When using a non-breathable underlay in a cold roof, the underlay should be placed over the underlay support tray fitted above the eaves ventilation strip. When using a vapour-permeable underlay in either a warm roof or cold roof with an air impermeable roof covering, the underlay should be placed under the eaves ventilation strip in order to facilitate ventilation to the batten/counterbatten void beneath the roof covering.
Disclaimer - The information shared in this blog is correct at the time of publication. Guidance, standards, and best practices may change over time, so if you’d like further clarification or the latest updates, please get in touch with the Marley Technical Advisory Team, who will be happy to help.