- Examine both gateposts. Check the gateposts to make sure they are level (perfectly horizontal) and plumb (perfectly straight vertically). One or both of your gateposts may not be exactly upright. You can eyeball this, or use a spirit level for greater accuracy.
- Examine the hinges on the fence gate. On fence gates, each hinge is typically attached with two sets of lag bolts. A lag bolt (sometimes called a lag screw) is a steel screw used for wood projects. It looks like a screw, but the top is flat, thick, and hexagonal. Note the size of the bolt — 1/4-inch, 1/2-inch and 3/8-inch are common lag bolt sizes — in case you have to replace one that is rusted or missing.
- Disconnect the bottom hinge first. Even if the hinge looks perfectly fine, go ahead and disconnect it by removing the lag bolts with a ratchet or open-ended box wrench.
- Now, tackle the top hinge. Partially disconnect the hinge by removing only the lower lag bolt.
- Lift and shore up the leaning post. Set stones, bricks or blocks around the post to prop it up to the desired upright position. A spirit level will give you an accurate reading. You may have to dig around the post to reset it or replace a wooden one that has warped or rotted.
- Reset the top hinge. Once the post is level, reattach the lower lag bolt on the top hinge. Tighten it securely with a ratchet or wrench. Use blocks or stones to prop the fence gate erect or have a helper hold the fence gate steady and straight.
- Next, reset the bottom hinge. Don’t be surprised if you have to reposition the holes in the post: The old holes no longer match up due to wear. Rather than lift the fence gate, your best option is to drill new holes so that the fence gate remains aligned. Moving the hinge just this small amount will correct the angle and prevent the fence gate from sagging. Use a drill to make new holes that are slightly smaller than the screw you’ll use to attach the hinge. For example, use a 3/16-inch drill bit for a 1/4-inch screw.
- Replace the lag bolts on the bottom hinge. Tighten all the bolts on the top and bottom hinges and either oil the hinges or spray them with WD-40 or a similar lubricant so the fence gate will swing freely without creaking. Repeat these steps on the other gatepost if necessary.
- Heavy or long fence gates (such as a wooden driveway fence gates) may need additional support to keep them from sagging again. Installing guy wires — strong metal wiring that attaches fence gates to the tops of their posts — can help keep them level. You may want to check out fence gate wire kits for this purpose; these usually contain all the parts required in a single package.
One reader wrote to disagree with the advice supplied in this article for hanging fence gates, saying, "The author writes 'If a fence gate is sagging, the problem is usually the supporting posts, the hinge connection or both.' That's incorrect. The usual cause of a 'sagging gate' is the failure or the absence of a correctly installed diagonal brace." On the latter point, said reader elaborates as follows: "Based on all that I have seen and read elsewhere, the correct way to install the diagonal support to prevent sagging is from the bottom hinge side to the top latch side."
However, another reader, Harvey, responded to this by writing: "But, if you look at several other websites, they all seem to state the diagonal support goes from the top hinge side to the bottom latch side."
What You Need
- Spirit level
- Ratchet or open-ended box wrench that fits hexagonal (6-sided) bolts
- Replacement hinge or replacement lag bolts if needed
- Oil or WD-40 for the hinge