Roof Leak or Condensation? What You Should Know!


During winter months, many drywall stains called in as building leaks turn out to be caused by condensation. Because these stains can be large in size, residents are often unconvinced that condensation is the cause. Also, many longer-term residents logically question condensation as a stain cause when it hasn’t occurred in their unit before. There are many explanations for these situations.

Almost all interior air has at least some moisture in it which is considered humidity regardless of amount. Condensation forms when such air comes in contact with a significantly colder surface. Water that exists in vapor form changes into liquid when it is cooled to the proper temperature. The temperature at which this occurs varies depending on how much moisture is in the air, air temperature and the temperature of the cold object. The number of variables combined with different living conditions is why condensation forms some years and not others in seemingly identical situations. A simple example is the fog that forms when a person breathes directly onto a glass surface. A larger area of fog will appear when the window is cold in winter. This deceptively simple concept creates a surprising number of condensation situations inside a home.

At cold spots, condensation forms on ceilings, walls, windows and doors. On colder days this can occur even when relative indoor humidity is below 20%. The colder the spot and the more humidity in the air, the more condensation forms. Keeping blankets against a closet wall blocks heat and can create a cold spot which forms enough condensation to grow mold. Placing a chest of drawers in a corner on two outside walls sometimes blocks enough heat that significant condensation forms. Some residents have noted that keeping window blinds open or closed makes a difference between whether or not they get moisture on windows.

Determining whether or not an interior stain is caused by condensation involves two major steps. We must first prove that the stain does not come from an exterior source and then prove that the proper conditions exist for significant condensation to form at the location of the stain. Given the proper access, both steps can usually be accomplished with a nearly perfect degree of confidence. Sometimes this takes more than a single trip.

Stains are treated as building leaks until that possibility is eliminated. In all seasons, it is best practice to see the stain from the inside before going onto the roof or viewing from outside. In colder months, after viewing the stain from inside, a humidity reading is taken and we ask the resident whether or not they run any type of humidifier. We also take note of the stain shape, age, location, recurrence and whether or not there is moisture on the windows. We also ask whether the stain dripped water and whether it occurred during rain or a large ice/snow melt. Stains that appear without rain or melt are usually condensation if conditions are right. Then we attempt to examine proximal exterior areas (roof, siding, bricks, windows, trim) for defects that could lead to the stain. If no external defect is found, or there is too much snow or ice to access the roof, we look in the attic. Almost all building leaks leave trails that can be traced to their point of origin. When we have access to the proper areas, but cannot trace the moisture path, the stain is not usually from an exterior leak. Having gathered all of the information, we usually know whether the stain is from a building defect or condensation.

Here are some common condensation causes of ceiling and wall stains:

  • A disconnected bathroom fan or dryer tube pumps warm moist air into the attic that instantly condenses on cold attic surfaces. Resulting water can pool on the attic drywall and make a stain.
  • Condensation forms on the inside of exhaust fan tubes and runs back down to the fan and makes a stain on the surrounding drywall. This is not indicative of a defect. Each time the shower is run, condensation forms on the inside of the exhaust tubes and usually it evaporates before causing a problem. However, at times, there is enough moisture that the stain forms. Again this is not a defect, but is preventable by carefully creating a place for excess water to pool in the tube until it evaporates.
  • Interior humidity levels that are not compatible with outside temperature –this creates stains at cold spots as explained. These situations are the hardest to explain. These stains don’t look like leak stains because condensation stains are usually spread out and fainter than roof leaks. They often occur as dark spots ringing the ceilings near exterior walls. They also occur on the walls, usually with higher ceilings.
  • Humidifier settings: Residents have expressed frustration and disbelief that they cannot keep their units at 40% or even 35% humidity in all outside temperatures without causing condensation. Humidifier manuals, Google searches or other sources don’t usually account for a broad range of exterior temperatures, building design and living conditions – such as residents keeping their heat higher than average, taking more showers than average or even cooking or boiling food frequently. Often times we find that over-occupied units have these conditions as well. Simply put, when residents have reduced their humidifier settings there has been a marked reduction or elimination of their stains after repainting. Please follow the chart below for the ideal interior humidity.

    If you have any further questions, please contact Columbia Roofing at 410.379.6100.

Roof Condensation—This Sneaky Problem Could Cost You


When you notice moisture on roofing, or any part the roofing assembly, your first thought may be to look for leaks. However, condensation is another potential problem that should not be ignored.


What is Condensation and How Does it Occur?

Condensation occurs when warm air is pushed up through a building and meets the colder roof structure and outside air. Rapid cooling allows moisture to form, which can be trapped in the surrounding materials. During cold winter months, the water can freeze. A layer of ice forms on the inner roof membrane, which will melt when the weather warms up.

Roof assemblies, where foil insulation covers batting insulation that is wrapped around supporting beams, are especially vulnerable. Moisture can get trapped in between the foil and the plywood roof. Buildings that are located near water or in humid climates are also more susceptible because the trapped can air hold more moisture. Lumber that was not allowed to dry properly before insulation was installed can be a contributing factor.


