Casting for flagpole?

[Calle Nordström]

Hello,

I have cast for a flagpole. I made a hole of 55cmx55cmx65cm. I used expanding concrete and it took 12 bags, i.e., 300kg.

Now, when I read, I see that you should really dig 100-120cm and have a 40cmx40cm hole.

The question is whether you think my foundation will work? The flagpole is 12m and made of fiberglass, weighing 38kg including the base.

//Calle

 

[AG A]

Unfortunately, I am afraid that the flagpole will topple over.

 

[Marsman80]

It's certainly better to have a deep hole, but what you've done should work as well. It definitely depends a lot on how stable the ground is and how much it blows. I can't imagine it blowing over, but if it starts to lean more and more, it might be time to create a new "foundation". I personally used an earth auger and drilled straight down about 50 cm and then in 3 different directions from there, as it felt more stable than a straight pier. The earth auger was only 22.5 cm in diameter, but my 12 m flagpole stands firmly despite a windy location.

 

[MathiasS]

You have cast a 300kg lump! It's not going to fly away. I didn't even get a meter down before hitting rock. I have a simple casting pipe with concrete, a fraction of what you have, about 45 liters. That flagpole has stood straight for over ten years now.

Start hoisting the flag and see what happens, I think it will work excellently. If it's not okay, it's unlikely anything dramatic will happen.

 

[Calle Nordström]

Thought so too, the weight in the plinth is 80 times the weight of the pole, a flag doesn't have much wind resistance since it constantly turns with the wind. Will have to try and see, not more than having to re-cast if it goes wrong.

Thanks for the reply anyway!

 

[Calle Nordström]

Just wanted to let you know that the base works fine, flagged in a windy situation without moving a millimeter.

 

[Stefan N]

Yes, it will remain standing.

 

[niklasn]

It will probably stay standing, but as a comparison, I can tell you about my sailboat - 5 tons total weight, of which 2.8 in the keel, with the center of gravity approximately 1.40 below the water surface. The mast is about 16m above the water with a slender profile, more streamlined than a flagpole.

In a wind of 7m/s, directly from the side without sails, the boat leans about 15 degrees... So don't underestimate the effect of the wind, especially as the force in a flagpole is at the farthest point from the base.

 

[jvhavshus]

Just wanted to let you know that the foundation works fine, flagged in windy conditions without moving a millimeter.

Hello Calle!

I'm in the same situation as you now, have a hole about 55x55x70cm, that is 70cm deep. My flagpole is identical in dimensions and weight to yours.

How does yours look after all these years? Is there anyone else here who has had the same issue?

 

[MathiasS]

You've cast a 300kg block! It's not going to fly away. I didn't even get a meter down before I hit rock. I have a simple casting tube with concrete, which is a fraction of what you have, about 45 liters. That flagpole has stood upright for over ten years now.

Start flying the flag and see what happens, I think it will work excellently. If it's not okay, nothing dramatic is likely to happen.

Another ten years later, my flagpole is still standing.

 

[Flomi]

Another ten years later, my flag pole is still standing.

Your flag pole?

 

[MathiasS]

Your flagpole?

It looks like that's what I wrote. I have very little statistics on others' flagpoles, it's not something I keep track of.