How to Repair a Door Sill in a House

Written by mark morris
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How to Repair a Door Sill in a House
Make repairs to door sills quickly to avoid further damage (farmhouse door image by Michele Maakestad from

Doors and windows provide us with security and keep out inclement weather. Keeping sills, frames and weatherstripping in good repair is the key to getting the most out of your doors. The sill is the bottom most piece of the door frame. It is located underneath the threshold. The threshold is the metal or wooden piece that sits directly beneath the door when it is closed. To access the door sill for repairs, you may need to remove the threshold.

Skill level:

Things you need

  • Putty knife
  • Epoxy body filler
  • Sandpaper
  • Drill with screw bit
  • Hammer
  • Flat pry bar
  • Lumber door sill blank
  • 16 penny nails
  • Oil-based primer
  • Latex paint

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    Making Minor Repairs

  1. 1

    Examine the door sill. Sills that are cracked or chipped, but otherwise intact, can typically be repaired. If the door is missing pieces or shows signs of rot and deterioration, your best bet is to replace the sill.

  2. 2

    Repair sills with minor damage using two-part epoxy body filler. Brands vary, but the most common formulas come with a grey putty that makes up the bulk of the filler, and a red or yellow activator cream that is mixed in a ratio of 1 part activator to 10 parts putty. Blend the filler well with a metal putty knife on a disposable piece of plywood or lumber.

  3. 3

    Fill the damaged area with the mixed putty. Work quickly, as the putty begins to harden in under a minute. Smooth off the putty with the putty knife and allow to harden.

  4. 4

    Sand down the putty with sandpaper. A medium, 100 grit paper works best. Sand until the repaired area blends into the surrounding surface.

  5. 5

    Prime the repaired sill with oil-based primer, allow it to dry and apply two coats of exterior semigloss paint in the original sill colour to match.

    Replacing the Door Sill

  1. 1

    Remove the threshold. Back the screws out of the threshold and lift it out of position. If no screws are visible, remove the weatherstrip on top of the threshold to reveal the screw channel. Use a flat pry bar to lift the old sill out of its position. Start at one side and work your way across, levering the sill upward to release the nails holding it to the sill board.

  2. 2

    Cut sills that do not lift out easily down the centre with a circular saw. Set the blade to a depth that just cuts through the sill. Be careful not to cut any adjoining flooring. The force of the pry bar will be enough to complete the break if you cannot cut it completely through. Lift out the two pieces.

  3. 3

    Mark the new sill board to cut to the same length as the original. Make sure to purchase a sill blank the same width and thickness as the original. It may be helpful to remove the sill and take it with you to compare when shopping. (The door can still be closed and locked to maintain security.)

  4. 4

    Mark the end notches to fit the door frame. Use the original sill as a template to mark the ends of the new sill. Cut the notches with a jigsaw for best results.

  5. 5

    Prime all faces of the new sill with oil-based primer before installation. Allow it to dry then tap the sill into place using a rubber mallet or hammer and wood block. Nail the sill with a hammer and at least three 16 penny nails. Replace the threshold. Use new screws to attach the threshold to the sill. Replace any weatherstrip you may have removed in the process.

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