What Signs Indicate That Condensation Is Occurring?

These are some indicators that condensation may be the cause of your moisture problems:

• Leaks only occur in warm weather, and there is no leaking when it rains.

• Dripping is visible at midday when the sun is shining.

• Insulation below the roof membrane is wet or warped.

• Walking on the roof in freezing weather produces the sound of ice cracking. This means that ice has formed under the roof membrane.

• Water is visible near solid mechanical units that present no possibility of leakage.


What Steps Should You Take?

Condensation can be a tricky problem to identify. A professional roofing company can help you reach an accurate diagnosis. A roof cut or thermographic imaging may be necessary to pinpoint the source of the water. Depending on the degree of moisture damage, remediation could be a simple fix, or addressing the problem could involve replacement of the entire roof system.

To avoid a costly repair, building managers should schedule regular roof inspections and maintenance from an expert provider. Call on Columbia Roofing, at 410.379.6100 to ensure that your roof stays dry and in great shape for years to come.

Our Foundation


Here at Columbia Roofing, we take pride in our work. It takes a lot of trust and honesty when asking someone to help improve your home, and yet that's exactly what families have been doing for nearly 40 years with Columbia Roofing Incorporated. The path they know we have chosen is that of experience, dedication, and quality for those that call upon us. We are certified in every aspect of roofing, siding, gutters, windows, doors, and skylights, so there is no question of the professionalism we uphold. This professionalism is that of not only residential homes, but also commercial property and property management. So what does this have to do with you? Let us answer that: everything. Take a moment to think about that. Our business and our reputation would have not gone very far without you, our loyal customers. Our hard work, dedication, professionalism, and honesty result from you trusting and calling on us when you have problems with your home. So the next time your roofing needs maintenance, your siding needs some replacing, or your windows need new panes, let us earn your trust, and prove to you why families and commercial businesses have trusted us for the past 40 years.

Warm Outdoor Lighting for Boosted Curb Appeal


You may have overlooked it, but an integral part of designing your home’s exterior is lighting. It’s a design element that so many of us forget, but one that can truly set the mood of your space and help to navigate around it, too.

We decided to shed some light on a few exteriors that are inspiringly illuminated and highlight the home’s superior siding in the process. Consider the story you want your exterior to tell. Whether it’s glowing, beaming or luminous—let there be light.



At dusk, the glow of this cozy Craftsman-style home clad in HardiePlank® lap siding in Mountain Sage welcomes you in, through the gates, up the stairs and into the warm well-lit space.

Set the mood. Light fixtures can help to set the mood in your outdoor space. Whether you opt for welcoming Italian string lights on your patio, or formal sconces framing your front door, think about the feeling you’re trying to create in your home’s outdoor space. You can inject personality into your exterior by honing in on your own style. Shopping for a one-of-a-kind vintage pendant light or finding a farmhouse wall light painted in a bold color for a pop against your siding, are great ways to add flair to your home without stealing focus.



Amp up your ambiance with an outdoor fireplace. This one is surrounded by fire-resistant HardiePlank lap siding in rich Timber Bark.

Warm up your space. There’s nothing more welcoming than the warmth of a fire, people just seem to flock around it. Whether it’s a built-in fireplace, installed right into your home’s exterior wall (surrounded by James Hardie® fire-resistant siding) or a fire pit in the yard, natural fire elements can create immediate and irresistible ambiance.

Let your siding shine as you show off your style with lighting that make you want to spend more time soaking up the outdoors in a space that’s completely you.

Side Your Home in Sail Cloth!


When you think of the East Coast shoreline, sailboat silhouettes lining the coast may come to mind and you can almost hear the flap of their well-worn sails in the breeze. The classic sail shade is tough to replicate, but James Hardie found a way with its ColorPlus® Technology hue, Sail Cloth.

We love this creamy siding and trim color that seems to resemble vintage canvas. The softer shade of worn-in white adds a clean and relaxed feeling to a home’s exterior.  James Hardie's ColorPlus Technology is specifically engineered to help resist damaging UV rays, so your color will stay vibrant longer with less maintenance.

The nautical neutral looks at home with any hue in the ColorPlus Technology palette, but we love Sail Cloth paired with earthy greens like Heathered Moss and Mountain Sage, rich browns like Timber Bark or crisp Arctic White.

Here are a few homes clad in the creamy siding and trim shade alone or paired with other hues in the ColorPlus palette:




This home is clad in HardiePlank® lap siding in Sail Cloth with Arctic White HardieTrim® boards. Even though the siding is fresh and new, the Sail Cloth shade has a vintage look that makes it feel aged.





HardiePanel® vertical siding in Sail Cloth, paired with HardiePlank lap siding in Heathered Moss. The bright pop of the bold shutter adds interest and a modern sensibility.





The gables of this quaint bungalow are clad in staggered edge HardieShingle® siding in Sail Cloth. When paired with a darker HardiePlank lap siding hue, the Sail Cloth looks more subtle and light.

 Evoke the East Coast—set sail for homes clad in James Hardie siding in Sail Cloth.