Difference between control joint and

expansion joint?

Ask the pros-February 2007
By Reggie Bullard


In traditional stucco work, is there a distinction between  control joint and  expansion joint  ?

Yes. Expansion joints were
made for two reasons-one to control cracking
due to expansion and one to provide a stopping
point for the application of materials. A control
joint provides a stopping point or a break in applying
Stucco finish coat must be applied from edge to
edge, or corner to corner without stopping.
If the mortar sets up before the wall is finished it
will leave a bad join, or a nasty line on the
wall. You can sometimes see this in old buildings
at the scaffold level when the crew wasn't big 
enough  to bring the wall down quickly.
Even joins in the brown coat can be "read"
through the finish, because the join absorbs
water differently.
Heavy dense materials like stucco, concrete
etc. expand and contract with humidity and
temperature. Lightweight materials, such as 
EIFS don't really expand at all, but the joint is used
as a stopping point. The synthetic finishes are more
unforgiving in leaving joins. The joints here are just
control joints, or a place to stop.
In the old days, before anyone thought of expansion
joints, big houses sometimes had decorative bands
to provide a place to take a break.
In EIFS or synthetic "one-coat" stucco the control joints
just give the mechanic a stopping point, even though
they are referred to as expansion joints, they are really 
control joints, or a place to stop.
I am blessed with a big enough crew to finish a 
big wall from top to bottom without stopping.

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