How to Build a Fence Gate That Won’t Sag [11 Easy Steps!]

Knowing how to build a fence gate that won’t sag is vital for your DIY fencing project. No other part of the fence gets looked at or used more. Needing to lift the gate to keep it from dragging on the dirt to compensate for sag is a bad look. And more annoying than hemorrhoids!

Hopefully, the following information will help you design and build a gate that will never sag.

Why Wooden Gates Sag

Before building your gate, you should know what problems you will be dealing with when you’re learning how to build a fence gate that won’t sag.

Gravity works on everything. Including your fence gate – doubly so when your kids swing on it. Consider that rectangular or square pieces of construction are inherently unstable. Particularly with little or no bracing. And when supported on only one side.

Wood also dries out, twists, warps, and rots. Gates, and fences, in general, seem low on most people’s maintenance lists. Fence gates quite often take a beating! Gates face getting slammed closed, slammed open, kicked, run into, et cetera.

So, when you build the gate, your best approach might be to assume you will leave it to someone in your will. And we urge you to construct the gate accordingly!

How to Build a Simple Wooden Fence Gate That Won’t Sag

The foundation of a fence gate that won’t sag is the posts. Spend some time doing it – or them – correctly! 

Post Basics

You can build the most skookum gate ever. But it will sag if the anchor is weak. The hinge-side post needs to be solid. At the very least, use a four-by-four.

For gates wider than four feet, I would consider a six-by-six. (Because I am anal – and believe gate adjustments should only be necessary after 6.0 earthquakes.)

• A minimum of one-third of the post length should go into the ground. The six-foot fence requires a nine-foot post. Which means you are probably buying ten feet. Don’t cut the post length off! Dig a deeper hole.
• Dig a roomy hole. Do not try to install a six-by-six into a six-inch hole. There is too little room to provide sufficient concrete or K2 foam support.
• Toss in at least four inches of clean gravel, and set the post in the hole – plumb and square to the gate opening. Build supports, as necessary, to keep the fence post in position while concrete or foam dries. (Even a six-by-six will flex a bit with a four-foot gate hanging on it.)
• Fill the hole with foam or concrete. (Foam ready for gate within 15 minutes. Concrete in 24 hours.) Ensure your concrete or foam is slightly higher than the surrounding dirt and gets formed to slope away from the post.

Note: I had some doubts about the foam fence post-filler. Six years ago, I put up a 300-square-foot patio cover on six-by-six posts using 2K foam. Nothing has moved. Use it. We recommend it, especially if you live in the back of nowhere.

There is an overwhelming temptation to attach your gate to a building wall if the location allows it. Attaching your fence gate to a wall is a good option, provided you follow these guidelines.

• Remove all exterior finishes down to the sheathing – even stucco and cement board. (Diamond blade on an angle grinder. Cuts stucco and rock-like butter.)
• You must attach it to a wall stud. Screwing into three-eighths of an inch OSB or plywood is slightly better than using Sky Hooks. Not much.
• Attach (at least) two two-by-fours to the wall with three-inch deck screws. Paint or stain all four sides and ends before installation.
• Check the wall for plumb. If not, shim as required.
• Use exterior window caulking to seal the two-by-four to the exterior finish. With vinyl or aluminum siding, you will need some J-trim first.

Building the Non-Sagging Wooden Gate

Plan your gate to match the height of the fence. Build your gate 48-inches wide, if at all possible. You might buy a 42-inch riding lawn mower. You might buy a hot tub. Or just because you are sick of skinning your knuckles from taking the wheelbarrow through a narrow gate.

For best results, pick a smooth-level work area big enough to accommodate the gate while under construction. Garage floors, patios, or concrete driveways work wonders.

Material List

The wood used for the gate usually matches your fence. You could also make a statement with something that smashes contrast. Cedar, redwood, pine, and even teak make good-looking and long-lasting gates. Where I live, most construction lumber is spruce. All can build a great and sturdy gate.

You can also consider ACQ or pressure treated wood to resist rot and insects. You should (definitely) use pressure-treated posts! Pressure treatment is helpful if you use concrete for setting them.

Also, consider the following!

Pressure-treated wood may contain arsenic and other poisons. This Massachusetts Department of Environmental Health pamphlet suggests pressure-treated wood safety tips. (I have used it for years and only have a small horn growing out of the middle of my forehead.)

Material for a 48-inch by 72-inch gate:

• Pressure treated four-by-four – two @ 12-feet, one @ six-feet
• Concrete or 2K foam post-hole filler – enough to fill two holes four feet deep
• Two-by-four framing – one @ 12-feet, two @ eight-feet
• One-by-six pickets – 10 @ six-feet
• Gate anti-sag kit
• Gate hinge and latch kit 
• Fasteners – Five-inches by one-quarter-inch lag bolts – 20 pieces, two-inch deck screws – 100 pieces
• Self-adhesive bulb weatherstrip one at six-inches
• Options – three-inch by 72-inch piano hinge, gate closer

How to Put Your Fence Together So It Won’t Sag

Time to look at how to build a fence gate that won’t sag! Putting your fence together is a piece of cake if you have all the tools and materials needed.

