[GSBN] Lime plaster and expansion joints

[John Zhang]

Dear All 

This is my first post over a long period of time. One way to overcome
the problem as Jeff described is to have steel posts or any type of
posts embedded into the bale wall either in right in the middle or away
from the exterior face of strawbale wall. Of course cross bracing then
become tricky, but still can be achieved by careful detailing.

 
Regards

 

Dr John Zhang, MIEAust, CPEng, NPER (Civil and Structural), RPEQ (Civil)

Senior Lecturer in Construction

================================================

Head of Program, Bachelor of Construction Management

School of Engineering, University of Western Sydney, 

Locked Bag 1797 Penrith South DC, 1797, NSW, Australia

 

Voice: (02) 4736 0908      Fax: (02) 9852 4300 or (02) 4736 0833

Mobile: 0449 254 709  Email: j.zhang at uws.edu.au

==================================================

 

-----Original Message-----
From: GSBN-bounces at greenbuilder.com
[mailto:GSBN-bounces at greenbuilder.com] On Behalf Of Jeff Ruppert
Sent: Monday, February 09, 2009 4:09 AM
To: (private, with public archives) Global Straw Building Network
Subject: Re: [GSBN] Lime plaster and expansion joints

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


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