Wind speeds, post sizes and hole size and depth for a 4'x8' panel ground sign

the post size, yes that seems overkill.
depth, no that is on par with what we do

 

Ya hafta be ready for those freak conditions. Just like our flood insurance. We're in a 500 year plan and our neighbor to the back of us, who is only 6 inches lower in elevation than us, is in a 100 year plan. Their insurance is super high compared to ours.

Are those holes to be back-filled or filled with concrete ??

 

at least they don't wanted a engineer stamped drawing

 

2x3 hole is insane! The sign is no taller than some privacy fences.

 

Not sure why you'd need a concrete base that big for a 4x8 only 3 feet off the ground, nor a 6x6 post. I have a feeling they are builders (which is the situation we have here as well) who have no concept of how signs are done. I don't know what your soil is like, but here we have rocky soil with clay. For a 4x8, we use two 4x4's, each in a 24" deep hole dug with a posthole digger or if we want to be fancy a 12" auger, filled with concrete. Never had one blow or tip over in over 25 years of doing signs.

Seems like you could put a 2'x3' concrete cylinder sitting above ground and the sign wouldn't blow over. And 6x6's for a 4x8 sign will look very heavy visually.

 

Just figured out where they got 24x36 for the hole size from and the requirement for 6x6's. It's the minimum size hole you can do on this calculator, which also tells you that a 4x4 is undersized unless your sign is 4x7 or smaller if it's pressure treated fir #2. It does allow it if it's pressure treated #2 Southern Yellow Pine: https://www.engineeringexpress.com/sign-post-footing-calculator-2/

 

It does seem excessive but the 7' above grade probably makes them think 6x6 dug in with 2x3 footer seems right to them.
Unless your putting concrete in the smaller diameter hole would seem to work better. That's a lot of bags of cement to load up in the truck, #2 6x6 and 3/4" is a pretty heavy sign.
Don't you get San Andreas winds or Santa Ana winds in CA?
You know the old saying "you can't fight City Hall".

 

My god, if you do it in open field, you'd need a 42in hole!

 

totally misread that original post about the hole diameter.
yeah that is total overkill.

 

Well if the city permit office wants you to dig a large hole with 6x6 posts and you know the “same bonehead” gave you a rough time on the sheer strength of an adhesive. Sounds like you are going to be getting a lot of exercise digging and lifting 60 lb bags of concrete.

 

Post does seem a bit much although here in Michigan we are required to go 42" on the holes. In lieu of concrete, we use pea gravel to set posts

 

Yes, depth of hole depends greatly on depth of the frost line. Otherwise when it freezes it will push the sign up out of the ground.

It's funny, though, how these builder types have no concept of what is really holding the sign up straight and keeping it there. When I first started in the sign business here, sometimes when we put in a post for a sign we didn't use concrete at all. We used packed dirt. Had a vertical tamping rod and you'd put a shovelful of dirt in the hole and pack it down hard, put another shovelful in, pack it, and so on until the hole was filled. Those posts were in the ground! Never had one tip over. But I've seen plenty of signs where they augered a hole, put a sonotube in and filled it with concrete, but didn't take care to pack the dirt in. And a week later the sign tipped over in a mild wind.

For that matter, when we've put up flagpoles, they don't go in concrete at all. They go in sand inside a PVC pipe that is set in the ground.

 

I just like a happy ending.

Ahh...... how do they check if your hole is deep enough ?? Do they come out and inspect it before you can pour ??