It just began to show up. It looks like nicotine stains on the ceiling. But no one in the house smokes. Hope it’s not some kind of Twilight Zone creature leaving its trail across the kitchen ceiling. What if its fungus growing out of control and the Health Department quarantines my house? Well let’s not get carried away.
When you have a leak in your roof, water finds its path of least resistance to travel as gravity pulls it down. It is possible that rain water could enter at the very top of your roof caused by a missing shingle on the ridge, run along the bottom side of the decking reaching a rafter and then traveling along the rafter until it drops down onto the insulation and onto the top side of the drywall. The water can then find the drywall seam and run along the entire distance of the ceiling. After a few days of drying it begins to yellow leaving that notorious stain. Mystery solved.
Seriously, when you find stains on your ceilings that means you have a water leak and it should be addressed. Those leaks will get worse over a long period of time leading to bacteria, mold, and even dry rot. Tracking down the leak may be the tricky part of repairing the problem. Leaks can often be found due to rusted out flashing, missing or damaged shingles, around pipe vents, and ventilation outlets. Finding where the leak is coming from can often be a like searching for a needle in a haystack. It may take enlisting help to find it. One person can go into the attic space and watch for water to appear while the other carries a water hose onto the roof and lets it run down until the leak is found.
Checkout anything that protrudes through the roof. Pipe vent boots (3n1’s ) are notorious for leaking. Over time the rubber seal around the pipe dries out and cracks allowing water leaks. A short term fix is to use roofing cement applied around the cracking boot, but the vent boot should be replaced as soon as possible. Flashing often buckles or rusts allowing water to enter. Dormers can be problematic as well when it comes to leaking. You may have to dig out old caulking and re-caulk. They also have flashing running up the wall and out on the roof decking. Check carefully for any problems with dry rot on the framing and siding.
Occasionally a leak might show up on the interior ceiling and thought to be coming from the roof when actually is coming from an upstairs window that has lost its seal. Or even from a crack in the joint of the second floor masonry.
Leaks can sometimes be elusive, and difficult to unmask their origin. But with determination to eliminate that ugly yellow stain… it will be worth the effort.