[TowerTalk] Pier-pad foundation, under a house?

[Bryan Fields]

I'm not sure why threading is all messed up with this thread.  Probably
outlook messing it up.

On 8/26/14, 6:21 PM, Kenneth Goodwin wrote:
> The AN Wireless Tower foundation as I view is a specialized pad since all
> three legs are attached to a contiguous piece of concrete.  I calculate that
> it would be at least 10 cu yards of concrete for a foundation F at the
> desired wind load.  The type K foundation is probably 18 cu yards from the
> slightly inadequate dimensions given in the original post. 

The K foundation is about 19 yards for the Pier and Pad.

I've put a site plan and some of the documents of the tower up here
http://keekles.org/~bryan/Tower/

You can see in my site plan where the tower pier would be and where the pad
would extend under the house.  It

I've been talking to my local PE here who doesn't have experience with small
towers such as this, but he thinks it's doable.  However both AN wireless and
him are saying I need a geotech report, and that alone will be about $3-$4k.
I'm looking for some opinions before pulling the trigger on the engineering :)

My budget is about 15k; figure about 4k for the base, 4k for engineering, 6k
for the tower, and 1k for the crane rental.   Plus lots of my own sweat.

It's just a matter of possibly going a bit deeper with the pad and supporting
the house foundation while we do it.  The house is a combination of piers and
slab (1945 construction that's been added onto...).  The piers are on the
south side of the pad, and the slab is on the east side of the pad.


> I see that AN
> Wireless provides a DIY estimator that may have resulted in what was posted.
> I would view that as a very viable estimation, whether it is accepted by the
> City or not is an unanswered question. The depth of the AN Wireless pad is
> held constant which makes for a large pad.  The same holds for Rohn's self
> supporting tower (SSV) pad foundations.  Rohn increases the both the depth
> and width of the their pier & pad designs (for each leg) as the tower height
> increases but only starting at a tower height of 140 feet since anything
> less than this results in a pad foundation.  So depending on the soil
> analysis and wind load, it would look to me as if one could decrease the pad
> width as the depth increased or as KK9A stated, use an alternate foundation
> design.  But this knocks out the AN Wireless pre-provided stamped drawings
> as I would guess is being implied in the original message.  As a PE, I would
> never stamp a design without a soil analysis anyway.  

The City is cool with it up to 70' provided I have stamped drawings.
It must be in the rear of my house and be 15' from the property line.

I'm just pondering how I can "jam" a tower in my small back yard.

My intent is to over build the foundation to support a 100' tower, and later
down the line go get a variance for the extra 30' if I decide to.  At 120 MPH
BWS, the 70' SHD supports 135 sqft (round), and with the extra 3 sections to
100' the tower still support 55 sqft  of antennas.

I'm only looking for a VHF beam and some microwave stuff right now, but I
might decide to put up a huge antenna in the future if I get into HF.  I want
to have that option.  I've also climbed an AN wireless tower before, it was
rock solid at 120', I cannot say the same about other towers marketed to hams.

> For the magnitude of
> both the AN and Rohn pad foundations, I would view the tower foundation as a
> reinforcement to the house foundation as long as nothing was under the house
> foundation.  It sure was the case for my tower's pad foundation since it was
> the only area of the house that didn't require a slab foundation repair
> after 30 years in the Texas gumbo.  Ken K5RG

Only thing under the house is sand.  :(

-- 
Bryan Fields

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