Water leaking through or around a door damages flooring, subfloor material, the door frame, and the wall structure. In coastal and high-rainfall areas, this is a recurring problem that worsens with each storm if left unaddressed. Prevention starts with understanding where water enters and maintaining the components that keep it out.

Where Water Enters Around Doors

Water finds its way in through several points around a door assembly.

The threshold is the horizontal surface at the bottom of the door opening. If the threshold is damaged, improperly installed, or has shifted, water pools at the base and seeps under the door. Adjustable thresholds that have settled over time leave gaps that allow water to pass through.

The weatherstripping along the sides, top, and bottom of the door creates a compression seal when the door is closed. Weatherstripping that is worn, compressed, or torn breaks the seal and allows water to enter during wind-driven rain.

The frame-to-wall junction is where the door frame meets the exterior wall cladding. Caulking and flashing at this junction direct water away from the opening. When caulking cracks, shrinks, or separates, water penetrates behind the frame and enters the wall cavity.

The door sweep at the bottom of the door contacts the threshold to create a barrier against water and air. A missing, worn, or poorly fitted sweep allows water to pass under the door.

Maintaining the Threshold

Inspect the threshold at least twice a year, once in spring and once before the winter heating season. Look for cracks, dents, corrosion, and movement. Run your hand along the threshold surface while the door is closed to feel for gaps.

Adjustable thresholds have screws along the top surface that raise or lower the height. Adjust the threshold so the door sweep makes firm, even contact across the full width. If the threshold is damaged or corroded beyond adjustment, replace it.

Apply a bead of exterior-grade sealant along the base of the threshold where it meets the floor or sill plate. This prevents water from wicking underneath.

Replacing Weatherstripping

Weatherstripping wears out. This is normal and expected, especially on exterior doors that open and close multiple times per day. Plan to replace weatherstripping every two to five years depending on use and exposure.

Remove the old weatherstripping and clean the channel or surface where it was mounted. Install new weatherstripping that matches the door type and profile. Compression weatherstripping, magnetic weatherstripping, and bulb weatherstripping each have specific applications.

Test the seal by closing the door and sliding a piece of paper between the door and the frame. If the paper slides freely, the weatherstripping is not making enough contact. Adjust or replace as needed.

Caulking & Flashing Maintenance

The caulk joint between the door frame and the exterior wall should be inspected annually. Look for cracks, gaps, and separation. Remove old caulk that has failed and apply a new bead of exterior-grade silicone or polyurethane sealant.

Flashing above the door directs water away from the top of the frame. If flashing is missing, bent, or improperly overlapped, water runs down behind the frame. Verify that the flashing extends past the casing on both sides and directs water outward, not behind the wall.

On doors with sidelights or transoms, the joints between the frame components need the same caulking and flashing attention.

Installing a Door Sweep

A door sweep attaches to the bottom of the door and contacts the threshold when the door is closed. Sweeps wear down from friction and should be replaced when they no longer make even contact.

Choose a sweep material that matches the door’s use. Rubber sweeps are durable for exterior doors. Brush sweeps work well for interior doors or doors that cross uneven thresholds.

Mount the sweep so it contacts the threshold evenly without dragging excessively. Too much contact creates resistance and wears the sweep faster. Too little contact leaves gaps for water to enter.

Grading & Drainage Around the Door

Water that pools at the base of an exterior door eventually finds a way in. The ground surface immediately outside the door should slope away from the opening. If water pools at the threshold during rain, the grading needs attention.

Concrete stoops, patios, and walkways should drain away from the door. Verify that the surface has a slight slope away from the building. If the surface is flat or sloped toward the door, regrading or adding a channel drain redirects water before it reaches the threshold.

Gutter downspouts that discharge near a doorway should be redirected. Splash blocks and downspout extensions carry water away from the foundation and door area.

Seasonal Inspection Checklist

At the start of each season, inspect the threshold for damage and adjustment. Check weatherstripping for compression and wear. Examine caulking around the frame for cracks and separation. Verify that flashing is intact and directing water properly. Test the door sweep for even contact. Clear debris from the threshold and door track.

These steps take a few minutes per door and prevent the cost and damage of a water leak.