Complex situations like that call for professional advice. I would have
hoped that instead of 'my builder and I decided' you could have stated that
the professional engineer's design plans said to do it this way. Then there
would be no question. As a general rule, engineering is done before
construction, damage control is done after.
My one comment... concrete likes water and will absorb and release it
easily, don't waterproof it since that may make water get stuck inside where
it could freeze instead of working its way out.
David Robbins K1TTT
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: Rudy Bakalov [mailto:firstname.lastname@example.org]
> Sent: Friday, June 05, 2009 18:42
> To: email@example.com
> Subject: [TowerTalk] Engineering advice on above ground foundation
> I have a rather complex situation that certainly can benefit from
> the collective wisdom and experience of this reflector.
> My property has a very high water table and as a result my builder and I
> decided to build the tower foundation mostly above ground. Specifically,
> we dug a hole, filled it with compacted gravel that is above the water
> table, covered the gravel with very thick sheets of plastic, and inserted
> 2' styrofoam boards around the base. Then we poured the concrete. As a
> result, only about 1.5' of the foundation is below ground, 3.5' are above.
> The overall dimensions are 10' x 10' x 5'.
> Now I wonder what are the additional engineering issues we need to address
> to make sure the foundation will last and the 90' AN Wireless tower will
> stay up. Currently, we have identified the following next steps:
> 1) Waterproof the concrete using silica based solutions, such as Penetron,
> Xypex, etc. as permanent solution against water getting into the
> foundation2) Add extra waterproofing using tar/asphalt-like solutions to
> make sure we have extra protection should cracks emerge3) Add styrofoam
> boards to prevent against freezing (it gets as cold as -25F in Ontario)4)
> Backfill around the structure to create a mound that takes the rain and
> melting snow water away from the concrete. I have also proposed we layer
> more plastic sheets about a foot below the mound surface to make sure no
> water gets near the foundation
> Any further comments and suggestions will be greatly appreciated.
> Rudy N2WQ
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