How do I weatherstrip a drafty door?

Weatherstripping a drafty door is usually a one-afternoon job. Seal the top and both sides with weatherstripping that the door presses against when it closes, seal the bottom with a door sweep or threshold, and caulk any gap where the trim meets the wall. The work is worth doing: the Virginia Energy Savers Handbook notes that doors may often leak even more than windows.^[2]

Find where the air is getting in

Before you buy anything, work out which part of the door leaks. ENERGY STAR lists the usual signs of air leaks around a door: drafts around a closed door, visible gaps around the trim, pests and dust getting in, outside odors and peeling paint around the frame.^[5]

Three quick checks narrow it down:

• Feel and watch. On a windy day, run your hand slowly along the top, both sides and the bottom of the closed door. Smoke from an incense stick bends toward or away from a leak.
• Look for light. With the interior and exterior lights off, one person moves a flashlight slowly around the outside edge of the closed door, and if a helper inside the house can see light shining in, weather-stripping is needed.^[1]
• Close it on paper. Shut the door on a sheet of paper in a few places. If the paper slides out with no drag, the seal at that spot is not touching.

Note whether the leak is at the edges of the door, under it, or around the frame. Each has a different fix.

Pick the right weatherstripping

The handbook says both sides and the top of a door should be weatherstripped with compression-type weatherstripping, and that the strip should be not so thick that it makes the door hard to close.^[2] The common choices:

• Self-stick foam or rubber tape. Cheap and quick to fit on the door stop. Frost King says its EPDM rubber tape won't harden, crack or freeze, even at 40 below zero.^[4]
• V-strip (tension seal). A folded vinyl or metal strip that springs open in the gap. The handbook suggests V-strip, which interferes less with opening and closing, for doors that bind with a thicker strip.^[2]
• Kerf-in or magnetic replacement seals. Steel doors often have magnetic weatherstripping, magnetic strips set in flexible neoprene rubber,^[2] and many newer doors hold the seal in a slot in the frame. Replace these with the same profile rather than sticking tape over them. Take a piece of the old seal to the store to match it.

For the bottom, the handbook recommends either a door sweep that attaches to the door or a vinyl-bulb threshold that creates a seal under it.^[2] A sweep is the easier fit, and Extension notes that it is connected at the bottom of the door, either inside or outside, depending on how the door moves.^[1] If you choose a gasket threshold, Extension notes that this type of gasket wears quickly in high traffic areas.^[1] A worn threshold insert can often be pulled out and replaced without removing the threshold.

Fit it so the door still closes

Adhesive strip fails early when it goes on a dusty or cold surface. Frost King's instructions call for surfaces completely dry and free of dust, grime or grease,^[3] and say a little warm water and soap is enough to clean off loose dust or oil.^[4] For its EPDM tape they give an installing range of roughly between 40 and 90°F;^[3] for any other strip, follow the temperature on its label.

For Frost King's EPDM tape on a typical inswing door, the strip goes on the door stop molding across the top and down the hinge side, and on the inside of the door across the top and down the latch side.^[3] Extension puts it on the jamb so the material creates a seal with the exterior face of the door on the top and both sides.^[1] Run it in one continuous piece where you can, and butt the corners tightly; a gap at a corner leaks like a gap anywhere else.

Then close the door and test it. The door should press against the strip and latch without a hard push. If you have to lean on it, the strip is too thick or set too far out, and over time it will strain the latch and hinges. Swap it for a thinner profile or a V-strip.

Seal the frame and the threshold

New weatherstripping only stops air between the door and the frame. Air also comes around the frame itself, which is why the handbook pairs weatherstripping with caulking around the door frame, between the trim and the wallboard.^[2] It also suggests you caulk the threshold with clear silicone if air gets in under it.^[2]

Outside, an exterior sealant closes the joint between the door trim and the siding or brick. Follow the label: DAP's exterior sealant, for example, is applied between 40°F and 100°F and not when freezing temperatures are forecast within 24 hours, and is meant for joints no wider than 1 inch and no deeper than 1/2 inch, with foam backer rod in deeper gaps.^[6]

When the door itself is the problem

Weatherstripping cannot fix every door. The handbook notes that some warping can be handled with weatherstripping, but a severely warped door should be replaced.^[2] A door that rubs at the top corner, has an uneven gap along the latch side, or will not latch after the new strip goes on may have loose hinges or a frame that has moved. Tightening the hinge screws often helps; a frame that is out of square is a repair job.

Older houses need one more check. If your home was built before 1978, or the work means disturbing paint, ENERGY STAR points you to the EPA's lead-safe renovation resources first.^[5] Scraping off old weatherstripping or caulk on painted trim can disturb old paint. The EPA's renovation rule generally does not apply to homeowners working on their own pre-1978 home,^[7] but anyone paid to do work that disturbs paint in a pre-1978 home must be certified in lead-safe work practices.^[7]

Stop and call a pro if

• The bottom of the door, the jamb or the threshold is soft, rotted or water-stained.
• The door is warped, sags or no longer latches even after the hinges are tightened.
• Water, not just air, comes in under the door or around the frame during rain.
• The house was built before 1978 and the job means scraping or sanding painted trim, and you would rather not handle the lead-safe cleanup.
• The draft turns out to come from a gap in the wall around the frame that is bigger than caulk or backer rod can fill.

If the draft is not only at the door, see where the biggest air leaks in a house are, and how often to check weatherstripping and caulk once it is done. You can browse handyman services, handymen around Blacksburg and the other handyman answers. For a door that needs more than new seals, describe the door repair once and local businesses quote it.