Of all the parts that make up a fence, none sees more wear and tear than the gate and its support post. And nothing wears on these specific parts more than gravity. Gravity is constantly pulling gates downward, stressing hinges, loosening fasteners, and coaxing the gate post to lean over. With a metal fence, the gate itself is either welded or bolted together and usually does a good job defying the force of gravity. But if the gate post starts to lean, the whole gate shifts down, and the gate won't close properly.
Wood gates have more vulnerable areas than metal. The screws or bolts holding the hinges can loosen in the wood, and the entire gate structure can fall out of square, due to its own weight. Wood gate posts also can lean, of course, but they're even more likely to rot where they meet the ground, allowing the gate to sag and/or swing in a quirky, jerky motion.
There are relatively quick fixes for a wood gate that has loose hinges or has gone out of square. Repairing a gate post—either wood or metal—is more extensive. It typically requires digging up the post and its concrete footing and reinstalling it (or a new post) in new concrete. Simply trying to shim, brace, or otherwise shore up a leaning post is just a temporary fix and usually isn't worth the time.
What You'll Need
3 Ways to Fix a Sagging Fence Gate and Instructions
Tighten Hinges on a Wood Gate
Total Time: 30 minutes
Material Cost: Between $3 and $10
Hinges on wood gates are mounted with heavy-duty screws or lag screws, but they can lose their grip over time. Instead of moving the hinges to drive into new wood, it is easier and more secure to drill through the old holes and mount the hinges with carriage bolts that run all the way through the gate post and gate. Use galvanized or stainless steel carriage bolts to prevent corrosion, and choose a bolt diameter that will fit through the pre-drilled screw holes in the hinges.
Note: If the square section under the bolt head (a unique feature on carriage bolts) won't fit through the hinges' screw holes, you can use standard bolts instead.
- Remove the hinge fasteners from the gate post and remove the gate.
- Remove the hinges from the gate.
- Choose a drill bit that is the same diameter as the threaded shafts of the carriage bolts. The bolts should fit snugly in the holes.
- Drill holes straight through the gate post, using each of the existing hinge screw holes as a guide. Do the same with the screw holes on the gate.
- Mount the hinges to the gate with carriage bolts, washers, and nuts. Tighten the nuts securely with a socket wrench. In most cases, it's best to insert the bolts from the outside of the gate so that the washers and nuts are on the inside.
- Prop the gate in position and mount the hinges to the gate posts with bolts, washers, and nuts, as with the gate.
Square Up a Sagging Wood Gate
Total Time: 30 minutes
Material Cost: Between $10 and $15
Wood gates always drop down toward the bottom corner opposite the hinges so that the gate is no longer square. Installing an anti-sag gate kit pulls that low corner up and toward the upper hinge to square the gate so it hangs straight. The kit contains metal corner brackets, cable (and cable fittings), and a turnbuckle. Once you've installed the hardware, you simply turn the turnbuckle to pull the gate square. When the gate starts to sag again over time, just give the turnbuckle a few more turns to square it up.
- Install the two corner brackets from an anti-sag kit on the inside of the gate frame, using the provided screws. One bracket goes on the corner nearest the top hinge; the other goes on the diagonally opposed corner, on the bottom corner opposite the bottom hinge.
- Unscrew the turnbuckle so it is fully extended, then hook it onto the upper corner bracket.
- Thread the cable through the turnbuckle and the lower corner bracket as well as any take-up fittings provided. Secure the cable ends as directed by the manufacturer. You may need to create loops and secure the cable ends with cable clamps, tightened with an adjustable wrench and pliers. Pull the cable tight before installing the clamps.
- Tighten the cable, using the take-up fittings (if applicable) to remove as much slack as possible from the cable.
- Turn the turnbuckle to tighten the cable, pulling the gate into square, using an adjustable wrench or pliers. Close the gate to check its fit as you work, tightening the cable until the gate closes properly.
Reset or Replace a Wood or Metal Gate Post
Working Time: 4 hours
Total Time: 8 hours
Material Cost: Between $20 and $40
Resetting or replacing a gate post requires removing the gate, digging up the post and its concrete footing (if there is one), and installing the same post or a new post in fresh concrete. You can reuse a metal post if it is in good condition (and you can remove it from the concrete), but you should always replace a wood post with a new pressure-treated post rated for ground contact. The easiest way to reset the post is to fill the hole with dry, quick-setting concrete mix, then add water. The concrete cures in about 4 hours.
- Remove the gate hinges from the gate post and set the gate aside.
- Disconnect the first fence panel from the gate post, as needed. Shift the panel out of the way, if possible; otherwise, disconnect the panel from the next post and remove the panel entirely.
- Dig out the soil around the gate post to loosen the post or its concrete footing, using a shovel. Remove only as much soil as needed; it's best if the soil around the hole remains intact because it is already compacted and will hold the new concrete footing securely.
- Pull the post and/or footing out of the ground. To reuse a metal post, break up the footing with a sledgehammer and remove the post.
- Use a post-hole digger to enlarge the hole, as needed, so its diameter is at least three times the size of the post (example: for a 4-inch post, dig the hole 12 inches in diameter) and its depth is equal to 1/2 of the above-ground post height, plus 6 inches (example: for a 6-foot fence, dig the hole 3 feet, 6 inches deep). Note: If you're reusing the gate post, adjust the hole depth so the post will be at the original height.
- Add 6 inches of compactible gravel to the hole and tamp it down with a wood fence post or a scrap board.
- Set the new (or reused) post in the hole and position it so it is spaced properly and aligned with the other gate post.
- Secure two perpendicular braces (using scrap boards) to the post, near its middle, using duct tape (for a metal post) or screws (for a wood post). The braces should angle down to the ground at roughly 45 degrees. Drive a wood stake into the ground near the end of each brace.
- Use a level to position the post plumb (perfectly vertical), checking on all sides of the post, then secure the braces to the wood stakes with screws to hold the post in place.
- Fill the hole with quick-setting concrete and add water, as directed by the manufacturer. Let the concrete cure for at least 4 hours, or as directed.
- Remove the braces and reinstall the fence panel and gate. If the new gate post is wood, trim the top of the post, if necessary, to match the original, using a handsaw or reciprocating saw.