We’ve had a huge rush in alleged subsidence cases with trees implicated lately.
These all seem to follow a similar pattern for us, the insurers receive the subsidence claim, an engineer makes an initial view and assessment of the damage, suspecting the tree is contributing to the problem. Soil samples are taken and sent to the lab, along with roots if they find any. The contracted by the insurer’s Arb guy turns up, guesses how big the tree is, marks it on a not to scale drawing leaving out all the details such as drains and says the tree is contributing and needs to be removed. At some point in the saga, there may be some level monitoring and perhaps attachment of tell tales, but it usually ends the same way with the tree being at fault and the chainsaws being dragged out by A N Other Tree contracting firm.
Sometimes though the homeowner, or even another interested party will ring us asking if this tree really is causing subsidence and can I give a second opinion.
Now unless the client has copies of any soil reports and level monitoring I won’t take their money, but if there is and I’ve had a look over it and there appears to be a wrong call or a large number of inaccuracies then I’ll take a look. Sometimes I’ll even do it for free, especially if it’s a case of “your trees going to make my house fall down” even though the only thing that’s moved is the poorly laid patio chucked on a bed of sand.
Now I’m going to dispel some Myths.
Bear with me because this one will cause a few arguments but, Trees don’t cause houses to subside. They can extract moisture on highly shrinkable soils that can cause movement but if a tree was present then that should have been designed around by the structural engineer and normally the arb report produced at the planning stage would have helped him make an informed decision.
Trees don’t break foundations or drains. Those things are impermeable dense objects and roots can’t grow through them, if they could we wouldn’t use root barriers/deflectors and let’s be honest, pot plants would be escaping left right and centre leaving trails of destruction and terracotta in their wake!
Poorly designed and installed foundations are normally the cause, but insurers don’t like to admit it. Why? Because it’s cheaper to remove a tree than put the job right properly or to chase after the individual who cocked up either the design or the installation in the first place.