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RE: Flag-Pole Foundations for light framing

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I don't use rebar if the pole extends through the concrete.  Consider the concrete to be an unreinforced thrust block.
Check the weight of adjacent concrete acting in friction to see if will resist the pole reaction at the surface.
-----Original Message-----
From: Dennis Wish [mailto:dennis.wish(--nospam--at)]
Sent: Wednesday, November 19, 2003 1:03 PM
To: light_framing(--nospam--at); seaint(--nospam--at)
Subject: Flag-Pole Foundations for light framing

I have two Flag-pole foundations designed for the front of a custom home where the forces in each column (lateral force) based on an R of 2.2 is 690-pounds placed at 12’-0” above the top of the foundation. The entry is flatwork which is monolithically placed and is, in my opinion, sufficient to restrain the top of the column. A 18-inch square foundation pier extends up from the flatwork six inches and the foundation is 4’-0” below soil and 30” square. The Column is a TS 6x6x5/16” square tube has approximately 6-inches of flatwork on the two exposed edges of the flatwork (outside edges) and is continuous between columns.


The plan check corrections asked for two things:


  1. The minimum reinforcement for the concrete foundation
  2. The clearance surrounding the columns to show adequate restraint of the flatwork. It is assumed that the area in front of the columns will also be done in either brick/tile or concrete sidewalks with an area abutting the entry flatwork.


Unless the lateral loads were large, I have not in the past provided reinforcement with this much cover around the steel columns. The columns extend through the foundation and are secured to a 12” thick erection pad. The column should be sufficient to handle the moment in the base, and the concrete transfer the bending moment below grade without the need of a cage or vertical rebar. The passive soil pressure should also be sufficient due to the analysis to resist overturning of the columns with such low lateral loading. The erection pad is more than sufficient to support the entry roof dead and live loads.

Am I missing something here? Is there a minimum steel requirement for a flagpole with small lateral loads? Where would I find the information in the 97 UBC that might reference ACI-318 on this issue?


I have always used flatwork as a means to offer restraint against rotation of small lateral load columns. What, if any, is the minimum edge requirements to the edge of the foundation especially since the piers extend above a post hole foundation that is 30-inches square and 48” deep?




Dennis S. Wish P.E.