What is the maximum layer thickness when using FDP?

Answer: B — 3 inches.

When performing a full-depth patch, each lift of patch material should be placed no thicker than three inches. This limit ensures the asphalt can be compacted properly with standard rollers and equipment, creating a dense, well-bonded repair that matches the surrounding pavement. If more depth is needed, the patch is built up in successive lifts, each limited to three inches and typically reinforced with a tack coat between lifts to promote adhesion. Thicker lifts are hard to compact adequately, which can leave air voids, weak joints, and settlement problems, making the patch prone to cracking and failure. Therefore, the maximum layer thickness is three inches.