9 March 2022

How many times, while walking or cycling, have you been bothered by cracks in the asphalt and lifted paving bricks? Or even worse, have fallen over it? Year after year cities spend a lot of money on pavement restoration to prevent damage claims of residents. There is always a lot of speculation as to which came first; the root or the crack.

Pavement damage caused by tree roots can be prevented
As tree enthusiasts we would like to believe the crack was there first and that the civil specialists are the ones to blame. Unfortunately, the story is more complex and a combination of various design aspects (both technical and aesthetic), the execution of the work and local conditions. But with the correct implementation (design and realisation) damage can be prevented.

Unfortunately, when it comes to public spaces, compromises are often made due to budget or conflicting requirements. These conflicting requirements are often at the root of the problem and make it almost impossible to rule out heaved pavements. A lot of studies have been done on the relationship between tree roots and damaged pavements. These studies often relate to a specific location or tree species.

Trees in structural soil
Research also shows that tree roots in structural soil branch out more easily; resulting in more and smaller roots. But as soon as these smaller roots grow bigger than the pore space between the rocks, structural soil root heave is inevitable. Structural soil will only postpone root heave.

General conclusion: two causes of root heave
After evaluating these research reports, the general conclusion is mainly determined by two important facets. First of all, bigger roots cause more damage (roots grow bigger and bigger every year). Secondly, the damage is greatest when roots grow higher in profile. That is why most damage is caused by big roots growing close to the surface.