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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