Info on Stucco and Plastering-February, 2007 - twenty-fourth issue
In traditional stucco work, is there a distinction between control joints and expansion joints ?
Yes. but very little.
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
materials.
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.
If you have followed my site, you may have seen that I don't like control joints because I think they are ugly,
and completely unnecessary. Old houses didn't have control joints, and we mainly work on old houses.
I have heard that these joints are necessary. We work in old neighborhoods where the stucco houses are in
good shape, and have no control joints. However, we work on fairly new houses with control joints that
are rotting and falling apart.
A view of a double "V" expansion joint.
A true expansion joint is made in two pieces, like this expansion joint from Flannery Trim.