Contractor Talk - Professional Construction and Remodeling Forum banner

Ideas to form a tapered (conical) concrete base for a flagpole?

297 Views 8 Replies 9 Participants Last post by  NYCB
Hello Gents, mind if I pick your brains a bit as I'm kindly seeking suggestions on how to form a tapered/conical shape for a concrete base at the bottom of a new flagpole. Have done my fair share of concrete but my mind's coming up cloudy on this one. I thought about getting my hands on some aluminum coil stock in as wide a roll I can find and simply forming a square base and then drop the pre-formed sheet metal inside the square formwork (with supporting wedges between the standard forms and the conical coil). But something tells me I'm over-complicating it.

It will be buried in the end, with only the top face exposed so I know it doesn't really matter and I could just use a sonotube but after seeing this detail I still would like to know how it could/should be done. We're getting near a lot of architectural concrete over the last few years -- We like pipe and dirt better, but more and more the GC's like to award entire site developments to one subcontractor, basically the "civil GC" as opposed to dealing with a half dozen different subs for the sitework... I suppose we have to ride the waves that come our way.

Thanks in advance!
PS - I've attached the detail (and colored the concrete base for clarity... also I would not want to have it made in precast if it happens to come up.

Rectangle Font Parallel Slope Schematic


See less See more
1 - 9 of 9 Posts
Why would you have a tapered concrete base with the narrow part down? Seems like that would make it easier for frost heaves to force it out of the ground.
  • Like
Reactions: 1
In actual practice, you just dig the hole that way. If you want the hidden part all pretty, dig the hole and profile it, then use anything to line it.
Rubbermaid garbage can would make a nice form
  • Like
Reactions: 1
Why would you have a tapered concrete base with the narrow part down? Seems like that would make it easier for frost heaves to force it out of the ground.
This. Just asking for problems.
Step one: Find the idiot that drew the plans up and beat the $&!# out of them.
Step two: Get a simple 36" sonotube and use that.
  • Like
Reactions: 3
  • Bore a 24" hole with an auger on skid loader or similar machine.
  • Using a shovel, hand taper the hole 36" dia at top down to 24" dia at bottom as shown.
  • Clean the loose dirt out of the hole.
  • Pin the base plate in place as show on bottom of excavation.
  • Set the foundation sleeve in place and hold it plumb using some wood stakes & framing spanning top of excavation and attached to such.
  • Pour the foundation, using caution to prevent shifting the position of the foundation sleeve.
About as simple of a concrete job as there is. Don't over think it.
Square resists rotation,...should be wider at bottom. Use earthen form to grade, then taper up with plywood or dimensional lumber. That's how I do them anyway...
I would just do it better than that.

Pour a base with your grounding rod in it and C hooks coming out around the outside. Place your sleeve perfect on top of that, then fill the hole with concrete.

If they are fine with an upside down taper, they'll be fine with a straight wall as well.
1 - 9 of 9 Posts