And – if you follow the below tips, we bet your gate won’t sag.

We hope this anti-sag procedure helps with how your gate looks. And functions!

Step 1. Install the Posts

Install the two posts 48-inches apart following the recommendations. Install the header with two countersunk lag bolts in each post. Make sure it is level.

Step 2. Cut the Side Pieces

Cut two side pieces from 12-foot two-by-four @ five-feet long.

Step 3. Cut the Top and Bottom Pieces

Cut the top and bottom pieces to 47-inches long.

Step 4. Pre-Drill

Pre-drill and countersink top and bottom two-by-four for two lag bolts on each corner.

Step 5. Bolt the Frame

Bolt the frame together (Corner to corner diagonal measurements should be identical).

Step 6. Position the Frame

Cut a diagonal two-by-four piece. Ensure it fits between the lower hinge corner and the upper strike corner. Don’t try to figure out the angle. Just position the frame on the two-by-four, mark it, cut it, and lag bolt it into place.

Another note! Ensure that all your cuts (except the diagonal) are square. It just works better.

Step 7. Install the Pickets

Install one picket on the hinge side of the frame with two-inch deck screws. Extend it one-quarter-inch past the side of the frame.

Step 8. Attach the Hinges

Attach hinges so that they screw into two-by-four framing. (Throw away whatever cheap screws come with the hinges and use deck screws. You will be much happier.)

Position the gate at the height you want by using blocks to hold it up and attach the hinges to the post.

If all works well and posts are plumb and lined up, the edge of the strike side of the gate should line up with the edge of the strike side post. If it is not exactly where you want it, insert a shim behind one hinge to correct the alignment. (Shim the hinge diagonally opposite the strike side corner you wish to adjust.)

Step 9. Finishing Touches – Install the Lock, Anti-Sag Kit, and Gate Pickets

Install the latch or lock. Then install your gate anti-sag kit onto the gate framing as per directions. (It runs diagonally from the upper hinge area to the loser strike corner.)

Use the anti-sag device and maybe even hinge placement to get the gate as close to perfect as possible. (Remember, it is going into your will.)

Step 10. Install a Gate Stop

Install a one-by-two stop on the strike side gate post for the gate to stop against without over-closing and tearing out hinges.

Step 11. Install a Bulb Weatherstrip

Install the bulb weatherstrip on the one-by-two to prevent gawdawful banging noise if the wind slams the gate shut.

Install all the rest of the gate pickets. Screw them on. (You can use nails, but they will loosen and could pull out.)

Make any final tweaks you think are needed, and your gate is ready for decades of trouble-free use. Here are a couple of final thoughts!

I would use a three-inch piano hinge. More support. More screws. Less wear on the stainless product. Available from Grainger, among others. (three-inch hinges are a little pricey but well worth the cost.)

Just a little tip if you must move a screw a little bit. Remove the screw, pack the hole with a sawdust/wood glue mixture, let dry, and re-drill your pilot hole. Way easier than trying to angle the screw in the old gate hole and hoping it bites.

Here Are a Few More Suggestions and Thoughts for Your Non-Sag Gate

If you plan to finish your gate (paint, stain, oil), consider doing it before building the gate. Applying finish before construction increases longevity by providing a coating on all parts that will never see the light of day again. (Note: No Varathane. It yellows in the sun.)

Consider making the gate posts eight feet high and securing a header across the top to provide more support. 48-inches wide at the bottom should equal 48-inches wide at the top. Ensure it stays plumb, square, and level. The gate should last forever. (Eight-foot high because carrying a six-foot, eight-inch patio door under a six-foot header is problematic.)

We love adding a lattice trellis on the posts and a header for climbing plants like ivy, morning glories, climbing roses, et cetera. It makes for an inviting entrance.

Read More!

• Best Fencing Pliers – The 6 Best Fence Pliers for the Job
• How to Build the Best Fence for Cattle – From Electric to High-Tensile
• How High Should a Chicken Fence Be for Keeping Chickens In and Predators Out?
• Practical Gutter and Downspout Drainage Ideas! Rain Barrels, Cisterns, and More!

Conclusion

Learning how to build a fence gate that won’t sag and then building said gate is a lot of work. It’s even more tricky if you want it to look good – and perform well!

We also think that sagging gates are one of the most unfortunate blunders that new gate and fence builders make.

We hope our fence gate guide helps your fence – and gates perform optimally. Without any annoying sagging action.

Also – if you have tips or questions about how to fix a sagging gate, please comment below!

Thanks again for reading.

Have a great day!

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