A customer asks about venting a lead roof Spired on by my Youtube vide Lead Roof Venting Lead is beautiful & cross venting vital for a cold deck roofs. Warm deck usually avoids the need for cross venting but I notice that the LSA & other lead sheet groups recommend cross venting even a warm deck flat roof where this should be unnecessary for a warm deck roof. What is your opinion on providing yet another set of counter battens & decking on top pf a warm deck roof when lead sheeting is applied rather them single ply? Have you ever seen or experienced internal sweating of a lead sheeted warm deck roof? Is it an over precaution when using lead? What is your view from the sharp end? Surely if the visqueen FB vapour barrier is applied well under the insulation & sealed to all the abutments, cross venting the top side of a warm deck roof should be totally unnecessary. REPLY The perfect flat roof is a warm deck roof with a cold vented roof over the top. The cold vented roof allows any moister that gets past the warm roof to escape basically you are building in redundancy into the [...]
The lead on these flat roofs is beginning to oxidise and break up before the end of its lifespan. Lead on roofs and flat roofs are supposed to last 30 to 60 years with very little maintenance. What we see more and more is lack of ventilation and roofs sweating; this problem is happening because of the lack of ventilation under the lead flashings.