Lathing Under Metal Roof

To make clear to readers if firring strips battens are used this should be located under the firring strips so the ventilation airspace is right under the metal where condensation is most likely to occur and to keep any roof boot flashing leakage running off over the top of the water barrier from contacting and corroding the underside of the roofing metal like it would if the water barrier were directly under the roofing though that is the case with roofing direct on sheathing without. As for ventilation the creation of air compartments under the metal roofing using horizontal lathes does not constitute ventilation as the air compartment need to be joined vertically to allow air movement by convection. Metal roofing panels rated for architectural use attached to purlins horizontal pieces of wood or metal fastened to roofing trusses are structurally sound when installed according to your roofing manufacturer s instructions and local building codes.