[GSBN] Lime plaster and expansion joints

[Jeff Ruppert]

Laura,

The horse arena that we built near you has had more cracking on the 
exterior walls than I expected.  We placed regular expansion joints on 
every post, which were roughly 20 feet apart.  The frame was steel. 

In looking at the cracks it seems that the expansion of the frame in a 
vertical direction places the panel in tension and creates the cracks.  
The vertical expansion joints don't do anything for this action. 

The interior plaster on the same walls do not show many cracks.  The 
frame is against the exterior face of the wall and the mesh was attached 
to the frame. 

The interior bale walls on the same project which are not exposed to the 
extremes of the weather have not cracked. 

In doing it over I would have found a way to not attach the plaster to 
the frame.  I am not sure how this could have been done easily, but 
steel frames expand and contract with temperature so much that attaching 
a rigid material like plaster to it can be problematic.  Maybe 
horizontal joints would have helped a little, but I doubt it.  From the 
appearance of things the magnitude of expansion and contraction was just 
too much for any type of plaster to deal with.  I would expect the same 
to happen with both earth and lime, unless you make them elastic or tell 
the to stretch when it gets hot. 

If your frame is wood these issues are going to be easier to deal with.

Jeff Ruppert