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Re: [TowerTalk] UST HDX589 crank-up tower base on rock?

To: <>, <>
Subject: Re: [TowerTalk] UST HDX589 crank-up tower base on rock?
From: "K8RI on Tower talk" <>
Date: Thu, 16 Feb 2006 15:19:23 -0500
List-post: <>

> That's exactly the point. I don't want to blast a hole in the rock and 
> then
> fill it up with concrete. I want to anchor the tower base to the rock with
> only enough concrete to come a few inches above grade. My concerns are the
> following:
> -How much up force will the anchors handle? There will be a lot of 
> leverage
> produced by the wind on the tower.
> -How deep into the rock should I go? A few inches doesn't seem to be 
> enough
> given the winds and exposed location on top of the hill.

Time to get a good engineer and have them look at it.  Much depends on the 
kind of rock and the integrity of the rock.  If it's granit with no cracks 
that's great, but shale can be fragile.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
> -The "T" base of the tower is drilled for three pairs of one inch bolts. 
> Can
> the holes in the rock be aligned accurately enough for the bolts to slide
> through the base holes easily? If a pair of holes are drilled a few inches
> apart will  the rock between them still retain its strength?
> -Normally, in concrete, J bolts are used and tied to the rebar in the
> footing. I guess I would need longer threaded rods with whatever is used 
> to
> anchor them to the rock on the bottom end.
> Les
>  -----Original Message-----
>  From: []
>  Sent: Thursday, February 16, 2006 10:16 AM
>  To:;
>  Subject: Re: [TowerTalk] UST HDX589 crank-up tower base on rock?
>  In a message dated 2/13/2006 3:17:48 A.M. Pacific Standard Time,
> writes:
>    >  Hi TTians,
>    >  In a few months I will be starting construction on a new house which
> will be
>    located on top of a hill on a adjacent piece of property. My HDX589 is
>    currently installed on the manufacturer's recommended base of 5x5x8.5
> feet
>    of concrete with rebar.
>    >  Test holes in the vicinity of the new house have revealed between 16
> and 40
>    inches of soil on top of the rock the hill is made of. A blasting
> contractor
>    has told me that the stone is very strong and stable and he will not
> have
>    any problems blasting for the house basement and foundation.
>    >  I won't be able to dig another hole and use the same method as the
> current
>    location. Instead, I have been told there are bolts or rods that can be
> set
>    into holes drilled into the stone and epoxied in place which can 
> support
> the
>    tower.
>    >  I will probably need an engineer but don't know where to begin to
> find one
>    familiar with this type of work or what alternatives exist. Anyone
> familiar
>    with this technique or alternative method who can steer me in the right
>    direction? Any particulars I need to provide to him/her that I need to
>    research in advance?
>        Well, getting an engineer's blessing is always a good idea. Maybe
> you can talk to a couple and get some off-the-record feedback on what 
> you've
> got and what's possible.
>        I would be in favor of using the rock as the base and then you only
> have to use a little concrete to get the top of the base a little above
> grade. Why would you dynamite out a bunch of rock and then fill in the 
> hole
> with concrete when the rock by itself would accomplish the same thing?
>        You can rent a rock corer to drill the appropriate holes for the
> factory anchor bolts - or have someone come out and do it - and then you 
> can
> epoxy them in or use rock expansion bolts - or both. It'll be real strong.
>  Cheers,
>  Steve    K7LXC
>  Professional tower services for amateurs
>  Cell: 206-890-4188
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