Expansion joints are designed to prevent your masonry from cracking by allowing your building to shift and flex with ground movement and temperature changes. If your expansion joint’s caulk is damaged, it can’t do its job. To replace it, fist the old caulk must be cut out. The sides of the joint where the old caulk was must be prepared so that new sealant will adhere properly. A neoprene “backer rod” will be inserted into the joint to act as filler and give your new sealant something to join with. Finally, new sealant will be installed and “tooled” smooth for a clean-edged, nice-looking finish.