Years of weather and use eventually cause a storm door to sag. A sagging storm door is difficult to open and often does not latch properly. Fixing a sagging storm requires reattaching the hinges or adjusting the hinge side of the door frame. As the home ages, the door jamb moves in and out due to expansion and contraction from outside temperatures. This causes hinge screws to become loose and even causes the door jamb to move. When installing new screws into hinges, it is a good idea to use larger-diameter screws. This will ensure that the screws get a good "bite" into the frame and hold the hinge.
Open the storm door and inspect the hinges. Sometimes the hinge screws come loose or fall off either the frame or the door. When this happens, the hinge bends away from the door jamb, causing the door to sag.
Replace missing or loose hinge screws with new sheet metal screws. Remove a good screw from a hinge with a Phillips-head screwdriver. This will give you an idea of what size screws you need. Purchase sheet metal screws slightly larger in diameter than the original to ensure that the new screw will secure the hinge. Install the screws into the hinge as necessary with a Phillips-head screwdriver. Tighten the hinge screws so that all hinges sit flush on the edge of the door and the door jamb.
Remove the screws securing the hinge side of the storm door frame on the inside door jamb, if the hinge screws are in place. Go outside and close the storm door. Remove the screws securing the hinge side of the storm door frame to the outside of the house with a Phillips-head screwdriver. It may be necessary to remove the two end screws securing the upper drip cap to allow movement of the storm door frame.
Insert shims under the latch side corner of the storm door, between the bottom of the door and the door sill. Place the edge of a small scrap of wood on the inside edge of the storm door frame near the top corner. Gently tap the wood with a hammer to tap the top of the storm door frame against the door jamb.
Drill new pilot holes to reattach the storm door frame to the outside of the home. Install the securing screws to secure the door frame. Open the storm door and install 3-inch-long wood screws into the door frame and inside door jamb. Tighten the upper drip cap screws, if necessary, and fill in any empty securing holes on the outside of the door frame with silicone caulk and a caulking gun.