[TowerTalk] Rohn House Bracket and Stucco Siding
jimjarvis at optonline.net
Sat Jul 5 07:17:20 EDT 2008
Jeff, Ke7FRJ wrote:
> Stucco isn't particularly common in my area. What is the proper
> way to
> attach a house bracket to a building with stucco siding? This is
> stucco over metal lathing -- not EIFS.
> Of course, following the manufacturer's specifications is the way
> to go.
> Radian *does* show the bracket attached directly to the exterior
> -- however the diagram shows horizontal overlapping siding -- not
> stucco. Do I bolt right through the stucco? Do I put a backer
> the bracket and the stucco? Do I remove the stucco and put in a
> properly flashed ledger board to bolt through?
To which Dave Robbins, K1TTT replied:
Only a proper architect could tell for sure... but I would be afraid
bracket cracking the stucco. Remember, the bracket takes all the side
forces on the tower so its going to be pushing and pulling on that
the wind changes. So personally I would go with a separate ledger
be sure to bolt well into the inside structure. Remember, lag bolts
2x4 wall probably won't hack it... the note in my older rohn catalog
house bracket installation is "the interface of tower brackets to
structure is to be designed 'by others' and must support a minimum
horizontal force of 815 pounds." The way I look at that is to
attachment point with the wall laying on its side and think about 5
hanging from it, if you aren't comfortable with that its probably not
To which I will add N2EA personal experience and bias:
The rohn house bracket is intended to clear a deep overhang. It's a bit
flexible, as a result. I have always backed my house mounted towers
with a 2x8 which extends over 3 studs or roof joists. That is, it
over 48" long.
In VT, I had a situation where I couldn't use a backing board, and
had to lag
screw into the face joist, and roof truss joist ENDS. Not a
I used 1/2" x 12" lag screws, rated at 2500lbs extraction force if
pilot holes providing 100% thread. I performed a 1,000 lb
on one bolt using a come along and a tree as a deadfall.
You might want to calculate the worst case overturning moment on the
bracket, in the extraction axis, just to make sure you have a safe
reserve. That calculation, in itself, should be a thread here!
After excruciating investigative work, I managed to position 6 lag
the center of the roof joists, 2 per joist, spread over 48", with
the load distributed
across a 2x8. Carriage bolts were seated in the back of this plate,
bracket to be bolted on.
This mechanism was repeated at the floor truss system. The tower
supported at 6' and 16', and was floored by sitting on bedrock. No
foundation. It held 60' of 45G with a foldover section, with 10sf
and through two hurricane backwashes, with no problem, for 6 years.
When we sold the house, it was a simple matter of filling 12 holes
and touching up
As for the stucco texture, you may see some compression of it, but I
cut it away and flash. Leave it intact, and touch it up, if needed,
when you strike
Jim Jarvis, President, N2EA
The Morse Group, LLC
coach at themorsegroup.biz
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