Is that Spot on the Ceiling an Active Roof Leak?
Looking at this photo of a stain from a roof leak, it is telling. This photo is showing some brownish color rings with a darker gray color circle inside of them. The darker gray color is also more of a solid circle than the brownish rings. The darker gray color is actually wet to the touch and the brownish color rings are dry to the touch.
Looking at this photo, it is apparent that this leak did not just start and has had some time to create the brownish staining. Since there are several rings, it indicates that it has leaked and dried several times. The brown stain is particles in the water from its travels from the roof, then the deck, then the truss system or joists, the insulation, and then the topside of the ceiling board. In this case, the ceiling is a drop ceiling, which just means it is installed as a system on its own and not installed directly to the roof trusses or joists. This allows for mechanical and lighting items to be installed and serviced in between the ceiling and the roof.
Usually when there is brown staining, it means that the leak is dry or has been dry. It does not mean that there is not a roof leak, but can signify that there was a leak at one time.
Throughout a season, the stain may stay a brownish color until such time the roof leaks in sufficiently to allow the water to make it all the way to the ceiling and show itself. This is when it will turn the darker gray color and signify that it is wet, this would mean that the roof leak is active.
We have run into many situations where there are stains on the ceiling from previous roof leaks and the client will ask, “Is that leak active?” Typically this is a new owner that does not know the history of the home or building. The response is always the same, “Not sure, we will have to wait for rain or water test!” The current or past occupant of the home or building is the person to ask, because they are the person that would be around when it rained to see if the spot turned that darker gray color. If an entire summer season passes and the brownish color stain never changes, then it is probably safe to say that the roof leak is not active.
This is a generalization and does not represent all situations, but is geared towards explaining what color the stain is when it did leak from that heavy rain we got last night. Now this wet area may only last a day or so after the rain stops and then it is back to the way it looked before.