Plaster

[Hayley]

At what temperature does plaster crack?

[philo]

It's not so much that plaster cracks because it got too cold as it is a matter of settling and the contraction of lathe.

[Ed Pawlowski]

It is not really temperature dependent. Plaster cracks when walls move enough to stress it and that depends on overall construction. It can readily take below freezing temperatures with no harm in a well constructed building. Proper application, thickness, stud spacing, lath, are all factors.

[trader_4]

+1

Temp drop causes contraction, but I doubt there is any magic number. Like you say, it would depend on the underlying structure. Same thing with drywall. It's the shrinkage/expansion/movement of the whole structure that causes it to crack at joints.

[Frank]

Might also mention that in the winter when humidity is down wood also contracts leading to stress cracks.

[Paintedcow]

One thing I never understood was why we dont put expansion joints in plaster. We do it with concrete, like sidewalks and roads, but not with plaster. Yet, plaster is a type of "concrete" and its gonna expand and contract similarly, particularly in a home that is not heated in winter or cooled in summer.

[TomR]

That wouldn't work for plaster in the way that it works for concrete.

Plaster is tied in to the underlying wall structure -- wood or metal lath, wall studs, the ceiling structures, etc. So, the only way the "expansion joints" for plaster would work would be if the entire wall had expansion joints. That would mean gaps in the entire way as it expands and contracts.

Concrete is not tied in to the base below it it. So, the concrete can expand and contract on its own without the underlying structure needing to expand and contract with it.