Connecting 4x4 aluminum posts to concrete

[PatriotWorks]

Looking for a sturdy and attractive way to connect aluminum sign posts to concrete pad or sidewalk.

In another lifetime, I had a concrete pumping business. My experience may qualify for an answer. Concrete works exceptionally well in compression, little else. I made some 6mm signs for a town near me. They vibrated in two shaped steel posts for each sign, don't remember of they were galvanized of stainless....but they were like your typical stop sign posts with holes their entire length. Strong as can be. Stainless hardware. They've stood the test of time. I know bolting into a sidewalk seems skookum but it isn't...particularly when the wind blows. Concrete in tension is not long for this world. Core drill big enough for the sign posts, or miss the sidewalk altogether....they pound down about 4' or better.

 

[Texas_Signmaker]

https://youtube.com/playlist?list=PLTZM4MrZKfW90PdaBFt70BLTbz1bTF6Mn

 

[netsol]

Those anchors and all have engineered spec for tensile and shear but they don't account for the lateral back and forth movement from wind which can jar them loose. That's what the engineer can model. if it was 3 or 4 legs, I wouldn't worry so much. With the building footers here, I am pretty sure they use anchors with a 90 in them which is embedded in the footer to keep that from happening. At a minimum they'd be j-bolts but same idea.

3 points determine a plane

Well damnit, now I gotta go mount something out back and wait for it to fail. Great points, now ya have me wondering about water penetration and freezing too.

One thing to add, when setting threaded rod or j bolts, and you've f*cked up alignment because your template was off or two thin, a long piece of pipe will bend the rods much faster and with much less risk of screwing up the threads than hitting them with a hammer. I never knew that until some old concrete guy I ran into on site came over to help me out. I thought he was an idiot in overalls when he looked at me hitting the nuts on the rod and told me to stop. Came back with a 6' piece of black pipe, dropped over the bolts, and just moved them whichever way he wanted. Was also a good lesson in tension vs shear strength of metals.

But can we all agree, 2 4x4x.125" aluminum posts are not enough for a 4'x6' sign?

jburton,
I always carry a length of pipe, although my 4 lb sledge is like the american express card "don't leave home without it.

 

[visual800]

Go to a thicker walled aluminum. Put some 1/4" thick plates on bottom and use titan HD concrete screws, best on the market! Get some 1/2" or 5/8" tornado would be hard pressed to take it down

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[Texas_Signmaker]

Problem with what you're trying to do it attach it to a sidewalk that has maybe 4" deep concrete? You're basically installing the sign on a 4" footer. When you dig a deep footer, the force of the earth is what is holding it in place, whereas attaching to the sidewalk means the 4" concrete is what's holding it and that is not enough.

 

[Johnny Best]

Sidewalks sometimes, most of the time, have no screening or rebar in it.

 

[Gino]

Right outside our front door, by the intersection, they put a new ADA corner in last summer. They tore the old stuff out and it broke up like nothing. When they put it back, they poured a ton of cement, but they put the rebar in, along with the screening, but it was only about 4" deep. However, there's a diamond shaped sign out at the corner warning on-coming traffic of the height of the bridge just ahead. Maybe 24" square on it's side. They core-drilled about 40" and cemented a square tube with holes and left about 6" about ground level. Then, they attached about an 8" breakaway and then stuck the sign & post up attached to it. When a wind comes along, it sways and goes back & forth like crazy, That's 4 sq ft. I can only imagine what 24 sq ft would do. 6 times the size. Ya better re-think some of these suggestions.

 

[Scotchbrite]

4" x 4" x 1/4" wall tubes on 12" x 12" x 1" thick baseplates? For a 4' x 6' ACM panel? How strong are the winds where you live? Where I work (& other places I previously worked), we would use 3" x 3" x 1/8" aluminum tubes on 6" x 6" x 3/8" baseplates. Installation would be w/ either ø3/8" wedge anchors or 3/8" threaded rod set in the concrete w/ HILTI epoxy. I've used that setup for over 20 years without any failed installations. Just be sure to fabricate an escutcheon cover to slip over the mounting plate/hardware to lessen the trip hazard. I'm personally not a fan of core-drilling the sidewalk - and most customers aren't either - because it's a lot more expensive to repair if the sign/posts are removed.

The plate size is based on the square tube size, not the size of the sign. The idea being there needs to be enough flange to provide support past the tube. The tables I have are based on 110mph wind with exposure type C. I'm sure people have gotten away with less, I'm just sharing what I have from an engineer based entirely on the 4"x4" tube size as food for thought. And as I mentioned, it's for steel not aluminum. I would tend to think you'd need larger/thicker with aluminum.

