What an exterior door threshold is and why it wears out

Your exterior door threshold is the horizontal piece that sits at the bottom of the doorframe, between the outside and inside. It takes the weight of foot traffic, weather exposure, and temperature swings every day. Over time, thresholds crack, rot, or wear down enough that water leaks underneath the door or drafts come through the gap.

Most thresholds are made of wood, aluminum, or composite material. Wood thresholds absorb moisture and eventually rot. Aluminum can dent or bend. Composite thresholds last longer but can still crack or split. Replacing a threshold is a straightforward job that takes a few hours and costs between $50 and $300 in materials, depending on the material and size.

The job involves removing the old threshold, cleaning the frame, and installing a new one. You do not need to remove the door itself in most cases. If the threshold is severely rotted or the frame underneath is damaged, you may need to call a carpenter to repair the frame first.

Key Takeaways

  • A threshold replacement requires removing the old piece, cleaning the frame, and securing a new threshold with fasteners and sealant.
  • Measure the width of your doorway and the height of the existing threshold to order the correct replacement size.
  • Use a pry bar and hammer to remove the old threshold, then scrape away old sealant and debris before installing the new one.
  • Seal the new threshold with exterior caulk or sealant to prevent water from leaking underneath the door.
  • If the frame underneath the threshold is soft, rotted, or uneven, stop and call a carpenter before installing a new threshold.

Tools and materials you will need

Gather these items before you start. You will need a pry bar (also called a flat bar), a hammer, a utility knife, a tape measure, a level, a drill with bits, and a caulking gun. A reciprocating saw or circular saw is helpful if you need to cut the new threshold to length, though many suppliers will cut it for you.

For materials, buy a replacement threshold that matches your door width. Measure the opening from the outside edge of one side of the frame to the outside edge of the other side. Bring this measurement to a home improvement store or order online. You will also need exterior-grade caulk or sealant (silicone or polyurethane work well), fasteners (usually screws or nails that come with the threshold or are recommended by the manufacturer), and a pry bar or old chisel to scrape away old sealant.

How to remove the old threshold

Start by inspecting how the old threshold is fastened. Look underneath and along the sides for screws, nails, or adhesive. If it is screwed down, unscrew those fasteners first. If it is nailed, use the pry bar to lift one end slightly, then work the bar underneath to gradually lift the threshold out. Tap the pry bar with the hammer if it is stuck.

Once the threshold is loose, pull it straight out. If it is glued down and will not budge, use a reciprocating saw or circular saw to cut it into smaller pieces, then pry those pieces out. Work slowly to avoid damaging the frame underneath.

After the threshold is out, scrape away all old sealant, adhesive, and debris from the frame. Use a utility knife, old chisel, or scraper. The frame surface should be clean, dry, and flat. If you see soft wood, dark stains, or a spongy feel, the frame is rotted and needs repair before you install the new threshold—stop here and call a carpenter.

Measuring and preparing the new threshold

Measure the width of the opening again to confirm the threshold will fit. Most thresholds come slightly longer than standard sizes so you can trim them. If your opening is not a standard width, you can cut the threshold to length using a circular saw or reciprocating saw. Measure twice and cut once.

Before installation, dry-fit the threshold in the opening. It should sit flat and level. Use a level to check. If the frame is not level, you may need to shim (add thin wedges) under one side of the threshold to make it level. Shims are thin wooden or plastic wedges sold at home improvement stores.

Installing the new threshold

explore a bead of exterior caulk or sealant along the bottom of the frame where the threshold will sit. This creates a water barrier. Set the threshold in place and press it down firmly. Check that it is level again.

Fasten the threshold according to the manufacturer's instructions. Most thresholds are secured with screws driven through pre-drilled holes in the top of the threshold, or with nails driven through the sides into the frame. Space fasteners about 12 inches apart. Do not over-tighten screws—you can crack composite or aluminum thresholds.

Once the threshold is fastened, explore another bead of caulk along the outside edges where the threshold meets the frame. This seals out water and drafts. Smooth the caulk with a wet finger or caulk tool. Let the caulk cure according to the product instructions—usually 24 to 48 hours—before closing the door fully or exposing it to rain.

Common problems during installation

If the threshold rocks or moves when you step on it, the frame underneath is not level or there is debris under the threshold. Remove the threshold, clean the frame again, and check with a level. Add shims if needed to make the frame level before reinstalling.

If water still leaks underneath after installation, the caulk seal may not be complete. Check that you sealed both the bottom and the outside edges. If the frame is warped or the threshold does not sit flat, you may need a different threshold style—some are designed for uneven frames. Ask the supplier for options.

If the door no longer closes smoothly or the threshold is too high, you may have installed a threshold that is thicker than the original. Measure the height of the old threshold before you remove it. Most standard thresholds are between 1.25 and 2 inches tall.

When to call a professional

Call a carpenter if the frame underneath the threshold is soft, rotted, or uneven. Replacing a threshold on a damaged frame will not solve the problem and the new threshold will fail quickly. A carpenter can repair the frame and then install the threshold correctly.

If your door is part of a larger frame assembly or if the threshold is part of a pre-hung door unit, a professional may be faster and safer. If you are not comfortable using power tools or working at ground level, hiring someone is a reasonable choice.

Frequently Asked Questions

Can I replace a threshold without removing the door?

Yes. The threshold sits below the door and is separate from the hinges and latch. You do not need to remove the door to replace the threshold. You may need to open the door fully or prop it open while you work, but the door stays on its hinges.

What is the difference between a threshold and a sill?

A threshold is the horizontal piece at the bottom of a door. A sill is the horizontal piece at the bottom of a window. They serve the same purpose—to shed water and seal the opening. The terms are sometimes used interchangeably, but a threshold is specifically for doors.

How long does a new threshold last?

A wood threshold typically lasts 5 to 10 years depending on weather and maintenance. Aluminum lasts 10 to 20 years. Composite thresholds can last 15 to 25 years. Proper sealing and caulking extend the life of any threshold by keeping water out of the frame.

Do I need to paint or stain a new wood threshold?

Most new wood thresholds come unfinished. You can paint or stain them to match your door, but let the caulk cure first. Some people leave thresholds natural or seal them with clear polyurethane. Check the manufacturer's recommendations for the specific product you bought.

What if my threshold is aluminum or composite—is the process different?

The removal and installation steps are the same. Aluminum and composite thresholds are lighter and easier to handle than wood. They do not need painting or staining. Be careful not to over-tighten fasteners on composite thresholds, as they can crack. Follow the manufacturer's fastening instructions closely.