Door sills degrade over time due to weather exposure and may need replacement. Sills or thresholds are attached at the base of the door opening. The sides of the sill are fastened to the side door jambs before the installation of the door. To replace a new sill, the old sill must be removed from the base of the door and the side door jambs. Nails or staples fasten the side jambs of the door to the ends of the sill.
Slide the flat bar underneath the side door casing. Pry the casing up and remove it from the door to allow access to the sill and expose the door jamb. Set the casing aside so that once the sill replacement is completed you can refasten it.
Saw across the existing sill close the side jamb of the door on both sides of the door opening with a hand saw to cut through the sill.
Remove the cut section of sill by prying it up with a flat bar and pulling it up from the floor. Use the claw of a hammer if necessary for added leverage.
Chisel out the remaining ends of the sill that are underneath the side jamb by placing the chisel against the floor and striking the sill in several spots to cut it into pieces and split it from around the fasteners. Use a mallet to strike the chisel if the wood is hard.
Cut the fasteners with diagonal cutters. Brush out the area where the sill was removed with a shop brush to clean the surface for the replacement.
Apply a bead of caulk along the underside perimeter of the replacement sill with window and door caulk using a caulk gun.
Slide the replacement sill into place. Tap the sill with a mallet if necessary to fit it perfectly in place.
Drill pilot holes approximately every 3 inches across the centre length of the replacement sill with a pilot hole bit. The holes should go through the sill and approximately 1/4-inch into the floor below.
Drive finish nails through the replacement sill at each of the pilot holes with a hammer. Set the nails 1/16-inch below the surface of the wood with a nail set.
Pull the nails from the side casing using the claw of a hammer. Align the casing in place from where you removed it. Drive finish nails through the existing holes to fasten the casing back in place. Set the nails 1/16-inch below the surface with a nail set.
Apply an exterior wood finish to the replacement sill.
Select a wood finish to match your existing trim or contrast it for added visual impact.
Wear eye protection when replacing door sills.