[TowerTalk] Re: Concrete base close to house foundation

[dick@pobox.com]

12 SEP, 2000 - 1245 CDT

Hello Jean...

Dealing with frost that goes 48" deep in average winter is certainly a
consideration.  However self-supporting tower foundations for all but
the smallest towers usually go deeper than 48".

A far bigger concern is dealing with side thrust against your basement
wall.  All self-supporting towers are vertical levers with the fulcrum
(balance point) being the surface of the ground.  The wind pressure
exerted on the tower is counter-balanced by the mass of the foundation
below ground.

Over 12 years ago, I was considering the same type of tower foundation
location here.  I abandoned that location for other (political) reasons.
But if I had used it, I was going to dig out my basement wall and attach
three 8 ft. long steel beams horizontally to the wall in order to spread
the side-thrust over a larger area of the wall.

If your basement wall is poured concrete with a lot of reinforcing rod
in it, this might not be necessary.  Same would be true if the tower
is relatively small - less than 45 ft. tall.

I am not an engineer so I can't give you the formulas or hard numbers,
but this is a consideration.  I am sure you will hear more technically
accurate details on this reflector.

FYI, my tower foundation is 4 ft. x 4 ft. x 9 ft. deep and is located
at the opposite end of my house in *UNDISTURBED* soil 6 ft. away from
my basement foundation.  I did not use any wall reinforcement here and
in almost 12 years, there have been no cracks in my basement wall.
Evidently the undisturbed soil "cushion" spreads the load adequately
coupled with the fact that the tower foundation extends 2 feet below
the basement wall foundation.

73 - Dick Isely, W9GIG


--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com