I am currently building an extension that has a vm zinc roof surrounded on three sides with a parapet wall made up of cedar cladding. I have heard conflicting reports on the effects of using these materials together. Although both materials are not in direct contact the roofing contractor seems to think that the rainwater run-off from the cedar cladding will damage the zinc roof and may eventually break down the roof. I have also spoken to a timber 'consultant' who maintains that over a relatively short time the acids will leech from the timber and be washed away without having enough time to damage the zinc. I have 'googled' this problem and cant find anyone that agrees with the 'consultant'.
If anyone has experience of using these materials together I would appreciate their advice. Thanks