Determine post size and mounting a heavy gate

[Bmallen77]

Gotta gate I'm getting real close to hanging and I am really struggling with whether I have chose the correct posts to mount to, and whether my concrete hole to support the post will be deep enough.  I have tried a few post calculators online but can't find enough information to feel confident in my posts. 

The gate is 8' tall, 4' wide, and weighs almost 300 lbs. the post I chose to hang the gate on is a 2"x3" structural tube post with a 1/4" wall thickness. On the other side of the post is a 13" wide side panel also 8' tall that is welded to the same post. That panel additionally weighs about 85lbs. 

My initial plan was to set the posts 30" deep in concrete and hang everything off of the post without tying any tabs or anything into the building. It's a large archway and I'd really like it to be free standing without anything tied to the to the side of the archway to support the post when it's under the load of the gate.  

From what I'm describing and the pictures do you think I'm overdoing/underdoing it? Will that post set 30" deep in concrete be enough to support all that without sag??

You can see in the picture the posts. The left side is where I am talking. The post will have the gate and side panel mounted on the same post together.

[BD1]

What material size / shape steel is the gate and panel made from ? Depending on that , I would use square 3x3 or 4x4 tube or 3'' schedule 40 pipe. Round or square depends on what would look better. As for the depth, 30'' seems fine to me , you shouldn't need to worry about frost in California. 

[Fred Beagle]

You're not overdoing it at all. I've done a lot of gates over the years On a heavy swing gate we use to put what I'd call a landing but it was like a 3'x3' square dug a foot deep and then the posthole  will go right in the center of it and we also "Stake the post too" with several 3/4 tubings about 2' feet long driving into the dirt diagonally up against the post and weld them onto the post when you have the post level. A helper to hold the post level in both directions helps while you do this. But the cement will cover the stakes and you might want to put some rebar in the landing as well. but let the green cement set for a day or two until it's cured and when your hanging a very heavy gate it doesn't hurt to have it slightly out of level so that when it's finally hung the weight of the gate will drop it down to level. Heavy duty barrel hinges with the grease fitting and ball bearing inside the hinge is what I would use for hinges as well. 

I realize the landing might be over kill but for years I was an installer doing this and this is what we would do for monster swing gates that go over drive ways and used an operator. a walk gate maybe not so much.

[ironwolfforgeca]

for my two cent's worth 2x3 is not enough I would do 4" sq tube - 3" min & maybe rebar in tubing & cement

if posts can't handle wt well you'er Done ! I have a friend that does BIG gates often he will weld legs to posts

run I beam across  and bury & cement the hold support frame across to the other post - also rec tube will bend more

than Sq tube

Steve's Welding & Fab

[Bmallen77]

I appreciate all the replies and advice. The gate and side panels are made of 1" solid square bar for the frames and the inner sections of the gate are filled with 3/8"X1" flatbar. There is also some additional weight in copper paneling.In addition to the copper paneling in the side panels, all four open panels of the gate will have copper as well. I added a picture of the unfinished gate so u can get an idea of the weight and distribution of weight.

from the specs I have found on the post, structurally the 2"x3"-1/4" wall thickness tube is plenty adequate to support up to 1000lbs with hardly any deflection depending on where the barrel hinges mount. In addition the post will be taking its load mainly on the 3" side of the tube rather than the 2" side.  My main concern now is the footing. You see all types of stuff out there about a post being at least 1/3 of its total length in the ground. So for my case, the post is sticking out of the ground roughly 90" so that would mean I need a minimum of 30" in the ground. But It doesn't say anything about that post being under a load of a gate. 

I really like the landing idea depending on how compacted the ground I'm digging into will be.  I think that is definitely something worth adding at least for the shear weight of all that concrete down below for weight. 

and your absolutely right ironwolf, obviously if that post is not strong to support all that weight   then I am SOL. I Guess when in doubt, "nuke it out." 

Is there no formula or rule of thumb for a foundation for a gate post? I have seen formulas for column loads, but that is only focusing on down pressure, it's not taking into account a heavy item swinging on it 4' away with all that additional leverage.  

Thanks for the information.

[SmoothBore]

What you've got there, MIGHT work, ... MAYBE.

In my opinion, "might & maybe" is NOT a formula for success.

To be SURE of the quality of the finished job, I'd want 4"x4" posts, ( with at least 1/4" wall thickness ) ... set a minimum of 3' deep, ... and "slush" the hollow posts full of concrete.

( Filling hollow posts with concrete has an amazing "stiffening" effect. )

Tying the posts together, underground, is also a great idea.

While all the above might not be absolutely necessary, ... it doesn't add much material cost or labor, ... and it prevents that nicely constructed gate from becoming a potential disappointment.

If the customer wanted a low-cost POS, they would have bought one at Lowes.

 

[Fred Beagle]

If you stake it and I WOULD STAKE IT! She'll hold. The landing is only something we would use on huge swing gates that goes across drive ways. You may not have that sort of room. And how is it going to look aesthetically as well has to be considered. The other posts had some good ideals as well. By going in 3' foot deep and perhaps tying into the
the stop post under the dirt to make a rigid frame seeing how you don't want to come off the building with anything is something we've done before. Like I said the stakes you drive them off into the side of the hole and drive em deep! Then when the swing pole is level,weld it to the stakes and cover with cement.. Good looking gate by the way ,really nice work I like it!

[BD1]

AWESOME lookin for sure !!!  As for the in ground part, maybe consider bending rebar  like rocketship wings and weld to it. 

[Bmallen77]

I definitely will tie the two posts together with something, I need to check my scrap and figure out what I can come up with. Thanks for all the advice. It's absolutely worth making some adjustments to ensure a great final product. Concrete and rebar are both cheap and worth the insurance.

[Fred Beagle]

[Daniel 1978]

I am looking to hang a 12’ft x 8ft gate. Our estimated weight is around 850lbs. Any suggestions to the pipe size that will support this weight. 

[Charles R. Stevens]

Soil type is a big factor, around here I weld a 15 or 16” rim to the bottom. The side panels will help prevent the posts from leaning in. Some times you have to resort to tall posts and a cross tie

[BsnNFrnt]

I have an 18’X 4’ gate hanging off of this brace. Weight of the gate is around 300#. 
The brace is 4” square tube .25” wall thickness, the bottom of the posts are 48” with a Whole pallet of bag concrete mix poured in the hole. If you have the capability and the room for an H brace - you can hang what ever you want off of this style in my opinion. 

[anvil]

I agree