I needed a use for old CDs and DVDs. My friend runs a website selling media items (mediamad.co.uk) and he gave me a stack of CDs and DVDs that he couldn't sell for a project of mine that never reached completion. To use them up I thought up this, and after not being able to find it on the web or instructables, I felt obliged to follow Kiteman's zeroth law
This method of drilling, arranging and nailing disks works great for any roofing that has wooden board underneath. Structures like sheds, dog houses, lean-tos and porches are easy to cover and it makes a great hard-wearing, long lasting (I hope), cheap and most importantly.... green, method of roofing.
CDs and DVDs are readily available if you scrounge around. Ask friends, post on local sites like freecycle or craigslist, ads in the free local paper; these ways soon add up to thousands if you're happy to do a little walking/cycling around your town to pick them up.
Using this method, you need as few as 120 disks per square meter, and the method of drilling and arranging used means no water runs through the holes in the CD!