[TowerTalk] Re: Floating Ground Steel Building?

[Jim Lux]

----- Original Message -----
From: <K7LXC at aol.com>
To: "Jim Lux" <jimlux at earthlink.net>; <kd4e at verizon.net>;
<towertalk at contesting.com>
Sent: Friday, July 02, 2004 3:44 PM
Subject: Re: [TowerTalk] Re: Floating Ground Steel Building?


> In a message dated 7/2/2004 3:14:05 PM Eastern Daylight Time, Jim Lux
<jimlux at earthlink.net> writes:
>
> >The slab itself is grounded, isn't it... This is what UFER ground depend
> >on. There may be a moisture barrier between the slab and some of the
> >ground, but the footings around the edges should be in contact with the
> >soil, and there's a fairly large contact area there.
>
> Umm, actually the rebar is not supposed to touch the soil according to
building codes; the proximity to moisture will cause the rebar to start
rusting and eventually all of the rebar will be compromised and gone.
>
> The problem with a Ufer ground is that the rebar all needs to be bonded to
prevent arcing. Some say brazing is okay, others say no. Just tying them
together isn't good enough.

The Ufer ground in my house (in Southern California, admittedly not a
lightning prone area) is of the copper wire buried in the slab footings
variety.  The slab itself is quite thin, being of the post tension variety.
In PT slab, they have a network of cables which are tensioned after the
concrete has initially set to put the slab under compressive load (huge
compressive load, I might add.. the cables are pretty beefy, and they use a
fairly good sized hydraulic system to tension them).  The cable preload
means that no matter what stresses get transferred to the slab, the concrete
remains in compression.  In any event, there's no rebar to tie to, so they
rely on the 20 or so feet of copper wire embedded in the concrete.
>
> I'm not a concrete expert but I think that the concrete stays moist for
most of its life.
>
> Cheers,
> Steve     K7LXC
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