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How to replace an exterior door sill

Updated February 21, 2017

Exterior door sills can be constructed with aluminium, wood or a combination of both materials. Over time, the sill can deteriorate due to weather conditions, moisture or everyday wear and tear. Save time and money by replacing a damaged sill yourself. Door still replacement kids typically include fastener hardware as well as predrilled holes for installation purposes. Removing the old sill will most likely require you to cut the fasteners that are found between the sill and door jambs.

Open the door to expose the threshold and sill. Remove the fasteners that secure the threshold to the door sill. Pull out the threshold to expose the top face of the door sill.

Cut through the fasteners that secure the sill to the door jambs by slipping the reciprocating saw's cutting blade between the two. Repeat this process on the opposite side.

Inspect the door sill's top face to locate the fasteners that secure it to the rough framing of the door opening. Remove the fasteners by pulling or unscrewing them with the appropriate tools such as a nail pull and a hammer or a screwdriver.

Slide the sill from under the door jambs. Dislodge the sill by tapping the outside edge with a hammer if it does not slide out easily. Remove all dirt and debris from the area where the sill sat.

Compare the old sill measurements with the replacement to make sure it will fit properly. Slide the new sill into place under the door jambs. Check that the outer lip sits flush against the building when it is slid into place and that it is level.

Follow the manufacturer's recommendations when fasteners are used to secure the sill into place; screws or nails are sometimes included with the sill packaging. Place a bead of exterior caulk around the outer edges of the sill to prevent moisture and insects from getting underneath.

Place the threshold between the door jambs. Place the screw fasteners through the threshold and into the sill to secure it into place.

Open and close the door to make sure that the threshold and sill work properly. Check to make sure there aren't any gaps between the threshold seal and the bottom edge of the door.

Warning

When using a reciprocating saw to cut metal fasteners, wear safety glasses to protect your eyes from metal shavings.

Things You'll Need

  • Screwdriver set
  • Hammer
  • Nail pull
  • Reciprocating saw
  • Replacement sill
  • Level
  • Exterior caulk
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About the Author

Elizabeth Arnold has written for a wide variety of publications and websites. Her experience includes writing travel features for "Recommend" magazine and packaging marketing copy for both Metro-Goldwyn-Mayer and Warner Bros. consumer products. Recently, Arnold was a staff writer for "Special Events" magazine. Arnold studied English at the University of Wisconsin-Milwaukee.