It's common for storm doors to sag due to years of use or wear and tear, but it can be bothersome when a storm door won't close properly. Immediate repair is necessary if this door is displaced from its alignment. Otherwise, it may lead to more damage both on the door and the floor where the door rests.
Most storm doors have metal frames screwed to a wood molding. The door might sag, scrape or bump the doorjamb when the screws or molding become loose.
Fixing Screen Door Out of Square
First, inspect the condition of the screen door and the extent of the Larson storm door sagging or whichever brand of door you have. Next, look at the hinges and see if there is anything lose or missing.
Sometimes, simply replacing the screws of the hinge with a new set should put the screen door back in its proper alignment. If possible, choose screws that are slightly larger than the original as this will hold the hinges in place better.
Adding a Shim
It might also help to install a shim to reduce the wear and tear and fix the sag. To do this, unscrew the bottom hinge and clean off any dirt or debris. Then, place a strip of wooden shim or cardboard by the hinge. Screw everything back in place, then check the alignment by opening and closing the door.
If the screen door is out of the square still, you might need to do take out the shim and replace it with a thicker kind.
Installing the Turnbuckle
A screen door turnbuckle works like a brace that reinforces the door. It's a metal rod with threaded ends that attach to a coupling nut. Though it will fix the sag, adding a turnbuckle will change how your screen door looks aesthetically.
Flatly position the turnbuckle by the bottom corner of the door. It should extend diagonally below the side that opens, then all the way up to the side of the hinge. Open and close the door to make sure that the turnbuckle isn't blocking the door seal, then mark its screw holes with a pencil.
Next, drill the turnbuckle's screws but don't tighten it yet until all the holes are set. Open and close the door again to make sure that the adjustments are right, then tighten the screws to pin the turnbuckle in place.
Hold the turnbuckle's coupling nut and watch as the rods lift the side of the door that's sagging. Turn the nut until the door is leveled off. You should feel the turnbuckle getting pretty tight so adjust accordingly if it's too tight.