Buildings can settle immediately after construction or it can take years for some settling to occur.  The symptom of course is that your door will no longer lock when you close it or that you can’t close it. 

Unlike the warped door, no amount of force will make the door lock.  It can appear to be sagging similar to a door with loose hinge screws if you are only looking at the top of the door or it may be impacting the top of the jamb.  The difference here will be that the sides of the door will still be parallel to the jamb when the door may be rubbing on the top of the jamb or on the threshold.

The solution for this problem will require a little wood working for the wood jamb and an outside expert for a metal one. The tools needed for the wood jamb are;

·         A pencil

·         A chisel

·         A screwdriver

·         A tape measure

·         Wood rasp

·         A drill?

Use the screwdriver to remove the strike plate from the jamb.  Measure from the bottom of the door to the bottom of the bolt.  Then transfer that measurement point at the bottom of the bolt to the jamb.  Use the strike plate to center the hole for the bolt so that it has 1/8” of clearance.  Mark the top and bottom edges of the strike plate and the screw holes where they should be now.  You also need to mark the hole in the strike plate on any of the jamb that is visible.

You will need to chisel away enough wood to allow the strike plate to be mounted at the new location.  If the hole behind the strike needs to be enlarged, use the wood rasp to do that.  The drill will only be needed if you must plug the screw holes and make a pilot for the new one.

If your problem is that the door won’t even close, call in a professional to have the door modified to fit the new shape of the opening.