Doors and Hardware
An exterior door may be more energy efficient than a window, but a door can leak just as much water and air. As the moisture content changes in soil, your home shifts. Your doors also shift, creating gaps large enough for a dump truck to pass through.
With doors, you need to regularly caulk the exterior trim even if the exterior door in question is protected by a covered porch. Remember that caulking is designed to keep out air as well as water. Caulk the doorframe to the door trim and the door trim to the siding.
If you find moisture on the entry floor, it could be a leak between the threshold and the door bottom. The threshold is the wood or metal platform at the base of the doorway. It usually tilts outward to shed water. The bottoms of most exterior doors are fitted with a metal door bottom or "shoe" that houses a rubber gasket. The door shoe is attached to the bottom of the door with screws driven through oblong slots in the shoe. The oblong slots allow the door bottom to be adjusted up and down as the house -- and consequently the door -- shift up and down. When the door is closed, the rubber gasket is supposed to rest tightly against the full length of the threshold preventing the influx of air and water.
No matter how successfully the door shoe and threshold work to prevent air and water leaks, there could be yet another problem. The threshold itself might leak. Exterior door thresholds are normally laid in a thick bed of caulk when originally installed. Occasionally, the caulk shrinks and the threshold leaks. The only way to prevent future leaks is to remove the threshold, recaulk the area, and replace the threshold. Be sure to readjust the door shoe once the threshold has been replaced.
Stopping air leaks
An air leak in a doorframe is pretty common. Use the candle test described earlier to see just how severe the problem is.
Foam sealant can be added between the frame of the door and the frame of the house by removing the interior door casing. The casing is the wood trim that covers the joint between the doorframe and the wall. Use a flat pry bar to slowly remove the trim so that it won't be damaged.
Other air leaks can occur between the door and the doorframe. This is where weather stripping is handy. It doesn't make any difference whether the exterior door is painted or stained, large or small, solid wood or French style, the same type of weather stripping can be used. We like the kind of whether stripping that consists of a rubber bead attached lengthwise to a strip of metal. Standing outside the door, with the door in the closed position, gently press the rubber portion of the weather stripping against the door and frame at the same time. Attach the metal section of the weather stripping to the frame of the door with the nails or screws provided. Here, oblong holes allow the weather stripping to be adjusted later as house movement causes the door to shift.