How to Install an Exterior Door Threshold | Done Right

A worn or drafty threshold wastes energy and invites water damage. Replacing it is a straightforward DIY job that stops both problems at once. The sequence is the same whether you have a wood, metal, or composite threshold: remove the old, prep the base, fit the new, seal everything, then adjust the door. This guide walks each step so your new threshold stays dry and seals for years.

Removing the Old Threshold

Cut the old threshold in the center with a reciprocating saw, then cut through any visible fasteners. Pry the pieces out with a pry bar; if the threshold is nailed tight, cut it into manageable sections first. Work carefully near the door jambs and flooring to avoid damage. Once the threshold is out, inspect the subsill or subfloor beneath it. Rot or uneven spots need repair before you proceed — installing over a bad base guarantees a short life for the new threshold. If the wood below is sound, sweep away debris and let the surface dry.

Measuring and Cutting the New Threshold

Measure the doorway width at floor level between the jambs, then measure again at the middle and top of the same opening. Use the smallest measurement for your cut. Lay the new threshold in place and mark the length with a pencil. A hacksaw works for metal or composite; a miter saw or jigsaw handles wood.

Dry-fit the threshold before reaching for adhesive. Check that the ends clear the door stops and jambs without binding. If the threshold needs notches to fit around casings or stops, cut them now. A dry-fit that sits flat with no rocking or gaps means you are ready for the next step. For a wide selection of replacement thresholds that fit standard openings, our roundup of the best exterior door thresholds covers wood, metal, and composite options side by side.

Sealing and Fastening the Threshold

Apply a generous bead of construction adhesive or silicone caulk along the subsill where the threshold will sit. Also run sealant under the full length of the legs and across both ends — water and air enter through the edges most often. Some installations also benefit from low-expansion polyurethane foam under the threshold to fill small gaps and add insulation; just avoid high-expansion foam, which can lift and distort the assembly.

Set the threshold in place and press it into the sealant. If the threshold has predrilled holes, align them now; otherwise, mark your screw locations, then drill pilot holes to prevent splitting. Fasten the threshold with exterior-grade screws or corrosion-resistant nails. Drive them straight and snug, but do not overtighten to the point of warping the metal or cracking the wood.

Adjusting the Door Sweep and Checking the Seal

With the threshold secured, close the door. The sweep should contact the threshold evenly across its full width — no daylight, no drag. If the door bottoms out and won’t latch, the threshold is too high; remove it, trim the height, and reseal. If there is a visible gap, adjust the sweep downward or install a new sweep that reaches the threshold. Cycle the door several times to confirm it self-closes and latches smoothly. A successful install leaves the door operating exactly as it did before, but with a tight, draft-free seal at the bottom.