[TowerTalk] Rebar Cage Question

[jimlux]

Dr M J DiGirolamo wrote:
> Don,
> 
>  
> 
>    I built my cage from "weld quality rebar" and it was welded by a friend.

<snip>


   I wanted to employ a Ufer ground and that calls for a welded
> cage.  



Actually, Ufer grounds (Concrete Encased Grounding Electrodes, in 
code-speak) don't require welded rebar, even if you're using the bar as 
the conductor (at least in the 2005 NEC)

Art 250.50(A)(3) says: 20 feet of AWG 4 (or larger) bare copper or steel 
reinforcing bar at least 1/2" in diameter. And.. "Reinforcing bars shall 
be permitted ot be bonded together by the usual steel tie wires or other 
effective means"

This is one of those sort of clunky areas, I have to confess.  It would 
technically be ok to have a series of 1 foot stubs, wired together, to 
make up the 20 feet.  But nobody would claim that this is as good as a 
single 20 foot chunk.  I can't find it now, but there is some research 
that did show that 2 overlapped >10foot pieces wired together were as 
good as a single 20 foot piece.



Your engineer or local jurisdiction may require welded rebar for this 
use, of course.  The NEC is just a minimum standard.

Jim