 So start inside by checking the ceilings on upper floors for any stains or other signs of leaks. You also want to pay special attention to the leaks above bathrooms and kitchens. And here's why. The plumbing vents pass through the roof above these rooms, and they often break down, causing leaks. There's a rubber gasket around a plumbing vent, and that will break down. So when it happens, you should replace the gasket. And also, check for leaks above fireplaces, another spot where loose flashing can allow rain to seep in.