Quick Answer
Most sagging gates can be fixed without full replacement in 1–3 hours for around $20–$80. The most common cause is loose or worn hinges — tightening, replacing, or repositioning them fixes 80% of sagging gates. A diagonal anti-sag cable kit ($15–$25) adds structural support for wider gates. Full replacement is only needed when the gate timber itself is rotten or the post has failed at the footing.
Why Gates Sag: Root Causes
Understanding why a gate sags determines the right fix. There are five common root causes, each with a different solution.
| Cause | Signs | Fix | DIY Difficulty |
|---|---|---|---|
| Loose hinge screws | Hinges visible but wobbly; screws partially pulled out | Replace screws with longer/wider gauge | Easy — 20 min |
| Stripped screw holes | Screws spin but won’t tighten | Fill holes with timber dowel + glue, re-drill | Easy — 45 min |
| Bent or worn hinge | Hinge plates visibly bent or corroded | Replace hinges entirely | Easy — 1 hour |
| Gate frame out of square (racked) | Gate is square when open but parallelogram-shaped when viewed flat | Anti-sag tension rod or cable kit | Moderate — 1–2 hours |
| Leaning or rotten gate post | Post leans away from gate; post base is soft | Re-set or replace post (see fence post guide) | Hard — half day+ |
Method 1: Fix Loose or Stripped Hinge Screws
This is the most common cause and the simplest fix. Over time, hinge screws — especially in pine or softwood gates — can strip out of the timber as the gate swings repeatedly under its own weight.
What You’ll Need
- 75mm–100mm 10g or 12g stainless steel screws (longer and thicker than original)
- Timber dowel rod (10mm or 12mm diameter) and exterior PVA glue for stripped holes
- Phillips or square-drive screwdriver or drill
- Drill bit matching your dowel diameter
Steps
- Support the gate — prop the gate level using a timber off-cut or car jack under the latch corner before working on the hinges. This takes the weight off the fixings while you work.
- Remove and inspect the hinge screws — unscrew one hinge at a time. If the holes are stripped (screw spins freely), fill them with timber dowel.
- Fill stripped holes — cut a timber dowel to length, coat with exterior PVA glue, hammer flush, and allow to dry (1–2 hours).
- Re-drill pilot holes — drill a pilot hole slightly smaller than your new screw diameter through the dowel fill.
- Reattach with longer screws — drive in 75mm–100mm screws that reach well into the gate post or frame, not just the surface timber.
Method 2: Install an Anti-Sag Gate Cable or Rod
When the gate frame itself has racked (gone out of square due to gravity pulling the unsupported latch corner down), an anti-sag kit adds a diagonal tension member from the bottom latch corner to the top hinge corner, counteracting the sag.
Anti-Sag Cable Kit ($15–$25)
Available at most hardware stores, an anti-sag kit consists of a steel cable with turnbuckle, two corner brackets, and fixings. It takes about 45 minutes to install.
- Measure the diagonal — the cable runs from the bottom latch corner to the top hinge corner (the opposite diagonal to the direction of sag).
- Attach corner brackets — fix the L-brackets at each corner using the supplied screws, drilling pilot holes to avoid splitting the timber.
- Thread the cable and attach turnbuckle — route the cable through both brackets and attach the turnbuckle in the middle.
- Tension the cable — with the gate propped level, use a spanner to tighten the turnbuckle until the cable is taut. The gate should now sit at the correct height.
- Check swing clearance — open and close the gate several times to confirm it clears the ground and latches correctly.
Method 3: Replace the Hinges
If the hinges themselves are bent, corroded, or undersized for the gate’s weight, replacing them is straightforward and costs $20–$60 depending on hinge type and size.
Choosing Replacement Hinges
| Gate Type | Recommended Hinge | Cost per Pair |
|---|---|---|
| Light timber picket gate (under 15kg) | 100mm strap hinge, galvanised | $15–$25 |
| Standard 1.8m timber gate (15–30kg) | 150mm heavy-duty butt hinge or weld-on hinge | $25–$50 |
| Large or heavy hardwood gate (30kg+) | 200mm ball-bearing hinge or heavy-duty weld-on | $40–$80 |
| Colorbond or steel gate | Adjustable gate hinge (weld-on or bolt-on) | $30–$60 |
Always choose hinges rated for at least 1.5x the gate’s actual weight. Gates swing hundreds of times per year — undersized hinges fail faster than the gate itself.
