Poor installation, years of hard use, shifting foundations and seasonal warping can often force hinged doors and sliding glass patio doors to become out of square with their frames. If doors do not fit snugly, fix or replace the door, frame, hardware, gaskets and weatherstripping. The same techniques for preparing windows (as explained in Windows) apply to all doors including any needed repairs or adjustments, surface preparation and cleaning for the weatherstripping.

Weatherstrip the top and sides of the door frame as illustrated in Figure 8-8, Part A and Figure 8-8, Part B. The easiest and most effective weatherstripping for a door frame is a good quality V-shaped vinyl type. It makes contact with the edge of the door and provides a good seal even when the door warps from season to season.

For increased protection, attach weatherstripping to the stop so that it presses against the face of the door as shown in Figure 8-8, Part A.

There are also many types of combination metal and foam or rubber weatherstripping that are screwed to the stop. They should be adjusted regularly to conform to the changing warp of the door.

Apply weatherstripping to either the door sill (see the threshold in Figure 8-8, Part C) or to the door itself. Although this can be a difficult area to seal well, it is worthwhile doing because this is often a source of major drafts. Use durable material that can withstand traffic and is flexible enough to conform to changes in the door caused by fluctuations in humidity and temperature. The weatherstripping should also be easy to replace. A good seal can usually be obtained with gasketed door-bottom weatherstripping that attaches to the door, or with full or partial threshold weatherstripping that is attached to the door sill.

When the weatherstripping is applied to the door itself, a very durable material is necessary. The most effective choice is the combination type, which is simply tacked or screwed along the bottom inside surface of the door. There should be slots that allow for some adjustment of the weatherstripping.

There is a wide variety of door weatherstripping on the market, including kits that include weatherstripping and threshold or door bottom seals. Some products come with replacement seals. Look for high-quality, durable products.

For sliding patio doors, replace weatherstripping and hardware when worn. Replace poor condition sliding patio doors with ENERGY STAR® certified units or with French or garden-style doors and additional energy-efficient windows. In the interim, older patio sliding doors not used in winter can be sealed with removable sealant or covered with heat-shrink film.