A Technical Report from The Bartlett Tree Research Laboratories 244
Tree roots grow underneath sidewalk pavement when there is oxygen, water and space for them to grow. Roots are very small when they start growing under pavement but then increase in diameter as the tree grows resulting in lifting or cracking of the pavement. When pavement lifting is excessive, a pedestrian tripping hazard is created. It then becomes a challenge to preserve the tree while continuing to allow pedestrian use of the sidewalk.