Following is a checklist of problem warning signs you can look for during indoor roof inspections.
1. Sagging decking between rafters. If the decking is sagging or deteriorating, the decking will also require replacement when a new roof is installed
2. Outside light that can be seen through the roof. This may be common (and not a problem) on shake roofs, since the wooden shakes will swell during wet months, effectively preventing any leaks.
3. Signs of leaking in the attic (dark spots in the wood, especially around vents, chimneys, and other holes to the roof).
4. Test dark spots in the wood to decide if they are old or current problems. If the spot is still wet, or it is soft (test with a screwdriver), the spot is a current problem. If the spot is dry and hard, it is most likely an old problem that has been fixed.
5. Signs of water damage or leaking (usually in the form of water stains or sagging ceilings), this could be due to an active leak or to condensation caused by poor roof ventilation