[TowerTalk] building code questions
kr7x at comcast.net
Wed Feb 1 14:17:06 EST 2006
Pouring against undisturbed earth is quite ok. As long as you have the required reinforcing bar clearance (3" per ACI) pour away.
Pier and pad foundations (spread footings, isolated footings) that are formed allow only the required (by design) amount of concrete to be placed. Their use requires the backfill and compaction to be controlled to develop any needed lateral resistance. If the loading is only vertical such as a guyed tower then the backfill and compaction around the sides of the pad and pier is not as critical. It is the condition of the soil under the pad base that is important.
The padless pier would be ok as long as it is large enough (in plan) to develop the required soil bearing load.
Lonberg Design Group, Ltd.
H.Lonberg, P.E.,S.E. / KR7X
-------------- Original message --------------
From: "Dick Green WC1M" <wc1m at msn.com>
> K7LXC wrote:
> > My question is: why would you use a form? Most tower base holes come in
> many shapes and sizes - one with perfectly formed sides is the exception.
> Even if the sides of the hole have sloughed, just fill the hole with
> concrete - no muss, no fuss with forms and you're conforming to the
> manufacturer's specs. Sounds pretty straightforward to me.
> Well, I don't want to use a form. I brought it up because the electrical
> inspector is requiring inspection prior to backfill. That implies a form. I
> want to make sure the town understands that I'll be pouring against
> undisturbed soil and won't require a form.
> > > Would a form for a padless pier be a bad violation
> of Rohn's specs?
> > I'm not sure what you mean. Please explain.
> The Rohn specs state that the pour must be done against undisturbed soil
> *unless* it's a pad pier. In that case, you can (have to) use a form for the
> pier portion (only -- the pad is poured against undisturbed soil.) Since
> it's certainly possible to backfill and tamp (not that I want to), I was
> asking just how bad it would be to use a form on a pier that does not have a
> pad. Sort of an academic question.
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