You may have an interior or exterior door in your home that used to work fine, but recently it's started to rub on the floor or against the jamb opposite the hinge jamb. To some degree, this is normal for wood doors hung in wooden jambs.
Gravity, combined with the door's opening and closing, works to pull the door down and off its hinges. The two forces can work hinge screws loose and can pull the door jamb away from the rough opening if the jamb was not properly installed.
The source of the problem may be a workmanship error at the time the door was hung, or it could be just normal wear and tear. The good news is, often the problem can be solved with a few common tools and very little effort.
Step back and look at the door with it closed. You want to be on the side of the door where you can see the hinges sticking out between the door and the door jamb.
Look at the gap between the door and the door jamb. It's probably uneven. It's supposed to be a uniform gap of one-eighth inch on both sides of the door and along the top of the door. The odds are you'll see a larger gap at the top of the door on the top edge that's above the handle or doorknob. The door is probably touching the side jamb at the top of the door, leaving no gap at all.
Open the door about 18 inches and stand on the other side of the door so you can see the hinges where they attach to the door jamb. Apply slow, but moderate, lifting force on the door knob. Look to see if the top door hinge on the door jamb moves ever so slightly. Have a helper look at the top hinge on the door edge as you lift. The movement will be very slight.
Use a screwdriver to tighten all of the screws on the top hinge only at this time. Tighten the screws that go into the door and the door jamb. Close the door and see if the gap between the door and the jamb has become more uniform and if most or all of the rubbing has been eliminated. If the door works perfectly, you're done.
If any of the screws have been stripped because they were overtightened now or in the past, you'll have to remove the screw and add new wood and carpenter's yellow glue. Coat wooden kitchen matches with glue and force into the screw hole. Tap them in with a hammer until they're flush with the mortised surface of wood under the hinge.
If the door still rubs after tightening the top hinge screws, tighten all screws on all the door hinges to see if that helps.
If the door still rubs, you may have to install one or two hidden 3-inch screws under the top hinge on the door jamb. Open the door at least 90 degrees and put shims, sticks or anything under the bottom end of the door under the door knob to provide support so the door does not droop or fall when you unscrew the top hinge from the jamb. Remove the top hinge from the door jamb, revealing the flat mortised area of the jamb.
Drill pilot holes that are one-sixteenth of an inch less in diameter than the shaft of the 3-inch screws in the flat mortised area where the hinge fits in the top door jamb. Position the new screws as close to the center of the door jamb as possible. That means the screw holes will be at one edge of the mortise area. This allows the screws to penetrate into the rough door jamb.
Space the holes at least 1 1/2 inches apart. Drive the long screws into the jamb and make sure the heads are flush or below the surface of the wood in the recessed mortise area. This will pull the door jamb tighter to the rough jamb.
SUMMARY: These simple steps will solve almost all drooping door issues. The long screws under the top hinge will almost always prevent future problems because they ensure the door jamb will not succumb to gravity.
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