[TowerTalk] Rohn House Bracket and Stucco Siding

David Gilbert xdavid at cis-broadband.com
Sat Jul 5 10:55:47 EDT 2008

I agree ... as a minimum I would use a 2x8 backer board long enough to 
properly distribute the load, and then attach the bracket to the backer 
board.  Even so, the extra stress on your wall due to wind forces on the 
tower could generate stucco cracks.  I'm pretty sure no housing 
contractor would warranty the stucco over a wall that hadn't been 
structurally reinforced if a tower were attached to it.

Most lath-and-stucco installations I'm aware of use OSB (oriented strand 
board ... kind of a plywood made from wood flakes) over the wall studs, 
then a membrane (Tyvek or asphalt paper) to shed water, then a layer of 
sheet styrofoam, and then the lath stapled over that.  If you bolt the 
tower bracket directly to that sandwich you will compress and crack the 
stucco for sure.  I've seen it several times, not with tower brackets, 
but for other add-ons .... such as satellite TV dishes and even small 
4th of July flagpoles.

Under no circumstances would I cut and remove the stucco.  It will make 
a mess of your house and if you cut through the membrane by accident 
you'll get water seepage to the OSB underneath that can rot it in a very 
short time.  The hole will also be pretty difficult to patch when you or 
the next owner decides to remove the bracket.  Contrary to the 
impressions of many people, normal cement stucco itself is not 
considered a water resistant surface unless painted with a thick, 
flexible paint like some of the elastomerics.  Bolt holes in the 
membrane are usually not a problem, especially as long the bolts are 
there, but cutting out a larger section of it is asking for trouble.

By the way, for a while (maybe still) some stucco'd houses were built 
with ONLY a layer of styrofoam attached to the wall studs (with a 
membrane underneath, of course), and then the stucco lath was put over 
that (stapled only to the studs).  It made an inexpensive way to put an 
exterior finish on a house, but was structurally it was very unsound.  
Not only could such walls easily crack or puncture, without the OSB they 
had much less resistance to "racking" -- the situation that occurs when 
the wind tries to make a parallelogram out of a rectangular wall.  Some 
of the pictures I saw of storm damage to homes in Oklahoma, Kansas and 
other parts of the midwest from the really bad tornado season they had 
just a few years ago had been built that way.

Lastly, don't just attach the backer board and then paint over it.  The 
stucco underneath the board can retain moisture for long periods and 
make it rot.  If I were doing this, I'd paint the board first with a 
couple of coats of breathable paint (exterior grade latex) and put a 
layer of plastic or Tyvek (tar paper will mess up your stucco) between 
the board and the stucco.  I personally would not use pressure-treated 
wood for the backer board ... the pressure treating only protects it 
from rot and insect damage, not from weathering by sun and rain, and the 
chemicals (mostly copper or boron these days) in the wood can leach in 
the rain and make drip stains on the the side of your house below the 

Just some thoughts ...

Dave   AB7E

Jim Lux wrote:
> Looking at how they attach wooden lattice patio covers around here (Thousand Oaks, in Southern California), the typical scheme (as shown on the drawing from the building department) is a 2x8 lag bolted through the stucco into the studs or horizontal beams behind it. (The patio cover is often at the height of the lintel beam across the top of doors/windows).  The patio covers have to be able to take live loads of people escaping through second story windows above the cover.
> As you say, you put flashing or silicone sealer above the beam to keep water from going behind the ledger board.  You could remove the stucco first, but almost everyone just puts the assembly flat on the stucco surface. 
> -----Original Message-----
>> From: Jeff Stevens <jeff at mossycup.com>
>> Sent: Jul 4, 2008 8:46 PM
>> To: towertalk at contesting.com
>> Subject: [TowerTalk] Rohn House Bracket and Stucco Siding
>> 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 cement
>> 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 siding
>> -- however the diagram shows horizontal overlapping siding -- not
>> stucco.  Do I bolt right through the stucco?  Do I put a backer between
>> the bracket and the stucco?  Do I remove the stucco and put in a
>> properly flashed ledger board to bolt through?
>> -Jeff
>> KE7FRJ 
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