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Home Care Library


The Home Wizard app calculates your ideal home care program to avoid problems with your Attic, but sometimes trouble can still occur. Here are answers to questions about attic moisture leak in ceiling.


We have a room with a vaulted ceiling. Dark lines are starting to appear on the flat portion of the ceiling, next to the vaulted portion. The lines follow or outline the roof trusses. What can be causing this? If we paint over them, how do we know they will not come back?


Dear Cindy:

It sounds like you have moisture leaking into your ceiling, and it is traveling along the ceiling joists, getting this area wet and likely attracting mold.

Because of the construction of vaulted ceilings, there are often number places where the roof lines intersect. And the places where the roof lines intersect they are covered with pieces of thin metal called "flashing". Over time (or if it was not installed properly), this flashing loosens up, and can allow water to come in through where the two sections of roofing meet. This could be where rain water is dripping into your ceiling, and then running down until it hits the ceiling joists.

The other possibility is that if there is not proper ventilation in your vaulted ceiling, and that when the warm moist air in your room meets the cold wood of your roof, that it causes moisture to condense out into your ceiling.

And yet another possibility is that, depending on the orientation of your roof lines (and the region of the country that you are in), that the moisture could be due to "ice damming", which is causing water to puddle on your roof, and then to seep into your ceiling under the shingles.

But to answer your question, yes, if these lines indeed are caused by mold due to moisture, then if you just paint over the dark lines they will keep coming back until you eliminate the source of the moisture.

You might want to start by talking with either a home inspector, or a qualified roofing contractor, who can inspect your particular situation and pinpoint the specific likely source of your moisture.

Hope this is helpful.