[TowerTalk] Tower Foundation (was Concrete Prices)

[Jim Lux]

On 1/2/14 7:41 PM, W7ZZ wrote:
> I'll add my experience, for what it may be worth. A number of years ago,
> I purchased two new AN Wireless freestanding towers, an HD70 and a
> LD60.  The HD70 requires a foundation that is 10'x10'x5' and the 60
> footer requires a foundation 7x7x5.  I had the holes dug by my
> landscaping contractor (the house was a custom and was under
> construction at the time).  However, by the time I started getting the
> bids more than a year later, one hole had sloughed a bit and so some of
> the bidders put in some amount for excavation work.
>
> Bids for whatever excavation work needed tobe done, fabricating the
> rebar cage, hiring the concrete pump truck or line pumper (the holes are
> not otherwise accessible due to their location), the concrete and the
> labor to do the job ranged from a low of $9,000 or so to a high of
> $16,000, I think it was (gee, I didn't keep a copy of that one). One
> contractor was kind enough to explain why:  The pump truck or line
> pumper was $1,000 (every contractor told me that; one had his own line
> pumper so that cost was built in); depending on when I got the bid (this
> went on over several years), the cost of the concrete was $85-110/yard
> (at the time, I was told there was a shortage of concretedue to some
> massive dam construction going on in China, sucking it all up);

yeah, three gorges dam..   kind of like Hoover/Boulder Dam on a larger 
scale.. Amazing to think of a single construction project having an 
impact on the global supply of cement.

> approximately one tonof rebar would be needed for the two foundation
> rebar cages. The contractor's men would have to carry that rebar from
> the front of the house, where it would be dropped off by the fabricator,
> to the two holes, a distance of 100 feet or so for the big tower and 300

That's a huge bump in labor.. schlepping the rebar by hand is a huge 
amount of work.  Probably not to bad if you're doing it yourself and 
dragging one or two bars a day for a month.

> feet or so for the smaller. Labor in each case turned out to be about
> 1/3 of the bid or less and every contractor told me it was a several day
> job.  Every contractor expressed concern about the need for the buried
> tower stub to be perfectly level (so that, when attached to it, the
> tower wouldn't lean).

This is why commercial installations of traffic lights, signs, etc. have 
a bunch of big threaded bolts sticking up, and you run the nuts up and 
down to make a level surface, install the above ground part, and install 
the top nuts.

I don't know if this is a viable strategy for ham towers with 3 
relatively small diameter bolts.  In this approach, the bolt part above 
ground takes a fair compression load, and you need to make sure it's not 
going to buckle.  The street lights, traffic signal kind of 
installations around here have 8 bolts that are 1" plus in diameter in a 
12-18" circle.




   One potential bidder told me after eyeballing the
> site, seeing the foundation plans, etc., that he didn't want the job.
>
> The moral of the story is that,at least for a freestanding tower
> designed for big wind loads, the cost of the tower is just the tip of
> the iceberg.  The foundation work and the boom truck needed to get the
> towers up in the air is a major expense.  I've lived in the house for 5
> 1/2 years now.  My towers consist of two very large holes in my back yard.
>