Generally you want to the bottom of the tower hole into "undisturbed
earth". If you have a basement, the original basement excavation may
have been farther out than 3'. The other concern is that a tower base
close to a basement wall will place pressure on the basement wall if it
is too close. Too close is variable depending on soil conditions and how
big/deep a tower foundation you have.
My general rule of thumb is 1.5 times the foundation depth from the edge
of the tower foundation to the basement wall, unless you run the tower
foundation well below the basement foundation or house bracket the tower
rigidly to the house.
If you only have footings - i.e. no basement or crawlspace excavation -
then no problem.
You might want to talk to a local contractor or engineer who is familiar
with the soils and basements in your area.
de n0yvy steve
Lee Hallin wrote:
> I am in the process of making a "plot plan" (something the city requires) in
> preparation, I hope, to getting a building permit for a tower (50'
> self-supporting crankup). One of the things I have to figure out (and
> indicate) is where the tower base will be relative to everything else on the
> lot. I am putting the tower centered along the back of my house. The base
> is supposed to be 7'D x 3.5' x 3.5'. I want the base to be as close to the
> house as possible.
> I want to make SURE that I don't dig close enough to the house so as to
> "under mine" (dirt fall into the hole from the foundation side of the
> hole) the foundation. The area where I will be digging is currently under
> a concrete patio which extends (and has for 8 years) from the foundation
> out (toward the backyard) about 8 feet.
> My idea is to leave a 3 foot gap between the foundation and the tower base.
> Does this seem far enough away from the foundation? I plan to start digging
> in June; give or take.
> Comments? TIA
> 73, Lee WB7SND (ex XR0Z)
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