Troubleshooting: Why Is My Gate Still Sagging After Repair?
| Problem | Cause | Fix |
|---|---|---|
| Gate sags again within weeks of repair | Post is leaning or footing has failed | Check post for movement — may need re-setting |
| Gate sits level but still won’t latch | Latch strike plate is misaligned, not the hinges | Reposition the latch strike plate on the post |
| Gate opens fine but sticks when closing | Post has moved or gate has swelled with moisture | Plane the latch edge; check post alignment |
| New screws strip out quickly | Timber at post is rotten or too soft for grip | Replace affected post section or use through-bolts with washers |
| Anti-sag cable stretches and goes slack | Cable kit undersized for gate weight | Upgrade to solid steel anti-sag rod with turnbuckle |
When You Should Replace the Gate Instead
A gate is worth replacing rather than repairing when:
- The frame joints are separating and the timber itself is rotten or crumbling
- Multiple boards are cracked, split, or missing, compromising privacy or security
- The gate is so heavy (particularly old hardwood) that standard hinges and posts cannot support it — replacement with a lighter Colorbond gate makes more sense
- The gate post has failed at the footing and the full post needs replacing — a new post is a natural opportunity to also replace an aged gate
Tips and Gotchas
- Always support the gate before working on hinges — unsupported gates can twist suddenly when screws are removed, and a 20–40kg timber gate falling on fingers is a serious injury risk.
- Use stainless steel screws, not galvanised — in Melbourne’s outdoor environment, standard galvanised screws rust through within 5–8 years, especially near the coast (Frankston, Mornington). Stainless steel costs a little more but lasts indefinitely.
- Three hinges for gates over 1.2m tall — most standard residential gates are hung on two hinges, but a third hinge in the middle reduces racking dramatically, especially on gates over 1.5m tall.
- Check post movement before doing any hinge work — if the post is leaning 10mm or more, fixing the hinges won’t hold. Fix the post first.
- Adjust latch position at the same time — while the gate is level and propped, adjust the latch strike plate to line up correctly with the latch body. This avoids having to repeat the job later.
- Melbourne clay soil heaves posts seasonally — gates that sag in summer and fix themselves in winter (or vice versa) are usually being moved by clay soil expansion and contraction. Consider using a post with a larger diameter concrete footing to reduce seasonal movement.
FAQ
How do I stop my gate from sagging again after I fix it?
Add a third hinge in the middle of the gate if you currently have two, use an anti-sag cable kit for extra diagonal support, and upgrade to 100mm stainless steel screws into the post. Also cap your gate post top to prevent water entering the end grain and rotting the post from within — a rotten post is the most common cause of recurring sag.
Why does my gate sag in summer but not winter in Melbourne?
Melbourne’s clay-heavy soils (particularly in Pakenham, Berwick, Cranbourne, and Narre Warren) expand when wet and shrink when dry. A gate post set in clay can move 10–15mm seasonally, causing the gate to appear to sag in summer when the soil dries and shrinks. The fix is re-setting the post in a larger diameter concrete footing that isolates it from soil movement.
Can I fix a sagging Colorbond gate myself?
Yes — Colorbond gates use adjustable bolt-on hinges that are typically easier to adjust than timber gate hinges. Loosen the hinge bolts, lift the gate to the correct level with a prop, re-tighten the bolts, and check the latch alignment. If the Colorbond gate has sagged because the steel frame has twisted, the frame itself usually needs replacing as Colorbond steel is not weldable at home.
What size screws should I use for gate hinges?
Use minimum 75mm 10g stainless steel screws for light gates, and 100mm 12g stainless steel screws for gates over 20kg. The screw length is the most important factor — short 40–50mm original screws are the number one cause of hinge failure. The screw needs to pass through the hinge plate and at least 50mm into solid timber beyond any surface coating.
Local Melbourne Resources
- Bunnings — Gate Hardware and Hinges (hinges, anti-sag kits, latches)
- Mitre 10 — Fencing and Gate Hardware
- Consumer Affairs Victoria — Fences and Boundaries