If your ceiling is water stained, it's a safe bet you have either a roof leak or a condensation problem. It's important to figure out what type of stain you have before you repair your ceiling.
Fortunately, these stains are easy to identify. The condensation stain is usually found on a ceiling panel near an exterior wall, often in a corner. Instead of one large stain, you'll see several smaller circles of stains. These stains vary in size and shape, but they tend to have white centers. Condensation stains appear even if there has not been a rainstorm.
The rain leak stain can be found anywhere on your ceiling: near an exterior wall, surrounding a ceiling fixture, around a ventilation pipe or even in the center of the ceiling. This stain tends to be concentric rings that get progressively lighter as they move outward. The center stain is dark, because it is the oldest stain. Each “ring” by the way, is a separate occurrence. If you see lots of rings surrounding the dark stain in the middle, you know the roof leak has been around for quite some time.
Don't bother replacing the stained ceiling panel(s) until you have stopped the roof leak. To do that, you first must locate the leak. If you're lucky, the leak will be a small roof hole right above the ceiling stain. Unfortunately, roof leaks are rarely that easy to find. It's possible the hole in the roof is not even close to the stain in the ceiling. It's also possible the hole is a tiny space between the flashing and the roof.
To find the roof leak, you must check the entire roof very carefully. Remember to walk on the rafters or a sheet of plywood so you don't damage the seams. Be sure to inspect:
What if you don't find a roof leak? Your best remedy is to clean the entire roof and coat it with a roof coating. This should be done at least once every two years. See our section on coating your roof for more information.
Remove a panel to see if there is a vapor barrier. The vapor barrier could be a plastic sheet, or it could be attached directly to the insulation. The vapor barrier is important because it keeps the moisture away from the insulation.
If you don't have a vapor barrier, you will need to:
The second method is considerably easier than the first, but it is not as effective. If you intend to add insulation above your ceiling or to replace your ceiling panels, make sure you install a vapor barrier at that time.
Other ways to reduce condensation build-up: