[TowerTalk] How do bldg inspectors handle screw in earth anchors?

Richard (Rick) Karlquist richard at karlquist.com
Thu Jul 10 20:37:55 EDT 2014


The screw in anchors, if used, would be for guying.
I guess you are saying that I must make the base big
enough to handle lateral force and I can't use the
guy anchors to hold the base in place.  Got that.
So I have a choice of having my engineer watch
and certify and/or inviting the inspector watch
himself.

Is the pressure you are talking about the amount of
force to push the anchor in (an axial force) or the
amount of torque to turn the anchor in?  With the
hand installed ones, only torque is needed.  The
screw pulls itself into the ground.

Rick N6RK

On 7/10/2014 3:24 PM, Brian Amos wrote:
> As for the utilities usually the municipality doesn't inspect their
> installations as they are self regulating.  The "screw anchors" ie
> "helical piers" are installed to a certain torque which the software
> tells the installation contractor he must meet.  As a soil engineer I
> have many times had to "inspect" the installation where I watch the
> pressure gauge and make sure they make it to the required pressure
> (which they tell me) for each pier and then I have to send a document
> to the owner stating that it complies with the design and put my stamp
> on it.  I'm not a big fan of that setup as I don't do the engineering
> but I have to certify that it will hold up.  It drives me nuts
> actually.  For a residential purpose I would guess that you just tell
> the building official when you will be installing it and they can come
> and watch. That is the only way to really inspect them.
>
> BTW: Is this for supporting the tower? Or is it for the guys?  If it's
> for the tower I suspect you will need at least one per leg and it must
> be a large tower to keep them at least 3 screw diameters apart to
> prevent interaction.  This type of support provides virtually no
> lateral resistance (especially the square chance bars that have no
> soil contact anywhere but the helix, they are all tension and
> compression, so for guy supports they work great, but not so well for
> a foundation.  I suspect that the building official won't care about
> inspecting screws for a guying system.  They usually only care about
> the foundation itself.
>
> Brian
> KF7OVD
>
> On Thu, Jul 10, 2014 at 2:21 PM, Jim Lux <jimlux at earthlink.net> wrote:
>> On 7/10/14, 10:29 AM, Richard (Rick) Karlquist wrote:
>>>
>>> Has anyone had experience getting a building permit
>>> for a tower with screw in earth anchors?  How does
>>> it get "inspected".  There is no empty hole for
>>> the inspector to look at.  Do you show him the anchor
>>> before insertion?  If you have an authorized AB
>>> Chance installing contractor put in the anchor,
>>> do they issue a certificate that you can show the
>>> inspector?  In a sense, this contractor is also
>>> the engineer and building inspector all in one.
>>>
>>
>> could it be more like a material and process inspection?
>> You have the paperwork showing you have the anchor and the mfr's paperwork
>> showing what its properties are.
>> Then you have paperwork showing you did the installation appropriately (e.g.
>> if you used a truck mounted drive, it gives a reading of the torque as it
>> drove it)
>>
>>
>> The only time I've had an "official" inspection of a structure using screw
>> in anchors it was for a temporary installation, and the guy came out, looked
>> at the plans, looked at the erected contraption, verified that what we had
>> built matched the plans, and said "go for it".
>>
>> Granted it was in an area and application where failure would hurt nobody
>> but ourselves.
>>
>> What do utilities do when installing poles with these anchors?  I find it
>> hard to believe that the city sends out an inspector to watch them plant
>> every pole and its guys.
>>
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