Weatherstripping Door Frames

Air leaks can account for 20% to 30% of the total heat loss of an insulated house. If your budget is tight, sealing seams and holes in the building envelope, packing insulation into the gaps around windows and doors, and installing weatherstripping should be your first priority. The single most crucial piece of weatherstripping is a tight-fitting door threshold.

Weatherstripping Jambs
Today, there are three main types of weatherstripping: tubular, metal-leaf, and kerf-in. Most are easy to install and require few special tools. Prehung exterior doors typically come with weatherstripping attached, which can be easily removed before installing the unit so you can better see the 1⁄8-in. reveal between the door and the jambs. Door shoe gaskets (which seal the bottom of a door) are removed for the same reason.

Tubular is the easiest to retrofit to old doors and the least expensive type of permanent weatherstripping. The reinforced part of the strips is usually metal, with slots for screws; slots allow you to adjust the stripping so it fits tight to windows or doors. To install tubular weatherstripping, shut the door and press the strip’s flexible seal against the door, then screw the reinforced part to the jamb. Don’t buy tubular stripping that nails up or has round holes (not slots) because it can’t be adjusted.

Metal-leaf, commonly called a V-bronze or metal tension strip, is a thin metal strip folded lengthwise and nailed with brads to door jambs. When the door shuts, it compresses the metal, stopping drafts. Metal tension strips are durable and, because they fit between the door or window and the frame, are hidden when the door is shut. When installing it, place the leaves flush to the doorstop, spacing brads every 3 in. Install the head piece first, then the sides. To keep the leaves from snagging where they meet in the corners, snip them back at a slight angle (5°). In time, the leaves flatten, but they can be raised by running a flathead screwdriver down the center of the fold.

Kerf-in features flexible stripping (silicone, vinyl, or nylon) that slides into a kerf (slot) between the jamb and the doorstop. Kerf-in is the preferred weatherstripping for prehung exterior doors because it seals tightly and can be easily replaced if the stripping gets compressed over time. To cut kerfs into existing frames, use a kerfing tool, which looks like a laminate trimmer on an angled base. Silicone stripping is a good choice for retrofits because it compresses so small that old doors shut easily without doorstop adjustments. At head-jamb corners, cut stripping at 45° angles so it lies flat.

Sealing Under the Door
Weatherstripping at the bottom of a door must create a tight seal and be durable. Elements that attach to door bottoms are called shoes or sweeps; those that attach to doorsills are thresholds. Although primarily intended to reduce drafts, they also must resist water seeping or blowing in under the door. If your region gets a lot of precipitation, a roof or porch overhang should be your first line of defense—properly sized, the overhang should extend out from the building half the distance from the doorsill to the underside of the eave.

Attaching sweeps and shoes. If you’re fortunate enough to have an outswing door, install a compressible gasket to the integral stop in the threshold and a flap neoprene sweep to the outside of the door. On an outswing door, cut the sweep to length and hold it against the bottom edge of the door so the sweep just touches the threshold when the door is shut. Flap sweeps are not as durable as kerf-in sweeps, but they’re inexpensive, easy to install, and reasonably durable.

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