COP:penetrations; general

8.1 General 

Penetrations may be executed in roofs of any pitch down to the limit of 8° for corrugate and 3° for other profiles. Penetrations are not allowed in the portion of curved or drape roofs where the pitch falls below these limits.

Designers are urged to provide for multiple penetrations such as air-conditioning ducts, by using a separate plant room that is not only the most weathertight method but also the most economical one.

All penetrations must be made watertight using flashings.
Where more than one rib of profiled cladding is removed, additional structural members must be provided to support the roof cladding.

For large penetrations, the supporting framework should be in position before the roof cladding is fixed. Alternatively, if the position of the penetration can be adjusted to suit the profile, the supporting framework should be in position before the hole is cut in the cladding.

Small vent pipes and ducts less than 150 mm do not require additional structural members unless more than one rib is removed.