foundation.
Install a Root Barrier System
If large trees are present around the property and you would like to protect the structure from the root system, a root barrier system can be installed under the ground between the dwelling and tree about 1.5 meters from the dwelling. A root barrier is a 100 – 200mm trench about two to three metres deep that is full of concrete with a membrane at one side. The trench should be long enough so the tree roots cannot go around the trench near dwelling.
Do you need an Inspection?
If movement is apparent to a section of the dwelling and is increasing in size, then it is advised to have the area inspected. A Buy-Wise Inspection Services Inspector can compile a report on all the contributing factors in regards to the movement, and advise on the best course of action.
Soil Test or
The next course of action may be obtaining a soil test (Geotechnical Report) and an Engineers Report to determine if the best solution is underpinning the existing foundations. On average, the soil test and engineers report could cost $1500 – $3000, depending on the circumstance.
The cost to underpin foundations can be $5,000 – $40,000 +, so it is important to gather all the correct information to determine if this course of action is required, or if other, cheaper methods could be adopted with the same result.