[TowerTalk] Rebar Cage

K7LXC@aol.com K7LXC@aol.com
Thu, 2 Nov 2000 09:31:17 EST


In a message dated 11/1/00 8:33:26 PM Pacific Standard Time, k9huh@icss.net 
writes:

> Am fixing to put the 55 foot free standing crankup back up...Whats the
>  rule of thumb for building the rebar cage to go in the hole....

    My preferred method is to build the four panels on the driveway, 
grass,etc. and then stand them up and tie them together. It'll take 2 guys a 
couple of hours. 

    Since I've got the backhoe there to dig the hole already, I just have him 
lift the rebar cage up and drop it in the hole (it'll weigh 200-300 pounds). 
It doesn't have to be plumb but it can't be touching dirt so put some yard 
pavers under the corners and you should be pretty close. 

    Don't forget that it's illegal to be in a hole deeper than 4-feet without 
adequate shoring so constructing the cage in the hole is a little 
problematic. 

> At the
>  previous QTH I bent it around the uprights but have heard a couple guys
>  say that was a lot of extra work and not necessary just to take straight
>  horizontal pieces and tie them together at the corners...Whats the
>  consensus????

    Getting your rebar supplier to bend them doesn't cost much more but now 
you're trying to assemble a 3-dimensional box instead of putting flat panels 
together. It's more work IMO but you wind up with the same thing

> Also how many Vertical and horizontal pieces would be best,
>  hole is about 4.5 feet squre by 5.5 deep...Also see something in U>S>
>  Tower catolog 3/8 O Tie Bars @ 24" O.C.....Have no idea as to what they
>  are refering to and didn't use it previously just some VERY large
>  washers at the bottom of the anchor bolts.

    You must observe the LXC Prime Directive: "DO what the manufacturer 
says". Have them send you a set of generic plans for your tower - it'll have 
the rebar specs. 

    3/8" rebar is pretty small - it's called #3 rebar. I haven't seen any 
rebar spec'ed for a tower base that was smaller than 1/2" (4/8" = #4 rebar) 
so I'd want to get the *real* information. The rebar are typically spaced 
12-inches on-center also; I've never heard of one 24" OC. A typical spec has 
the rebar cage 6-inches from the edges of the hole so it depends on what the 
size of your hole is/should be. 

    BTW, in many cases the rebar isn't structural; it's there to keep the 
concrete from shrinking and cracking. 

    As far as tying the rebar together, you can either get a roll of tie-wire 
or use the preformed ties. The preformed versions are about 6-inches long and 
have a loop at both ends. You use a tool like a potato sack winder to twist 
them. The roll of tie wire is cheaper but it's more work so that's probably 
the way to go. 

    Once the rebar cage is in the hole, tie your base anchor rods to the 
rebar cage and you'll be ready to pour. 

Cheers,   Steve    K7LXC
Tower Tech - have done dozens of tower bases

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