There are three possible types of foundations called for in the Rohn specs:
pad (rectangular box with minimal rebar), pier and pad, drill and bell. A
big square box obviously takes the most cement but is also easiest to dig
and doesn't require a soil analysis. The other foundation types assume a
4000 PSF soil. An 8N base using a drill and bell requires 6.5 cu yards; a
pad requires 27.3 cu yards. I think a house foundation company could easily
provide the rebar cage for the pier foundation types (pier/pad, drill/bell).
The advantage that most fail to consider is that maintaining a guyed tower
requires far more effort in terms of reoccurring maintenance. The
probability of a guyed tower falling down is many, many orders of magnitude
greater. On the other side of the equation, a self supporting tower should
have a soil analysis done which also might reduce the concrete requirements.
I had a soil analysis for the house construction so it wasn't a delta cost.
'Good' soil would require less cement but if the 4000 PSF requirement is met
or exceeded, but I believe in going with the Rohn specs which would possibly
avoid an engineering analysis. I've never heard of a self supporting tower
falling. We've all heard of deaths resulting from guy wire failures. In some
cases the failures have been induced by operator error. I prefer to climb a
self supporting tower and have reservations in climbing a guyed tower that I
personally didn't maintain. I have no experience with guyed towers but how
long can the guy wires last without having to be replaced? I have to
replace my long wire antennas about every three - four years. In the last
few months, there have been articles (QST??) on guy wire support maintenance
failures. Erecting beams becomes far more difficult with guy wires in
your way. I've had my SSV tower for 27 years and I've had do nothing -
absolutely nothing. I look at everything on my trips up and down but I have
never had to do anything once it was erected. I don't think the XYL would
like guy wire/supports in her gardens and they hurt when you walk into the
wires. The story I tell is that 'we' purchased a 1/2 acre lot and then the
XYL designed a 1/2 house for the 1/2 acre lot which forced me into a self
supporting tower. I find that all of the great decisions I've made in my
lifetime, hardly any were made by me!! Ken K5RG
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