[GSBN] Plaster detail at Bale/Plywood Interface

Derek Stearns Roff derek at unm.edu
Tue Nov 18 08:03:55 CST 2014


Frequently, an owner will have a certain “look” in mind, without an understanding of the practical/technical consequences of trying to achieve that look.  Few people outside the world of building understand the importance of an air barrier [is it intended to be internal or external on this building?], and the water resistive barrier; nor the risks to energy performance and building longevity that will result from a “small” crack that would possibly encircle the entire house, if the owner’s plan were implemented without modification.

Ian faces two challenges:  to explain the technical problems with the owner’s desired plan, and to help come up with an alternative “look” that is pleasing to the owner, while solving the technical problems.   My guess is that the owner might not like continuous plaster detail as much as he/she imagines.  I think it looks better on paper than real life.  Perhaps some buildings nearby will serve as examples, some showing the original plan with the inevitable crack, and others that might have a more interesting, and technically reliable alternative detail.

Derek


On 18/11/2014, at 11:38 AM, Bruce EBNet <bruce at ecobuildnetwork.org<mailto:bruce at ecobuildnetwork.org>> wrote:


There WILL be a crack at that joint.  Flash & detail for it, don’t be in denial.  Articulate when you cannot hide.

Thanks,

Bruce “Been hiding out too long” King





On Nov 17, 2014, at 2:26 PM, Ian Smith <ian at lopezsmolensengineers.com<mailto:ian at lopezsmolensengineers.com>> wrote:

Hi everyone,

I'm currently helping with the design of a one-story SB house with a rectangular footprint and a simple shed roof.  The SB walls will be constructed with a wood bond beam that's in the horizontal plane around the whole perimeter of the house, supported on wood posts.  Prefabricated wood trusses will then bear on top of these beams.  The trusses will have a "right triangle" shape to create the shed roof and a flat ceiling on the interior.

On the higher side walls of the trusses, the owner would like to have plaster continue all the way up to the underside of the roof (actually, to the underside of the roof sheathing), with minimal trim/flashing, etc. at the interface/transition between the straw bales and the plywood.

I've already mentioned to him that there's the possibility that that plaster will crack at this interface (due to the differences in substrate material, plaster thickness, etc), and I've suggested that there be a control joint in the plaster, or a piece of trim with flashing or something.

I'm just wondering how the rest of you prefer to deal with this detail...

Thanks very much,

Ian Smith, P.E.
Boulder, CO, USA
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Derek Roff
derek at unm.edu<mailto:derek at unm.edu>


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