metal roof installation questions
I've been reading all the pros and cons of metal roofing and am still trying to decide if it is our best choice. We are adding a small room on to a cabin on Vancouver Island. We will then reroof the entire structure which currently has several different roof slopes. The new roof will be a straightforward 3/12 roof, about 45 feet long. We are surrounded by large trees, get lots of rain, occasionally we can get big dumps of snow. The cabin is mostly used in summer with occasional winter stays. We are looking for low maintenance, something that is less likely to grow moss, fireproof, no leaks!
We are looking specifically for info on installation but also welcome people's opinions. We have had two installation methods recommended:
1. sheath entire new roof in plywood, cover with waterproof membrane then cover with special plastic mesh to allow air flow (don't know what this is called - it looks a bit like a brillo scouring pad, about 1/2 inch thick, very sturdy)
2. nail 1x4 boards perpendicular to rafters (side by side for first two feet, then spaced, waterproof membrane overtop then metal roofing is screwed into 1x4s.