[TowerTalk] Small free-standing to Bigger free-standing

K7LXC@aol.com K7LXC@aol.com
Wed, 29 Mar 2000 11:26:02 EST

In a message dated 03/29/2000 7:38:17 AM Pacific Standard Time, 
Hank.Lonberg@Harrisgrp.com writes:

> It is perfectly possible to do what you ask. I have done this very thing
>  many times when my clients insist on putting 6 pounds in a pound sack. The
>  trick is in the connecting the new concrete to the existing. What I do is 
>  drill and epoxy rebar dowels into the existing concrete to act as shear
>  connectors between the new and old concrete. Typically they are at 1'-0"
>  centers and project 12 inches out from the existing and are imbedded per
>  manufacture's recommendation for size of bar. This insures that the new
>  foundation acts as a single unit and develops the larger size strength. If
>  you don't do this then under the worst design case, i.e., fully loaded with
>  lateral wind load the foundation would act as two separate pieces and only
>  have the strength of the new one with the old one acting like the soil.
     Wise words. But actually doing this means digging out the existing base 
all the way to the bottom leaving you enough room to manuever and get your 
Hilti and drill bit in there - probably 2 feet. Also one-foot centers means 
nine holes and pieces of rebar PER FACE. As far as I'm concerned, it's not 
much more work to break up and haul off the existing one and then install the 
new base pad that you wanted in the first place. (Lemme see, assuming you've 
got the dirt removed you still gotta cut 36 pieces of rebar, drill 36 holes @ 
5-10 minutes per hole, epoxy them all in then pour a bunch of concrete. I 
don't see that it's worth it.) 

     I'd rent an electric jackhammer and then get some Labor Ready or 
laborers from some place to do the removal work. Eight hours for 2 guys is 
about $200 or less - cheap as far as I'm concerned since I don't want to do 

Cheers,   Steve   K7LXC
Tower Tech

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