 

[Gino]

The plate size is based on the square tube size, not the size of the sign. The idea being there needs to be enough flange to provide support past the tube. The tables I have are based on 110mph wind with exposure type C. I'm sure people have gotten away with less, I'm just sharing what I have from an engineer based entirely on the 4"x4" tube size as food for thought. And as I mentioned, it's for steel not aluminum. I would tend to think you'd need larger/thicker with aluminum.


So, what would your suggestion be for 2pcs. 2.5" square tube be for a 4' x 6' sign in cement about 9' to the top of the sign ??

 

[Scotchbrite]

So, what would your suggestion be for 2pcs. 2.5" square tube be for a 4' x 6' sign in cement about 9' to the top of the sign ??

Unfortunately my tables don't go smaller than 4" sq tube. All of the other larger size tubing requires a plate size that is at a minimum an inch more than twice the tube size, how much more than twice depends on the wall thickness. I would say at least 6" square and if you can go bigger, it will be better.

The 2.5" sq tube is fine as long as it's at least 3/16" wall thickness.

And this is for steel.

Interesting, the footing size for that would be 2'x4.5' for each pole. Which brings back the whole concern of anchoring to a sidewalk slab.

 

[MJ-507]

The solution would need to be engineered. Welding on an appropriate sized base plate with gussets would be the ideal solution. Drill oversized holes into the concrete to accept threaded rod of the appropriate size, install the rod in the holes with epoxy (make a little scrap plywood temporary plate to hold the threaded rod in place while curing), then attach the base plated to the exposed rod (nuts on both sides of the plate to level the sign). I would suggest fabricating a small box to cover the whole affair to both make the base more visible and attractive and to avoid tripping over exposed threaded rod.

Direct buriel of aluminum into concrete is not recommended. Tapcons by themselves will fall out (they seem plenty strong at first but eventually will come loose after the sign rattles around in the wind for a few months). Tapcons are great for vertical surfaces where there is no wind load or movement, but in a leverage situation where the moment of energy is transferred to the base it is asking too much. I have seen dozens of small signs tapcon'd to pavement, and they have all failed.

Note: I have had some success using epoxy with tapcons (on walls only). I have had wonderful success at hospitals, schools, and sports venues with my threaded-rod/epoxy installs (and it is incredibly easy and most important - adjustable), but I could see a situation where if the sign could be leveled with morter or epoxy putty, those oversized LDT anchors may perform adequately used in conjuction with epoxy in the holes. I would worry, however, that the concrete would crack over time (oversized holes filled with epoxy greatly lesson the odds of that happening).

Engineered? My customers would never be willing to pay an additional $250+ to have their 4' x 6' ACM panel on posts sign engineered. The sign in question here is so small that it doesn't even register on the charts I use for a basic determination of post/footing sizes.
I think most of the people on this thread are overthinking what should be a simple sign w/ a simple installation.

 

[MJ-507]

Unfortunately my tables don't go smaller than 4" sq tube. All of the other larger size tubing requires a plate size that is at a minimum an inch more than twice the tube size, how much more than twice depends on the wall thickness. I would say at least 6" square and if you can go bigger, it will be better.

The 2.5" sq tube is fine as long as it's at least 3/16" wall thickness.

And this is for steel.

Interesting, the footing size for that would be 2'x4.5' for each pole. Which brings back the whole concern of anchoring to a sidewalk slab.

2' round x 4.5' deep for each pole? What state are you located in? We are all still talking about a 4' x 6' ACM panel w/ an overall height of 6', yes?
The system we use to determine basic engineering shows it would be sufficient to install a 4' x 8' cabinet @ 12'-0 OAH on one steel pole w/ a 2' x 4.5' footing.

 

[Gino]

2' round x 4.5' deep for each pole? What state are you located in? We are all still talking about a 4' x 6' ACM panel w/ an overall height of 6', yes?
The system we use to determine basic engineering shows it would be sufficient to install a 4' x 8' cabinet @ 12'-0 OAH on one steel pole w/ a 2' x 4.5' footing.

Hey there sparky...................

You only gave 2 dimensions for your pad. Care to let us know what ya left out ??

We did a 3' x 8' double-sided sign about a year ago and they figured we needed 24" wide by 72" long, by 50" deep. They also told us what grade cement to use, the rebar and how to tie it together and then it had to be inspected.... every step of the way. Not to mention, it was only 7' to the tippy-top of this sign. I think your codes are a little behind the times or you're jst making this sh!t up. Why would you wanna purposely mislead someone coming here for help ?? Seems as though you need to get out from behind your desk a little more often.

 

[Scotchbrite]

2' round x 4.5' deep for each pole? What state are you located in? We are all still talking about a 4' x 6' ACM panel w/ an overall height of 6', yes?
The system we use to determine basic engineering shows it would be sufficient to install a 4' x 8' cabinet @ 12'-0 OAH on one steel pole w/ a 2' x 4.5' footing.

