The code for a Ufer attachment to a rebar cage in a foundation is 20' of
conductor against the lowest set of rebar in the bottom outside of the
footing. This can be a 1/2" rebar or a copper wire #4.
http://www.ecmag.com/section/codes-standards/what-ufer-ground
I think that wire tied rebar cages are ok and that welding them is not
required to effectively increase the size of the Ufer.
What else you do I think is dependent on your intent/circumstances. An
elevated house sounds like coastal or flood plain site and if on dry
sand the lightning protection probably needs more than a single column
footing Ufer. More footing area and more parallel connections will
reduce the inductance and far ground resistance. So tying the floor
rebar to vertical conductors in each column seems to me to be a good
idea. If your column footings are tied together with grade beams, all
the better. I assume the columns have at least a 4 vertical rebar cage
and would think those tied well to the footing cage and floor grid would
be adequate connectivity. Whether that is low enough ground resistance
will depend on the soil conditions, so deeply driven ground rods may
also be needed. I suspect most inspectors would want to see those
outside of the footings.
Having several Ufer tie points that exit your floor slab at useful spots
will be appreciated later, unless you can design the perfect "single
point ground" for everything in or out of the house.
Roof grounding sounds easier with vertical wire at each corner all the
way to the footings, perhaps to the #2 to the ground rod lead, all
Cadwelded.
Just my opinions,
Grant KZ1W
On 1/27/2016 3:46 AM, Stan Stockton wrote:
I need some advice regarding what to do in a new construction before concrete
is poured.
It is a small house that will be elevated about 8.5 feet on concrete columns. Floor (8.5
feet above ground) will be concrete slab, exterior walls will be concrete blocks, filled
with concrete. The blocks and slab will, of course have rebar. However, the local
resources to do exothermic welding "may" be limited or unavailable. Roof will
be standing seam aluminum roof. Radio will be located in the house 8.5 feet above ground
against an outside wall.
I thought perhaps running a heavy wire through the center of concrete blocks
and through a column form to a driven ground rod at bottom of the hole for
column would be good enough. Looking for confirmation of whether that's good,
and if so, what would be better and best?
Not wanting to spend a lot of money but do want to do something before the
concrete is poured.
Thanks... Stan, K5GO
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