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[Towertalk] Roof mount tower questions...

To: <towertalk@contesting.com>
Subject: [Towertalk] Roof mount tower questions...
From: K7LXC@aol.com (K7LXC@aol.com)
Date: Wed, 16 Oct 2002 11:50:49 EDT
In a message dated 10/15/02 8:10:11 PM Pacific Daylight Time, 
jhisson1@columbus.rr.com writes:

> First, sorry for so many dumb questions/emails to the list... I just want to
>  make sure I get this right... 

    No problemo, Senor - we all started out not knowing anything. 

>  Second... this one is on topic :)
>  
>  As I have mentioned before, I think I will be settling on a roof mounted
>  tower.  Easy to install (I can do it myself or with help) and I don't have
>  to mess with concrete and digging big holes.  Plus the cost of getting one
>  delivered!  I will be mounting it on either my garage (14.9') or my house
>  (19.4').  My question is, how much stress would a roof top tower put on the
>  house?  The models I am considering is 26' or 17.5'.  I would of course be
>  following all instructions on installation (and maybe putting more supports
>  in the attic than the instructions require).  Is this pushing it for a
>  typical roof?
>  
    Not in my experience. Your building code already has some sort of roof 
load built in to their specs; i.e. snow load, windspeed, etc. 

    Using additional guy wires has already been mentioned. It's a good idea 
as it's a belt-and-suspenders approach. Just don't tension them much. I use 
generous-sized lag eye-bolts right into the roof joists.

    I do not use lag screws for roof tower mounting - they're just not meaty 
enough for me. I use the backing-plate method with all-thread previously 
mentioned. Use 2x6's or something similar, just make sure they run under 4 or 
so of the joists to spread the forces. 

    Tony, K1KP, wrote an article for QST some years ago on engineering and 
installing a 25G housebracket. It does a good job of explaining the forces 
involved in using your house for a tower anchor. He did the calcs and his 
design is fairly elaborate but  shows what's involved. 

Cheers,
Steve     K7LXC
TOWER TECH --
Professional tower services for commercial and amateur

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