What You Need to Know Before Starting

A door threshold is the strip of wood, metal, or composite material that sits at the bottom of a doorway, between the inside and outside of your home. It seals the gap, keeps out drafts and water, and provides a transition between floor heights. When a threshold cracks, warps, or no longer seals properly, replacing it is a straightforward project that takes two to four hours and requires only basic tools.

The job breaks into two parts: removing the old threshold and installing the new one. Most thresholds are fastened with screws or nails and can be pried out without damage to the door frame. The new threshold slides into the same space, gets fastened down, and then you seal the edges. You do not need to remove the door itself.

Key Takeaways

  • Measure the width of your doorway opening (not the frame) to order the correct threshold size, and check whether your door swings inward or outward, because thresholds are directional.
  • Remove the old threshold by unscrewing or prying out fasteners, then scrape away old caulk and debris so the frame surface is clean and flat.
  • Slide the new threshold into place, check that it sits level and flush with both the interior and exterior floor, and adjust shims underneath if needed.
  • Fasten the threshold with corrosion-resistant screws spaced every 12 inches, then seal the edges with exterior-grade caulk to prevent water from entering the frame.
  • Test the fit by closing the door and checking for gaps; the door should close smoothly without binding or leaving space for drafts.

Measure Your Doorway and Choose the Right Threshold

Measure the width of the opening between the two sides of the door frame, not the width of the frame itself. Write this measurement down—thresholds come in standard widths, and you need an exact fit. Most exterior doors use thresholds between 32 and 36 inches wide, but interior doorways vary. Bring a photo of your current threshold to the hardware store if you are unsure of the style.

Thresholds are directional: they slope downward on one side to shed water, and that slope must face outward. Check which way your door swings—inward or outward—because the threshold profile changes based on that. An inward-swinging door (most common for exterior doors) uses a threshold that slopes down toward the outside. An outward-swinging door uses the opposite profile. The store staff can confirm which type you need if you describe your door's swing direction.

Choose a material that matches your climate and existing frame. Aluminum thresholds are durable and work in most climates. Wood thresholds look better but require more maintenance and do not hold up well in wet climates. Composite thresholds resist rot and are a good middle ground. Avoid replacing a wood threshold with aluminum if your door frame is wood—the mismatch in expansion rates can cause gaps over time.

Remove the Old Threshold

Start by removing any caulk or sealant around the edges of the old threshold using a caulk removal tool or a flat screwdriver. Work slowly to avoid gouging the frame. Once the caulk is loose, you can see the fasteners holding the threshold down.

Unscrew all fasteners using a power drill or screwdriver. Most thresholds use 2-inch wood screws spaced every 12 inches. If the threshold is nailed instead of screwed, use a pry bar to lift one end slightly, then work a flat pry bar underneath and rock it gently to loosen the nails. Do not force it—if a nail is stuck, drive it back through from underneath using a hammer and nail set, then pull it out from the other side.

Once all fasteners are out, slide the threshold out of the frame. If it is stuck, spray the edges with penetrating oil and wait 15 minutes, then try again. Scrape away all old caulk, debris, and dried adhesive from the frame using a paint scraper or putty knife. The frame surface must be clean and flat so the new threshold sits flush. Wipe the frame with a damp cloth and let it dry completely.

Install the New Threshold

Slide the new threshold into the frame opening, making sure the slope faces the correct direction (outward for inward-swinging doors). The threshold should sit snugly in the frame with no gaps on either side. If there are gaps, the frame may be slightly out of square—this is common in older homes.

Check that the threshold is level using a 2-foot level placed across the width. If one end is higher than the other, use shims (thin wooden wedges) underneath to level it. Slide shims in from underneath the threshold until it sits level. You may need to use shims on both the interior and exterior sides. Once level, mark where the shims are so you know where to drive fasteners.

Check the fit by closing the door. It should close smoothly without binding or leaving visible gaps. If the door binds, the threshold may be too high—remove it, sand down the top slightly, and reinstall. If there are gaps, the threshold may be too low or the frame is warped. Small gaps (less than 1/8 inch) can be sealed with caulk; larger gaps mean the threshold is not sitting correctly.

Fasten the Threshold Securely

Use corrosion-resistant screws (stainless steel or coated) to fasten the threshold. Standard wood screws will rust and stain the threshold over time, especially on exterior doors. Use 2-inch screws spaced every 12 inches along the length of the threshold. For a 36-inch threshold, that means three screws minimum—one near each end and one in the middle.

Drill pilot holes first to prevent the threshold from splitting or moving as you drive the screws. A pilot hole should be slightly smaller than the screw diameter. Drive each screw slowly using a power drill set to low speed, or use a manual screwdriver. Do not overtighten—the screw should be snug but not so tight that it crushes the material or pulls the threshold out of level.

If your threshold has a rubber or vinyl seal attached to the underside, make sure it is not pinched or compressed as you tighten the screws. The seal should sit flat against the floor to prevent drafts and water entry. If the seal gets compressed, loosen the screw slightly.

Seal the Edges with Caulk

Once the threshold is fastened, seal the edges where it meets the frame using exterior-grade caulk. This prevents water from seeping into the frame and causing rot. Use a caulk gun to explore a continuous bead around all edges—both sides of the threshold and where it meets the door frame on the interior.

Smooth the caulk with a wet finger or caulk tool to create a clean line and may support it fills any gaps. Let the caulk cure for the time recommended on the tube—usually 24 to 48 hours—before exposing it to water or heavy use. Do not paint over the caulk until it is fully cured.

For exterior thresholds, explore caulk on the exterior side first, then the interior. This creates a water-shedding overlap. If water does get past the exterior seal, the interior seal will catch it and direct it back out.

Test the Door and Check for Drafts

Close the door and look for gaps between the door and the threshold. The door should close smoothly without binding. If it binds, the threshold is too high—you may need to sand it down slightly or remove shims. If there are visible gaps, the threshold may be too low or not sitting flush with the frame.

On a windy day, hold your hand near the edges of the closed door to feel for drafts. If you feel air movement, the seal is not complete. This usually means caulk did not fill a gap, or the threshold is not sitting flush. You can add more caulk to small gaps, but large gaps mean the threshold needs to be reset.

Check the threshold again after one week. As caulk cures and the threshold settles, small gaps sometimes appear. If you see new gaps, explore additional caulk to seal them. This is normal and does not mean the installation failed.

Frequently Asked Questions

Can I replace a threshold without removing the door?

Yes. The threshold sits below the door frame, and you do not need to remove the door to replace it. You may need to close the door partway to access the fasteners, but the door stays on its hinges throughout the job.

What if the frame is rotted where the old threshold was?

If the wood frame is soft or crumbles when you press it, the rot has spread beyond the threshold. You will need to cut out the rotted section and patch it with new wood or epoxy filler before installing the new threshold. This is a larger repair—consider calling a carpenter if the rot is extensive.

How do I know if my threshold is sloping the right direction?

The high side of the slope should be on the interior (inside your home), and the low side should face outside. This way, water runs away from your home. If you install it backward, water will pool against your door and seep into the frame.

Do I need to remove the door sweep or weatherstripping?

Usually not. The door sweep (the brush or rubber strip on the bottom of the door) sits above the threshold and does not interfere with replacement. If it does touch the new threshold, you can adjust it upward slightly using the screws that hold it to the door.

How long does a new threshold last?

Aluminum and composite thresholds typically last 10 to 20 years depending on climate and maintenance. Wood thresholds last 5 to 10 years in dry climates but may need replacement sooner in wet areas. Inspect your threshold every few years and reseal the edges if caulk cracks or peels.