There are several reasons why you might need to repair a gate. Troubleshooting what is wrong with the gate usually lets you know what you need to repair. A sagging gate can be a result of wobbly posts, loose hinges, or an out-of-square gate frame. Gates sometimes begin sticking because they are retaining moisture. Usually, the gate is becoming unaligned, causing the hinges to loosen. The gate sags once the moisture is gone. Metal gates sag because the posts are wobbly or the pins that hold the gate to the post are bent. Here's how to fix it.
Step 1 - Check Stability of the Posts
The first step in troubleshooting a gate problem is checking the stability of the post supporting the gate and other posts near the gate. Make sure they do not wobble and they are plumb. Fence posts begin to wobble over time if they were made with untreated wood or their setting has become unstable.
Often, repairing the posts will fix your gate problems. You can secure a wobbly post with stakes or splints, but only if the post itself is still in good condition. Use two 2x4 stakes with bevel driving ends and drive the stakes into the ground on either side of the post. Make sure the stakes are treated with a preservative to prevent rotting. Secure together with bolts running through the post from one stake to the other.
If the posts are no longer in good condition, you will need to replace them. Unfortunately, this repair takes a great deal of work because you will need to replace the posts, disassemble, and reassemble the portion of the fence attached to the posts being replaced. Remove the posts and reinstall new posts, making sure you are using pressure treated wood, redwood, or cedar posts.
Step 2 - Check Quality of Hinges
Hopefully your posts do not wobble and the problem is with the hinges. Examine the hinges to see if they might be loose, bent, old, or too lightweight for your gate. Replacing hinges is relatively easy. You may also be able to fix your problem by simply replacing the screws attaching the hinges to your gate or post.
If the hinges are loose but appear to be in good condition, try removing the screws and filling the holes with dowel plugs the size of the original screw holes. Replace the hinges, using longer screws or carriage bolts.
Replace worn hinges with larger hinges, making sure to use new holes for the screws. To make a strap hinge stronger, bend its tip around a corner of the post.
Step 3 - Check the Gate Frame
If the posts do not wobble and the hinges look to be in good condition, check to see whether the gate frame itself is still square. If not, you can square it again by using heavy-duty turnbuckles and wire. Attach wire to screw eyes in the gate or fence framework at angles and place the turnbuckles in the center of the diagonal, tightening to square the frame or the fence.
By following these steps, you will be able to repair your gate.