 Well, the average roof leak does take up to two years to show up inside your home as a stain. I mean, that's a long time for water damage to be happening. If you use a pro to inspect your roof once a year, that really is the best way to spot problems early. However, there are plenty of things that you can do yourself to identify signs of potential leaks. So start inside by checking the ceilings on upper floors for any stains or other signs of leaks.