How to Waterproof and Seal an Exterior Door

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Your exterior doors can become weak points in your home's insulation blanket over time. Older doors may not have any water and wind intrusion barriers at their edges, while newer doors may have weatherstripping that's deteriorating and no longer provides sufficient weather resistance. Fortunately, replacing worn or missing seals on your entry doors is a quick, straightforward project that saves energy costs. Here's how to waterproof and seal your exterior doors.

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Repairing a Warped Door

A warped door situation can cause weatherstripping failure by creating air gaps or prematurely wearing out the seal. Repair warped doors before sealing and waterproofing them by sanding down high spots, drying out damp wooden doors, or adjusting the door stops.

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Sealing Wooden Doors

Wooden doors are especially susceptible to water damage from rain and humidity. If your door has a cracked or worn finish, remove the previous covering by sanding and reapply stain and three coats of polyurethane or two coats of paint.

Sealing Air Gaps

Air can easily pass by the edges of the door where it meets the frame if there is damage to the weather seal. First, determine the correct weatherstripping for your door frame.

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Kerf Weatherstripping

Newer-style doors often have a kerf weather seal.

  1. To remove the strips, use a regular screwdriver to pry out a small section and carefully pull the rest free of its installation channel.
  2. Replace it with new pieces by firmly inserting the new ribbed flange into the channel.
  3. Cut the ends with a utility knife to fit the frame.

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EPDM Weatherstripping

Doors without a kerf seal can use self-adhesive EPDM weather seals.

  1. Remove remnants of the old seal with a utility knife and scraper.
  2. Install the new pieces by peeling away the backing from the adhesive strip while pressing the strips in place.
  3. Use gentle pressure when installing to avoid stretching the material.
  4. Cut the ends to fit the frame's top and sides.

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Nail-On Weatherstripping

Some doors don't have enough clearance between the door and its jambs to install EPDM strips. In that case, or if the strips would impede the function of the door hardware, frame-mounted nail-on weatherstripping is available.

  1. Trim each strip as needed by cutting the metal flange of the strip with a hacksaw and cutting the rubber portion with a utility knife.
  2. Close the door and rest the rubber seal against the face of the door. The rubber should compress lightly against the door.
  3. Nail through the metal, the flange, and into the door frame to secure the strip.

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Waterproofing the Door Bottom

The bottom edge of any entry door can allow rainwater to enter the house if its door sweep is missing or needs replacement. Here's how to replace an old exterior door sweep.

  1. Remove the installation screws and the old door sweep.
  2. Close the door and mark the frame edges on the door slab.
  3. Transfer the marks to the new door sweep and cut it to fit with a hacksaw and utility knife.
  4. Hold the door sweep in place to fill the gap between the door slab and the threshold.
  5. Mark the screw hole locations on the door and remove the sweep.
  6. Predrill the holes before installing the new door sweep with new screws.

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