Excess moisture is the reason for water streaks on interior walls. This moisture can come from a number of places. Once you know the specific reason for the water streaks on your walls, you can repair the problem and clean the unsightly stains away. Keep in mind that water streaks are more than simply an eyesore -- they could indicate rot and mold growth behind the wall, a fact that puts a sense of urgency on repairing the issue as soon as possible.
Roofs can become leaky when they are damaged. Likely causes of roof damage in cold climates are ice dams. The water behind these frozen dams builds up and often finds its way beneath the shingles. The most likely place for this to occur is directly above the exterior walls because warm air escapes here and melts the ice. When this happens, water streaks appear near the top of walls in rooms located on the highest story of your home.
Leaves, twigs and other debris collect in your gutters unless you clean them out regularly. Poor drainage allows water to seep under the shingles or create water problems at your home's foundation. If water from your roof is directed toward the foundation instead of away from it, you may notice water streaks on interior walls near the floor of the first story or coming down from the ceiling in the basement.
High Indoor Humidity
Sometimes water streaks on interior walls aren't caused by moisture on the outside at all. There are several indoor sources of moisture that lead to water stains, including domestic activities, such as cooking, showering, clothes washing and even breathing. Continuous overuse of humidifiers, clothes dryers that vent into the living space, crawlspaces without vapor barriers and plumbing leaks are all issues you can remedy to solve the problem of high indoor humidity levels.
If your home has a moisture problem resulting in water streaks on interior walls, the best way to fix the problem is to increase ventilation. Spot ventilation is the use of exhaust fans in particularly humid areas of the home, such as the kitchen and bathroom. If spot ventilation isn't enough to get rid of excess moisture, a whole-house ventilation system should be considered. Whatever kind of ventilation you select, ensure that exhaust fans are vented to the exterior, not the attic or another interior location.