How to Apply Elastomeric Caulk to the Right Angle of a Concrete Joint

Vacuum the concrete joint once the backer rod is in place. This removes any loose debris that would prevent the caulk from adhering properly.

Cut the end of the elastomeric caulk tip at a 45-degree angle with a utility knife. The tube tip has five lines, each representing a different bead width to accommodate the joint you are filling. Most joints that are right angles near a wall require the tube tip cut at the third line for a 1/2-inch bead.

Insert the sharp end of a 16d nail into the center of the tube tip and pierce the foil covering inside the tube. Take the nail out of the tube tip. Place the tube inside the caulk gun with the open side of the 45-degree angle on the handle side of the gun.

Start at one end and squeeze a steady bead of elastomeric caulk into the concrete joint. Hold the gun at a 45-degree angle to the wall with the tip of the tube on top of the joint. Fill the joint completely with the elastomeric caulk just above the joint surface. Do not smooth the caulk with your fingers. The caulk will seal level and smooth as it cures, which takes approximately 24 hours.