Through-Wall Flashing Necessary for Rain Screen Panel system?

[Marko04]

Hi,

I am currently in a process of designing a rain screen panel system that will utilize a stand-off clip and girt to hold the panels. The panels will sit approx 3 -5"(depending on the thickness of
esterior insulation) proud of substrate.
I am wondering if through-wall flashing is necessary for such a system. The image attached is a detail in -progress that I am working on and it shows a deflection joint where two girts are separated by approx 1 " to allow for deflection
of the slabs. I am wondering if I need to incorporate thru wall flashing at this deflection joint or anywhere else along the vertical line of the wall?

I figure I would not need a through-wall flashing since the joints of the panels will deflect almost all the rain away, but, if any wind-driven rain shall find its way through
the panel joints then there are many drainage planes where this residual water can ran down from ( back side of panels, girt top planes, sides etc). In addition, the
volume of the air space would provide ample ventilation that would further dry out any residual moisture.
My only concern is would a through -wall flashing be needed if the panels are to be used on high rise building and sky scrapers of many floors where sum total of all residual water that
was able to get behind the panels at each floor would needed to be drained at every floor?
What are your thought on this?

http://files.engineering.com/getfil...b-a787-17d4df891e49&file=deflection_joint.jpg

I would greatly appreciate any feedback.




Thanks,
Marko

 

[Ron]

Yes! A through-wall flashing is absolutely necessary.

 

[Marko04]

Thanks for the quick response Ron. Appreciate it. The main reason I was wondering whether trough-wall flashing was required is after looking at on route and return panel systems like Alucabond, Trespa and contacting Alucabond representatives, they told me that route and return systems don't use through wall flashing, instead, they use weep holes at every panel.
So does this mean that if I don't integrate a through wall flashing, the weep holes would suffice?

Thanks

 

[Ron]

No. Alucobond and other similar panels will collect moisture within the cavity, with only drain holes in the alucobond panels, you cannot reasonably remove such moisture. Provide a thru-wall flashing that removes accumulated moisture without the need for drilling drainage holes in the Alucobond panels.