[TowerTalk] UFER Ground

[Patrick Greenlee]

Stan, seems like you are flood adverse.  Are there cast beams or what 
under the block  walls to carry the load into the columns/piers.  The 
Ufer opportunity is of course the part of the piers extending below the 
surface.  Depending on the area of the slab floor, the rebar in the 
floor might make a decent counterpoise if interconnected by low 
resistance means.  This would not be just standard wire ties that hold 
rebar in place for a pour.

Rebar comes in more than one type.  Typical rebar is not intended to be 
welded and if welded might break up under stress depending on the 
location of the weld. Weldable rebar is, of course, OK to weld.  You can 
weld the non-weld type rebar if you do it in "non-structural" places, 
e.g. at the edges of the slab where the rebar runs past the second piece 
of rebar to which it would normally be tied.

The better approach is to use weldable rebar and at least tack weld all 
the rebar in the slab where two or more pieces touch. The rebar in the 
piers/columns should be welded to the horizontal rebar in the slab.  
This will give you a combination Ufer ground and counterpoise.  If it 
were me I would tie the slab's rebar into the rebar in the walls and 
also ensure that the vertical and horizontal rebar in the walls was 
tacked for good electrical connection.

Typical construction practice is to NOT put rebar vertically in every 
cell of the blocks and similarly all cells are not grouted. In your case 
along with the 100% grouting of your block walls it would be good to 
have rebar in all the cells.  With "standard" 8x8x16 blocks in a running 
bond beam pattern if you put rebar horizontally in every course and 
vertically in every cell you will have a grid of conductors (rebar) on 8 
inch centers.  Walls like this will add considerably to the counterpoise 
effect.  The more counterpoise you have the less important RF ground 
becomes. Electrical safety and lightning ground is still a consideration.

With the rebar in your floor and walls tied to the aluminum roof you 
should get a good counterpoise effect and perhaps some shielding from 
external electrical noise.  This is "flow of consciousness off the top 
of my head advice" and may not be perfect.  Soon the experts will weigh 
in and correct any errors.

Patrick        NJ5G

On 1/27/2016 5:46 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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