Expansion joints in stucco

Ask the pros- August, 2001
By Reggie Bullard


We are currently building a house in the Clarksville, MD area that will have a traditional stucco exterior. The Tyvek home wrap is up and the metal lath attached.

In the attaching of the lath, the installer has placed an expansion joint 
everywhere around the house between the first and second floors. Also, he has placed expansion joints vertically above and below every window corner (1st and 2nd floors). There are quite a few windows. 

From a look perspective, my wife and I hate all these joints. Also, our house is designed around a center courtyard which has mainly windows and glass doors surrounding it. The courtyard is not huge, and with all these vertical expansion joints, it looks like you could play tic-tac-toe on the walls. My wife asked the general contractor what the difference was between getting cracks and having cracks preinstalled. Actually, a little minor cracking would be acceptable over the look of the expansion joints.

The general contractor and the stucco sub have said that the placement of expansion joints at all corners of the windows and doors is per the  "specifications". If we wanted any of the joints taken down, they said we would have to sign something saying we requested this and that if cracks occurred, it would be our problem. Also, we would have to pay to have the joints taken out.

Is there any way of filling the expansion joints so they are not noticeable? Also, the sub is pushing an elastometric finish coat from Finestone (supposedly to help reduce cracks) on top of the traditional 3-layers. Is this OK to use with traditional 3-coat stucco? Do you recommend keeping the expansion joints? Can we take just a few out? Is there a rule of thumb on where these joints would go (if we decide to have some)? Are you available for hire to inspect/consult/help us understand and make decisions (I've already had to hire a structural engineer to consult on a problem, but that's another story...)?

The sheathing on the house is plywood. If the floors are any indication, I do not believe they spaced the sheathing at all. I'll check. 

Thanks for any advice.

Expansion joints are ugly, particularly the metal
factory made type. The rust, rot and allow water to
get behind the wall, possibly delaminating the stucco,
not to mention staining the wall.
We don't use them any more, since I don't
do much government work, unless we make
a homeowner insists and I can't talk them out of
it. In that occasion, I make a homemade joint.
We have been using a concrete groover which works

I write my own specifications, which say expansions
aren't necessary, because the didn't have them 70
years ago.

The only specification I know of is by United States Gypsum
(who makes the metal joints), that say for cement stucco you need a joint 18 feet O.C. max.

But the condition is that the lath be broken at the joint,
that is the joint put on first and the lath run to the joint
or a gap left in the lath behind the joint.
NOBODY does this. I never did, hell, it takes to long.

If the joint is nailed over the lath, which is probably the
case, it isn't installed according the manufacturer's
recommendation anyway, assuming they made the joints,
which may be unlikely anyway.  If so, you can easily rip
them off without disturbing the lath. If it is your house, I
wouldn't pay to rip them off.
Another thing is these need to be set with a string line
with the plane of the finished wall, and should be
within 1/8" true every 6 feet. If there are any humps
or dips in the joint, they will show on the
finished wall a mile away. The expansion shows
things that you can normally get by with.

Another thing I think looks ugly is synthetic finish.
There is nothing nicer than a color portland cement finish.
It looks expensive and hand done. But, each to his own.
I have put synthetic finish on at the insistence of a homeowner,
but I am sure in traps water against the wall.
I can prove it.
You will probably be hard pressed to find a manufacturer
that recommends putting synthetic finish (elastomeric) on a cement
base coat except for the one-coat "stucco" crap of styrofoam.
There are companies trying to pawn off the one coat crap as
"traditional stucco".
Hairline cracks shouldn't hurt a thing. I have never guaranteed
stucco against cracks, although in the last couple of years I have
cut the cracks down to none or very few by using plasticizers
in the mortar.
No one guarantees concrete against cracks.
Excessive cracking and big nasty cracks should be
an exception, including spider-webs(checks) and
cracks due to abnormal shrinkage.

The spacing recommendations are stamped on every
sheet of plywood.

I would go rip off those expansions with a crow bar.
If you filled them in later they would look worse.

I am only available to hire in the evening because
we have way too much work.

Hope this helps.

Thanks for visiting my site.


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