My gut feeling is that your 90,000lb 11' x 11' base, sitting on top of
the ground, is enough to hold up your 90' tower, if the concrete doesn't
break, and you don't mind the tower shifting a bit due to frost.
You should have had it engineered, and my gut feeling may be wrong (I'll
leave it to the engineers to due the math), but there you go...
Steve K8LX
Rudy Bakalov wrote:
> I really appreciate all the feedback my post has generated. I think
> it will be helpful to add some further background.
>
> Under normal circumstances I would not trust a builder, but I have
> known this guy for a while and, more importantly, he builds
> foundations for Rogers Wireless in Ontario. I felt that his
> experience with what he does for commercial installations is somewhat
> relevant.
>
> His comment was that although we can pour concrete into water, we
> don't really know too much about the soil below as the water is there
> year around and the soil is very sandy. Thus, the decision to have 2
> feet of compacted gravel below the base. We also chose gravel
> because of its heaving resistance.
>
> The original foundation specs call for a base of 9 x 9 x 5. Instead,
> we built the foundation 11 x 11 x 5, which is close to the specs for
> the 120' tower, and using rebar specified for the 120' tower.
>
> Right now there is no tower on the foundation and won't be one until
> I am confident we have addressed major concerns. Per my original
> post, we have identified the combination of water + freezing as #1
> concern, which we contemplate addressing through drainage,
> waterproofing, lots of insulation, and the mound 15' around the base.
>
>
> Looking back, I realize I should have hired an engineer. But I also
> believe that we can build a solid structure now before the tower goes
> up.
>
> Again, thank you all for the tough but helpful feedback.
>
> Rudy N2WQ
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