Doors provide access to the home. The biggest problems with doors are the hinges. When a door is properly installed the gap between the door jam and the door would be constant around the two sides and top of the door. This gap allows the door to open and close properly and for the expansion and contraction the door may have.
The door could never expand enough to prohibit the opening and closing of the door. Nor could the door grow in the opening. When the door is difficult to open and close and it drags on the floor it is usually the hinge that caused the problem. In some cases the jam comes out of plumb. This usually occurs when moving appliance through the door and you squeeze the appliances through. The way to check this is to measure the distance from side to side on the top and bottom of the jam.
If they are equal then you have to check for plumb. The best way to do this is with a plumb bob. Tack a piece of string, that is six inches shorter than the height of the door, on the top jam two inches away from one side jam. Tie a nut or bolt to the end of the string and let it hang until it stops moving. The string is now perfectly straight up and down. This is called plumb. Then measure the distance from the jam to the string at difference points on the jam.
If all the points you measure are equal then this side of the jam is plumb, if not, it's out of plumb. You will do the same for the other side of the jam. In most cases where you find the shortest measurement you can take a two by four and put it up to the jam and hit it gently with a hammer to bring the jam back into plumb.
Whenever you open and close a door a great deal of stress is put on the hinges. If the door becomes difficult to open and close, look at the gap between the door and the jam. This gap should be uniform on the sides and top. If both sides of the jam are plumb, look at the hinges. Open the door slightly and grab the knob and lift up on the door. The door should not move and if it does, the hinges will too.
This means the screws are loose that hold the hinge. The way to correct this is easy. Remove the screws from the top hinge that go into the jam. Dip some toothpicks in some carpenters glue and put them in the screw holes. Let this dry for a while.
Take a wedge, a Popsicle stick and your plumb bob and slip the wedge under the door to hold it steady. Tack the stick to the top of the door and extend it about two inches out from the side of the door. Tie the plumb bob to the end of the stick and let hang. Measure the distance from the door and the plumb bob at different points. Use the wedge to raise or lower the door until all the point are equal in distance. The door is now plumb. Screw the hinge back on and do the same to the rest of the hinges.
You should test the door opening and closing after each hinge is fixed. Installing weather-stripping, doors sweeps and thresholds to a door that is out of plumb will not work well and will not last long.