Vertical displacement Vertical displacement is a difference in height between adjoining concrete slabs or sidewalk flags. The uneven elevation creates an irregular walking surface.
Vertical displacement can result from settlement, tree root growth, frost movement, or deterioration of the supporting soil beneath the pavement. Even relatively small height differences may become trip hazards for pedestrians. Repair methods typically focus on correcting the underlying cause before restoring a level sidewalk surface.
Frequently Asked Questions About Vertical displacement
What is vertical displacement?
A difference in height between adjoining sidewalk flags, creating an uneven walking surface.
What causes it?
Settlement, tree root growth beneath one slab, frost movement, or erosion of the supporting soil.
How much displacement is a problem?
In NYC, a half inch or more between adjacent flags generally meets the trip hazard threshold, and smaller differences can still cause falls in poor lighting.
How is it repaired properly?
By addressing the underlying cause, such as roots or a failed base, before replacing the flag. Otherwise the displacement returns.