- 1). Loosen the wood by placing the blade of a chisel between the wood and cement, and hit the back end with a hammer. Pry out the damaged wood joint with a pry bar. Continue to remove the wood until you hit the bottom of the joint. Remove the entire length of the joint, or slightly more than the damaged area, in case the rot extends farther than you can see.
- 2). Use a leaf blower and wire brush to remove debris from the open joint.
- 3). Lay out a strip of foam backer rod beside the joint. The diameter of the backer rod should be one-eighth wider than the width of the joint. Measure the length of the open joint with measuring tape, and cut the backer rod to fit the space, using a utility knife.
- 4). Place the backer rod over the open joint and press it down as far as you can with your hands. Poke it down to the bottom of the joint with a putty knife.
- 5). Line the edges of the cement with painter’s tape to prevent stains on the patio surface.
- 6). Load a caulk gun with expansion joint urethane sealer, or apply it with a putty knife. Fill the remaining expanse of the joint and smooth the surface level with the putty knife. If the patio is tinted, choose a sealer that matches or complements the color. Remove the tape from the sides of the joint, and wait a full day for the sealer to set.
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