Dear buyers, here’s how to spot a problem roof

Q. We noticed that plywood under one side of the roof and on one half of the attic feels wet to the touch and is turning black. The other side is dry and fine. The wet side is on the west and north, and the dry side is east and south. We have soffit vents and (supposedly) a ridge vent, and we were told to cover gable vents, as they are incompatible with a ridge vent. There are no trees around the house. We had the roof replaced 13 years ago. There are no leaks, so this appears to be a ventilation problem. We are having difficulty finding an appropriate contractor for this issue: The roof contractors don’t want to touch ventilation problems, and roof vent installers want to talk about vent installation, not fixing our problem. What specialist should we be working with to have this problem troubleshooted and fixed?

M.L., Boston

A. There are potentially two things going on here. Clearly, there is moisture making its way into the attic. A dryer or bath vent may not be connected to the outside, so it may be dumping moist air into the space, leaving it to condense on the underside of the sheathing. But the more likely source is poor insulation in the ceilings (or attic floor). That would allow warm, moist air to escape into the attic space during the heating season, then condense onto the underside of the sheathing. A humidifier would exacerbate this. The reason the south and east roof sheathing is not affected is that the sun heats up that side of the roof, drying things out.

Spring is a great time to check your roofing and address any concerns before they become major headaches. Winter can be brutal on a New England roof. The wind and snow can blow shingles loose, and dropping branches can damage roofs and gutters. Animals can do damage to roofing and flashing. Some critters will sense a heat source and try to burrow their way into the space during frigid snaps.

What homeowners and home buyers should look for:

■ Make a visual inspection from the ground. Look to see whether shingles have blown off. This typically happens up high on the roof, especially at ridge caps that run along the top of the house.

■ Look for shingles that have curled (some people call that “baconing”), which means they have outlived their life expectancy and you may need a new roof. From the ground, you may be able to see that the minerals have worn off the shingle, exposing the asphalt base — also a sign you may need a new roof.

■ The flashing used against chimneys, skylights, roof vents, and the walls that abut the roof all need to be in good repair. These are difficult or impossible to see from the ground, so a roofing professional should inspect these areas.

■ Check the gutters and downspouts. Typically, gutters are cleaned in the fall, but debris can fall into them over the winter. Depending on the types of trees on the property, you may have to have your gutters cleaned twice a year. Be sure the downspouts are running freely and that extensions pull water away from the house.

■ Some homes have very high roofs (often slate), and in the city, all or part of the roof may be covered in EPDM rubber. You should have a professional inspect these roofs. It could be dangerous trying to inspect these without the right equipment. With rubber roofs, the problems are often difficult for an untrained eye to find.

Now, turn your attention to the inside:

■ Ensure there is adequate insulation to keep warm, moist air contained inside the living area and not have it get into the cold attic and condense on the sheathing. Over time, that could lead to the most expensive type of roof job: replacing the sheathing and the shingles. Ensure that any mechanical venting is connected to the outdoors.

■ The science of attic venting is all over the place, but one thing is for sure, you want the attic to breathe and allow the built-up heat to escape. Attics can reach into the low 100s on a hot summer day. Ridge venting is very effective, and so are rooftop vents that get woven into the shingles. Rubber roofs should have something called a turbine vent that spins with the heat rising and expels the hot air faster. Depending on the roof configuration, thermostatically controlled motorized vents can be quite effective. Excessive heat buildup in the attic space under your roof will take years off its life.

Your roof is like any other part of your home; it is a system that needs to have all its various components working for it to be the most effective. Like going to the doctor or to a trusted mechanic, a combination of your own visual inspections and a professional assessment every year or two will go a long way.