Connecting 4x4 aluminum posts to concrete

[Jean Shimp]

Looking for a sturdy and attractive way to connect aluminum sign posts to concrete pad or sidewalk. I have a 4'x6' x 6mm aluminum composite sign, single face, to be installed on two 4"x4"x .125 wall aluminum posts. Top of sign is 6' to grade. We have thought of angle brackets on the back side of the post but that's not very attractive. Also we are thinking of bracing the posts with angle aluminum. We tried to find some kind of ready made base that the post would fit in and connect to the ground. They have them for 4x4 wood posts but those don't fit 4x4 aluminum. Trying to avoid having something custom made. Thanks.

 

[Z SIGNS]

Cut a hole in the concrete. Dig a post hole.

 

[Gino]

What he said. Core it out and put a 38" post into the ground and ya only need 2" or 2.5" posts if ya have an 1/8" wall. If you just put a flange on the bottom, there'll be no strength for that kinda sign surface and will be blown away. Around here, ya need an engineered stamped drawing for such an instal.

 

[Texas_Signmaker]

That's what I was going to suggest. Cut into the concrete and install like normal.

 

[signage]

Cut some .25" plate, weld to the post, anchor with some redhead large tapcons (stainless, not zinc coated). Your plates will need to be somewhat significant for the wind load, but really you are more likely to fold the thin 4x4 tubing than to bust a redhead free.

I wouldn't just trust welding I would add some gussets from plate to pole!

 

[Notarealsignguy]

I could see it pulling wedge anchors out, sidewalks only 4" thick and that sign is a decent size.

 

[Scotchbrite]

For a sign that size, I would want to do what others mentioned and core the sidewalk so you can dig footings. Just remember aluminum directly embedded in concrete will corrode relatively quick. That's why aluminum flagpoles use a sleeve in the footing.

A base plate anchored to the concrete slab seems like a tempting alternative, but I'm not sure how big the plate would need to be. Food for thought, the engineering specs I have for steel say 4" square tube with 1/4" wall should have a 12"x12" plate that's 1" thick and use 5/8" anchor bolts. I'm not sure how that would translate to aluminum.

 

[Gino]

I think some of these methods would be unsightly and unsafe according to where this sign is going. Ya sure don't want people tripping over something along a sidewalk like that. Those kindsa installations belong out and away from pedestrian traffic.

 

[Gino]

Who calls for that crap anymore...... ?? Just go out and dig, dig, dig.

 

[Notarealsignguy]

If it's on the sidewalk, is it possible that you have to use break away type mounts? Aren't there setbacks for ADA or anything else?

 

[Notarealsignguy]

Who calls for that crap anymore...... ?? Just go out and dig, dig, dig.

Yeah no shit, just dig fast enough so that you get a good clean break on whatever you hit.

 

[kcollinsdesign]

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).

 

[Johnny Best]

I do not know how long this sign will be up but you are located in Jacksonville which gets some strong winds during hurricane season, June till November. That size would have to be braced really good or its taking off or bending over. That size would have to be engineered with a concrete base and stronger supports.

 

[Notarealsignguy]

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.

 

[Notarealsignguy]

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.

Put nuts on them first which also protects the threads and if they do booger up a little, when you run the nut off, it cleans them back up. Same with cutting threaded rod which you probably already know.

 

[Notarealsignguy]

Oh yeah, but at the same time I picked up one of these (moving nuts across a 6' length your converting into 2" lengths can be time consuming) and I'll be damned if it doesn't work relatively well. Don't remember it costing this much though...

Amazon.com

Thats a cool little tool. I used to have one of the amigos here cut it all down so doing all that was his problem. We would just bevel the edge with a flap wheel.

 

[Scotchbrite]

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

I was curious about that myself and tried to find engineering data for aluminum square tube but didn't have any luck. If it was steel, a 2.5" pipe would suffice and 2.5" square with 3/16" wall would be overkill, but not sure how that translates to aluminum.

I've never used SignComp sign systems, but maybe a person could figure out what might work by investigating their installation instructions.

 

[Billct2]

How about something like this?

 

[Scotchbrite]

Safe bet with aluminum is doubling down on steel thickness/dimension. Sure its overkill, but more often than not you're doing something you probably shouldn't, might as well overshoot.
Don't forget, they are in FL, so they require hurricane ratings for wind load. Not certain on signs but found where it states structures will need to withstand 165-195 mph gusts. Does that change your calculations any?

It would. Ours are based on a wind speed of 110mph, exposure C.

In general we just stay away from using aluminum posts. In 22 years, I think we've done it once. Luckily we're in an arid climate so painted steel is usually just fine. If a customer was really pushing for it, I would probably use a thin wall aluminum post sleeved over a steel post so the aluminum post would basically just be decorative.

 

[MJ-507]

For a sign that size, I would want to do what others mentioned and core the sidewalk so you can dig footings. Just remember aluminum directly embedded in concrete will corrode relatively quick. That's why aluminum flagpoles use a sleeve in the footing.

A base plate anchored to the concrete slab seems like a tempting alternative, but I'm not sure how big the plate would need to be. Food for thought, the engineering specs I have for steel say 4" square tube with 1/4" wall should have a 12"x12" plate that's 1" thick and use 5/8" anchor bolts. I'm not sure how that would translate to aluminum.

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.