[TowerTalk] Re: House Bracket

[Nat Davis]

>Preparing to install US Tower MA550. Following manufacturers suggetion using
>a 18" x 18" by 18" base with a house bracket at about 19 feet. Planning to
>connect the house bracket by removing fascia and replacing with laminated
>green treated board, which I will lage screw into the ends of about 4 or 5
>roof trusses, then I will lag screw the bracket into this board...
>
>Does this seem like the right track? I don't want the tower to go over or
>wreck the house!
>Thanks Dave K0XH

Dave,

The best information that I could find last fall when building my 
house-bracketed 30' Rohn 25 tower was a detailed article in the August 
QST.  It covered the construction of a set of 2 house brackets for a 
tower.  I modeled my single bracket after one they used.  Find the 
article.  It is worth a look.  The thing they stressed is tying the bracket 
back into the house structure in a substantial way.  I would be concerned 
about lag screwing into the ends of the trusses -- end grain and screws 
might be a weak combination, as someone else commented....

Here is my description of my bracket, from my Sep 99 summary to 
towertalk.  Hope it helps:
>To support the bracket and distribute the stress loading of the bracket, I 
>nailed 4 20" wide by 6' long pieces of 3/4" plywood down to the joists at 
>the end of the house.  The size of these pieces came from the width of the 
>opening to get into the attic.  I would have preferred to have only 2 
>wider/longer pieces, but that was not to be!  The plywood spans 4 joists, 
>counting the one against the end wall of the attic.  On top of the 
>plywood, I lag-bolted a 6' long 2x8 to the studs of the exterior 
>wall.  This 2x8 spans 5 of the wall studs.  On top of the plywood and in 
>front of the 2x8, I then attached a 3.5x3.5" piece of steel angle iron 
>that is 4' long (and a 1/4" thick).  The angle iron is lag-bolted to the 
>plywood base.  I also added 2 1" wide x 4' long steel "wings" that are 
>bolted to the bottom part of the angle iron and are spread out on the 
>plywood and lag bolted down to the joists.  The 6 holes for the bracket 
>mounting bolts are centered in the length of the angle iron.  The bolts 
>for the bracket will go through the Rohn house bracket (HB25CG), the wall, 
>the 2x8, and the angle iron.  This approach seems to be real solid.


Good luck in the design!

73,


Nat Davis
N4EL


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