Partial-Depth Repair The purpose of partial-depth patching is to restore localized areas of deterioration that do not extend through the slab. The most common problem is spalling, but partial-depth repair can also be used for small areas with severe scaling. Partial-depth patches are acceptable for most surface problems at joints, cracks, and midslab locations that are within the upper one-third of the slab. Partial-depth patches are usually very small. Each patch usually covers an area less than about 10 square feet. They are often only 2–3 inches deep. Spalling is typically a random and localized problem. Surface spalls create a rough ride and can accelerate development of further problems. Partial-depth patches replace unsound concrete to restore rideability and deter further deterioration. They also provide proper edges for resealing joints and cracks.