Why Wooden Gates Begin to Sag

A timber gate lives outdoors, so it moves. In a British garden it swells in wet winters, shrinks in dry summers, and takes the brunt of wind, rain and occasional frost. Over time, that constant movement works hinges loose, opens joints, and lets the gate drop on its latch side. The result is familiar: the gate drags on the ground, catches on the post, and needs a shoulder to close. Left alone, a sagging gate strains its hinges, splits its frame and can pull the post out of line. The good news is that most sagging gates can be repaired in an afternoon with basic tools and a little patience.

Diagnose the Problem Before You Start

Before tightening anything, find out what has actually moved. Open and close the gate slowly and watch where it binds. Check the gap between the gate and the post at the top and bottom. If the gap is wider at the top on the latch side, the gate has dropped. Run a spirit level against the hanging post. If the post is plumb but the gate is not, the problem lies with the gate frame, hinges or brace. If the post leans, the repair starts at the post, not the gate.

Also test the gate for racking. Stand at the latch edge and try to lift it gently. A little movement is normal; a lot suggests loose joints or a failed brace. Look for cracked timber, rusty hinges, missing screws and soft, dark patches that signal rot. Prod suspect timber with a screwdriver. If it sinks in easily, cut out the rot and splice in new treated timber before you refit anything.

Tighten and Renew the Hinges

Loose hinges are the most common cause of a dragging gate. Start by tightening every screw. If a screw turns without gripping, the hole is worn. Remove the screw, dip a short length of hardwood dowel or a matchstick in exterior wood glue, tap it into the hole, and snap it flush. Then refit the screw. For heavier gates, upgrade to longer screws or galvanised coach bolts. Check that the hinge pins are not worn or bent. A bent hinge will never sit true, so replace it with a like-for-like galvanised hinge.

If the gate has dropped only slightly, you can sometimes pack the bottom hinge out from the post with a thin hardwood or plastic shim. This lifts the latch side and restores clearance. Do not overdo it: a few millimetres can make a surprising difference. Finish by putting a drop of light oil or silicone spray on the hinge pins so they move freely.

Repair or Replace the Diagonal Brace

The diagonal brace is the gate’s backbone. On a typical ledged and braced gate it runs from the bottom of the hanging stile up to the top of the latch stile. If that brace is loose, cracked or missing, the gate will rack and sag. Tighten any loose fixings first. If the brace is split or rotten, cut it out and make a new one from pressure-treated timber. Measure carefully, cut the ends at the correct angle, and pre-drill to avoid splitting. Fix it with galvanised screws or coach bolts, and use two fixings at each end.

If your gate has no brace, adding one is one of the best repairs you can make. Choose a piece of treated timber about 75mm x 50mm for a standard garden gate, or heavier for a wide driveway gate. Fit it snugly and treat all cut ends with preservative. A well-fitted brace turns a floppy gate back into a rigid one.

Adjusting and Re-setting the Gate Posts

If the hanging post has moved, the gate will never close properly. Check it with a spirit level in two directions. A post that is slightly out of plumb can sometimes be pulled back with a fence post repair spur or a metal post support, but a badly leaning or rotten post should be replaced. Dig out the old post, check the hole for drainage, and set the new post at least 600mm into the ground in concrete. Slope the concrete away from the post so water runs off. Leave it to cure fully before hanging the gate.

For a gate that simply sits too low, you can also adjust the hinges on the gate itself. Sometimes moving a hinge 10mm up or down, or fitting a thicker hinge, gives the clearance you need. Always check the gate swings freely before tightening the final bolts.

Weatherproofing and Routine Care

Once the gate is hanging true, protect your work. Treat any bare timber with a good quality wood preservative, and pay special attention to end grain, the top edge and the bottom edge. A coat of exterior wood stain, paint or oil will slow down the movement that caused the sag in the first place. Keep the gate at least 50mm clear of the ground so it does not soak up moisture.

• Check hinge screws and oil the pins each spring and autumn.
• Clear soil and debris from under the gate so it keeps its 50mm clearance.
• Re-treat any bare patches, especially the bottom edge and end grain.
• After high winds, open and close the gate to check for new movement.

A five-minute inspection each spring and autumn will keep your gate closing with a satisfying click for years.