It's based on 120mph wind exposure C which comes from the 2012/2015 IBC. My tables would want a 2'x7' footing for a single pole 32sf sign at 12' oah.

I think the most recent 2018 IBC might have bumped the wind speed up to 130mph.

I'm in Northern Colorado. Most municipalities and counties in my area require engineer stamped footings for any freestanding sign that requires a permit. The only concession we were able work out was in the closest city we do most of our work in. They won't require the stamped footings if the sign is under 8ft tall and less than 60sq-ft; if it exceeds any one of those, it has to be stamped.

Gone are the days when we can use our charts and nearly 50 years of experience to spec out a footing. It's been a pretty quick turnaround here in about the last 3 years and trust me, it's cost me a lot of sleep worrying over it. There's definitely been a big cost increase for larger freestanding signs. Unfortunately it hurts the local mom & pop businesses the most. Walmart and McDonalds don't care, because they have thousands of locations and only need the engineering for a limited number of sign types/sizes. I still draw up the footings myself and we have an engineering firm that will review them and tweak as needed; most times my specs are just fine.

Hey there sparky...................

You only gave 2 dimensions for your pad. Care to let us know what ya left out ??

We did a 3' x 8' double-sided sign about a year ago and they figured we needed 24" wide by 72" long, by 50" deep. They also told us what grade cement to use, the rebar and how to tie it together and then it had to be inspected.... every step of the way. Not to mention, it was only 7' to the tippy-top of this sign. I think your codes are a little behind the times or you're jst making this sh!t up. Why would you wanna purposely mislead someone coming here for help ?? Seems as though you need to get out from behind your desk a little more often.

I think he's talking about a direct embedment caisson footing which doesn't have the same rebar requirements as an anchor bolt footing or a slab type footing like you're describing.

 

[Billct2]

"3' x 8' double-sided sign about a year ago and they figured we needed 24" wide by 72" long, by 50" deep. They also told us what grade cement to use, the rebar and how to tie it together and then it had to be inspected.... every step of the way. Not to mention, it was only 7' to the tippy-top of this sign."
Amazing, I don't know how any of the 4x8 signs I've installed with a hole digger and a couple bags of concrete have stayed up for 20 years

 

[Gino]

"3' x 8' double-sided sign about a year ago and they figured we needed 24" wide by 72" long, by 50" deep. They also told us what grade cement to use, the rebar and how to tie it together and then it had to be inspected.... every step of the way. Not to mention, it was only 7' to the tippy-top of this sign."
Amazing, I don't know how any of the 4x8 signs I've installed with a hole digger and a couple bags of concrete have stayed up for 20 years

Ain't that the truth. It's just another pitiful money-making gimmick. Here we are always telling people to go work in a real sign shop and learn the ropes, but they don't let us do our job anymore and they have some lunkhead skinny pimple-faced nerd making these decisions. Go figure.

 

[Notarealsignguy]

Ain't that the truth. It's just another pitiful money-making gimmick. Here we are always telling people to go work in a real sign shop and learn the ropes, but they don't let us do our job anymore and they have some lunkhead skinny pimple-faced nerd making these decisions. Go figure.

You have to justify your job somehow. Where will all those engineers and consultants go to work if they don't have any codes to update? Engineers need jobs too. It's all getting to be ridiculous

 

[Gino]

They can get jobs as elevator operators where it's important to recognize an overloaded set of circumstances at a mere glimpse.

 

[Notarealsignguy]

I think this whole thread illustrates the absolutely different climates (literal and political concerning condes/engineering requirements) as well as attitudes those climates have essentially created. The guy in FL who has watched a house tumble down the road has different opinions vs the guy up north trying to get below the frost line, vs the guy in the boondocks who needs enough of a footing to overcome the swamp.
Then ya got the folks with a sledge hammer after dark.

Take Florida as an example. After hurricane andrew, they changed the wind codes down here and for good reason. The hangup for me is that a category 5 storm is the same today as it was back then. Why have they been continually changing the requirements every couple of years despite there being no other storm of that magnitude since 1992? Its getting to be cost prohibitive to build or make any expansions here. You should see the footer requirements now on metal buildings in addition to all of the other bracing and added purlins required. Our shop was built in 1981 and has been through a few bad storms without issue but now I can't even re-sheet my roof without an engineer signing off and adding all of this extra bracing to bring it to current wind code. It's stupid. I could build 3 of these shops brand new at a normal wind code for the cost of 1 that meets this overbuilt code here. So if we got wiped out once every 30 years, I'd be dead before it even got into my pocket.

 

[Gino]

Perhaps, that's their goal.