2x4 for purlins seems massive! Do you have a link to the install specs?
If you have rafters & osb, I'm not sure why you'd need purlins at all - just battens for attaching the cladding.
Cross-battening for channel cladding would be to allow airflow, rather than water flow. If your cladding is corrugated, though, I don't see any need.
Agree with this. Corrugation does the job of cross-battening. There shouldn't be running water under the cladding but you do need adequate ventilation to stop moisture buildup. The ridge capping/detail should allow airflow too.
@hoefla started 4 years ago
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2x4 for purlins seems massive! Do you have a link to the install specs?
If you have rafters & osb, I'm not sure why you'd need purlins at all - just battens for attaching the cladding.
Cross-battening for channel cladding would be to allow airflow, rather than water flow. If your cladding is corrugated, though, I don't see any need.