How to build a strong, long-lasting wooden driveway gate

[BDe]

Hi everyone!

I'm looking for plans and/or tips on the best construction methods for building a wood privacy driveway gate that will be 12' wide and single swing. I will be using redwood fencing to match the rest of my fencing. Thanks for your help.

[Jay Boutwell]

Bde, looks like you will have a pretty heavy gate swinging it on a single 12 foot span.  If you do this I would suggest using at least 2x6" material for the frame work and joinery something like mortise and tendon and polyurethane glue.   Lap joinery is a little weak for this type of construction as is the pocket screw method and most other joints.

Might even think about incorporating some steel into the frame work as well.  You will need to use some carrier wheel at the latch side of the gate and maybe even the use of two to carry the weight.  Cross bracing of the frame with at least tension cables will also be my suggestion.  Good luck with this project as it does sound like a challenge.  I will be looking forward to seeing your final project.

[BDe]

Thanks for the info, Jay. I've seen many different methods of building large gates from a single diagonal brace to placing a vertical brace at 6' and then placing multiple diagonal braces creating equilateral triangles on each half wherever a 90 degree angle occurs in the main frame.

[Ken Darga]

BDe,

An alternate construction approach:

metal fencing tubing, (galvanized steel or alum), for the gate frame, and attach the cedar fence boards (5/8 x 6), to both sides, of the tubing.

The gate frame will require a hortizontal member, at top and bottom, a verticle member at each end, and a verticle support member spaced a 4ft part, secured to the horizontal members.  Fasten joined members with threaded bolts and nuts.  Mortises (recesses) can be put into the back-side of the boards, over the bolt heads and nuts, to make a flush fit. 

This construction would be lighter and easier to handle, over wood timbers, for the frame work.

An 8" dia log, anchored 4ft in the earth, located on the ends of the gate.

(Suggest a treated utility power-line type pole).

Over time, a heavy wood gate 12ft long, will sag, without an adequate support member (wheel), on the opp end of the pivot.

An 8'' wheel will be needed for smooth opening and closing operation on rough (gravel) ground, or a 6" on paved platform. 

 

Sounds like a fun build.

[Russ Haynes]

Three ways for a gate to sag:

(1)  The posts to which the gate is hung are insufficient for carrying the weight of the gate or aren't anchored in the ground properly to prevent them from tilting over time.  A 12' long gate is going to exert some serious downward force at the unsupported end of the gate, and the longer the lever, the less force is required to move whatever is at the opposite end of the lever -- in this instance the post.  Your post needs to get exponentially stronger as the gate gets longer.  For a 12' gate that stands 4' high, I would use 10" x 10" x 10' posts, anchored in post holes six feet deep and at least 3' in diameter, then filled with the most durable concrete I could find, including a polymer product of your choice to prevent cracking.  If I was making a ridiculously heavy gate, I would probably double up the posts on theside holding up the gate, putting two posts on the hinge side, about a foot apart so they could hold up the gate together.

(2) The horizontal supports are not adequately attached to the posts.  Hardware is the most common point of gate breakdown, either the screws/bolts attaching the gate to the post come out, loosen, etc.  Or, the hinges bend or break.  There are gate hinges rated to 1,000 per pair.  They'll cost you around $75 per pair.  But you need to anchor them in the posts so that they won't loosen or come out, or dig into the wood due to the force being exerted on them.  You could mount a steel plate to the post, sort of like a big washer to distribute the force across the post, then lag screw the hinge into the post through the plate.  But you'll need to pre-drill your holes in the plate on your drill press first.

(3) The gate itself is not structurally sound.  Either the horizontal members warp or aren't strong enough to carry the load, or the weight of the gate eventually pulls the top horizontal member away from the hinge, turning the whole thing into a big parrallelogram.  Diagonal bracing is good, just make sure it runs from the unsupported top corner (furthest from the hinge side) down to the bottom hinge.  The closer that diagonal terminates to the bottom hinge, the better.

 

I think I would probably build two six-foot gates, anchor them in ridiculously large posts, then have them meet in the middle.  The 12' would be nice, but it's gonna be a b**** to move and install.  Just make sure you have a good laser set up to get the height and position of your posts right -- once they're in, they aren't moving without a backhoe.  I think 2 x 10 standing on the long edge would provide enough vertical strength and plenty of surface to attach the hinges to.  I might use steel plates on the 2 x 10s where the hinges attach to distribute that force along the 2 x 10 also -- if it cracks on the hinge side, you're done.  For the verticals and the diagonal, I think 2 x 6 would probably do.  Joinery?  I agree on the M&T joints, but would probably add either pins or wedges to secure the tenons in the mortise.  Most likely pins made of 3/8" dowels.

 

Good luck!

[BDe]

Unfortunately, I can't use any wheels as my gate will swing to a downhill slope that will end up being about 3' from the bottom of the gate to the ground when the gate is opened to less than 110 degrees. I have an 8" x 6" x 10' pressure treated post with appr. 4' anchored to a concrete retaining wall to hold the gate. Does that sound sufficient?

[Rick]

Take the total weight of the gate times 6 feet which is your overturning moment, and determine if the supporting wall and hardware will prevent the gate from sagging.  Without a structural engineer looking at drawings, no one has any way to know.

[Ken Darga]

BDe,

Check with a local supplier of fence and gate building materials,

they can be helpful, and guide you in the right direction.

[Ken Darga]

Tubular metal gate with treated utility support poles.

[BDe]

Thanks for all the tips and photos! Got some work to do.

[Rick]

Now that post is adequate!

Even has a solar powered opener, so that you never have guests on cloudy days!

[Ken Darga]

Rick,

That's a treated utility post.

The hinge pins, are bolted ''thru'' the posts---large plates, washers and nuts on the back side.

(1" bolt size).

(Lag bolts are not adequate, for this application---bolt-thru is more secure).

The "L" bolts allow easy removal of the gate---just lift "UP" and off.

The solar panel charges the batteries.

The opener operates on cloudy days and during dark hours.

[Ken Darga]

BDe,

Strength fo the concrete wall depends on how it is constructed:

a. footing depth into the soil ,

b. foundation thickness , and 

c. does the wall contain rebar ?

Inadequate foundation depth, thickness of the wall, and lack of reinforcing rods (rebar) will result in the wall collapsing.  

Consult with local applicable construction codes---under "foundation construction" and "retaining walls".

If your going to use your 6x8 timber, I'd suggest placing your timber in a hole, 4ft deep min, and surrounded by a poured concrete footing, 18'' dia min footing, achored in the earth.

I wouldn't rely on the wall supporting the post.

The gate post will be subjected to a tortional load on the post---weight of gate x length = (could equal thousands of ft lbs of force).

Your gate construction is more than just merely putting up a mail box post.

BDe said:

Unfortunately, I can't use any wheels as my gate will swing to a downhill slope that will end up being about 3' from the bottom of the gate to the ground when the gate is opened to less than 110 degrees. I have an 8" x 6" x 10' pressure treated post with appr. 4' anchored to a concrete retaining wall to hold the gate. Does that sound sufficient?