Expanding on expansion joints.
A picture from a reader in Florida:
No, this isn't a stucco expansion joint.
It is a drywall expansion joint.
It can still be used. The mortar would need to
be struck off flush with the
inside edge of the joint.
A joint made for stucco
would leave a much nicer job.
The cracks on the edge are probably OK as long as the
mortar bonded fine to the block.
The cracks will fill in with the brown coat.
Drywall expansion joint with an 1/8" flange
Expansion joint for stucco with a 3/4" flange
Note how the stucco expansion has larger holes
for a good key for mortar. The mortar should
squish through nicely for a good bond to the block.
Also, the raised flange has a nice casing for
locking the mortar in place, and provides a neat,
finished edge.On framing where metal lath is
required, the joints should be put on first, overlapping
the side flange with metal lath.