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 ...
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 <email@example.com>
>> Sent: Jul 4, 2008 8:46 PM
>> To: firstname.lastname@example.org
>> 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?
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