Too much moisture in a home can lead to mold, mildew, and other biological growth. The presence of these molds can lead to a variety of health problems including allergies, asthma and more serious respiratory problems. In addition to health problems, excess moisture can lead to problems such as rot, structural damage, and paint failure and create a hospitable environment for pests and mold. Correcting and preventing moisture problems is a first defense against termites, mold, and structural failure.
Every couple of months you should make a point of walking through you home looking up for water stains in the ceilings. Often this simple act can identify a problem before you have significant water damage. Water stains can be caused by roof leaks, or condensing moisture. There's a lot of moisture generated inside homes. Bathrooms without exhaust fans or fans not vented to the exterior, leaking dryer vents, damp basements, kitchens and crawlspaces and basements can be the source of moisture in the in the home or attic. Improper roof ventilation or uneven insulation can create "cold spots" where moisture condenses to the point of dripping onto the ceiling or wet areas on the underside of the roof sheathing. Air conditioning equipment or heat exchangers in the attic, can result in condensate dripping out of the system or off of the refrigerant lines or ducts.
Twice a year I like to check my attic for mold and leaks. Mold in the attic is generally caused by increased humidity and moisture, generally from improperly installed or inadequate attic vents, soffit vents, blocked soffit vents or a roof leak, or any other source of moisture. When I added insulation to my attic I made a point of checking the attic every six months for the first couple of year to make sure that the increased insulation did not impact the effectiveness of the attic ventilation against mold growth.
If excessive moisture builds up in an attic, over time the moisture will attract mold spores which germinate and form mold in the attic which can be seen as blackened areas in cellulose insulation, along rafters or across the roof sheeting. Black mold in your attic may be a variety of things. In most cases black mold on your roof rafters is not likely to contain Stachybotrys the toxic mold we have heard so much about. Wet cellulose (such as attic insulation) is reported to have a higher probability of being infested with Stachybotrys.
An interior drip that occurs when it rains is easy to identify as a roof leak. If you remember that water moves down the roof and look along the horizontal plane to identify the water flow. The easy way is to search the attic during a rain storm when the drip is occurring. A two day heavy rain storm in the fall or spring is the perfect time to locate the leak. Take a picture with your phone or digital camera or the leak and the general area so that the roofer can locate it on a dry day. A stain in the ceiling can be an indication of moisture buildup, dripping from an air conditioner or other difficult to identify problem. Photograph the stain after rain storms to see if it is growing. Otherwise, the source of the moisture will have to be identified.
Many roof leaks can be quickly and simply fixed by a roofing professional (certainly not me, I do not climb on roofs). Many of the most common include flashings, those architectural features designed to join roofing to the other parts of your home. Of course they may also be located within skylights, chimneys or ice dams. Identifying the location of the water infiltration will help a good roofer identify the source of the leaks.
Most roofs are not really water tight, they are pitched and designed to shed water. A newer roof is likely to leak in the valley where two roof planes intersect, at improperly flashed locations around chimneys, plumbing vents, furnace vent flashing, wall step flashing. An improperly installed roof may have left the old flashing in place and have used roof cement, that gooey black tar instead of properly reinstalling or replacing flashings they simply layer on the roof cement which is at best a temporary solution, because it breaks down when exposed to UV light. As your roof ages the roofing material- shingles, slate, shakes, whatever- may become damaged in areas, and need to be replaced. Cracked, damaged or missing shingles, slate, tiles or shakes can be replaced without replacing the entire roof. Possibly a nail has backed itself out of the roof sheathing allowing water entrance. Repairing small roof leaks can prevent larger problems. Pay attention to your home.