What is the minimum depth of cover under a driveway if the frost line is 2 1/2 ft?

The correct answer indicates that the minimum depth of cover under a driveway should be 3 ½ feet when considering a frost line of 2 ½ feet. This depth is chosen to ensure that any piping or underground systems are insulated against the effects of frost at the surface.

When the frost line is identified at a certain depth, it signifies the point below which the ground remains unfrozen during winter months. To prevent frost heave, which can damage buried pipes or utilities, the minimum depth of cover needs to exceed the frost line by an appropriate margin. In this case, covering the pipes by an additional foot is a common practice to provide extra protection against freeze and thaw cycles.

By specifying a minimum of 3 ½ feet, this depth accounts for the frost line depth while allowing for variations in ground temperature and conditions, thereby ensuring the integrity of the underground systems throughout seasonal changes.