Cladding Fixings and internal pressure

[Bartek Sz]

Is external cladding subjected to internal pressure, if internally building is fully lined, with plasterboard? I'm currently specifying fixings for vertical cladding on horizontal siderails and I'm getting requirement for 4-5 fixings from my calculations, while I can only fit max. 3. I could increase the siderail gauge, but tender drawings had smaller ones and contractor is a bit jumpy when I'm trying to change something. Any thoughts on that? Thanks.

 

[DaveAtkins]

No, I do not believe an external cladding panel will see internal pressure if there is an internal wall system designed for the internal pressure.

DaveAtkins

 

[Huevo]

No, I do not believe an external cladding panel will see internal pressure if there is an internal wall system designed for the internal pressure.

I disagree. There is some commentary in ASCE 7 that talks about pressure across different layers of cladding. It is admittedly in the context of permeable cladding but I believe it is still relevant. In addition to the strength of the internal wallboard, adequate stiffness would be required to isolate the external cladding from the internal pressure. There would need to be special attention paid to air space between the internal and external layers as well.