How can I identify the cause of ceiling water damage?

Question

Just wondering if there is an easy way to tell if water damage on the celing is a result of a roof leak, or condensation build up in the house.

Here are some pictures: https://photos.app.goo.gl/6w9uajoAcbcgYpbT8

I drilled a hole from the bottom and stuck a wire so i can be directly over the damged area.

The worst of it is in the corner but there is a bit of mold along the wall too.

Because the damage is in the corner, its very difficult to see the draywall/roof from the attic. However with the limited pictures i managed to snap it looks pretty dry.

I did order a moisture meter, and plan on testing both sides. Is there any thing else i can look for?

This is an older house, with no kitchen exhaust fan.

Answer 1

Not sure if you removed the insulation to take the pics, but if not then missing insulation will create a cold spot which will certainly exacerbate condensation.

I always start with a thorough exterior inspection if possible (to rule it out), but condensation is extremely common in older homes, especially where a ceiling meets an exterior wall. Poor insulation installation at this point is common (it's difficult for some guys to get it right down to meet the insulation in the wall or up to the wall plate etc. as it's often a small space).

Just be aware that there may be an intentional air gap which the insulation should not block. Venting cold roofs is important to prevent warm air escaping the house and condensing on the underneath of cold roof coverings.

Answer 2

I found using an infrared camera attachment for my phone was worth 10x what I paid for my first one. The flir can identify leaks running down the framework you may not be able to see. I started out with a base model but moved up to a pro model because they were so handy both at home and for work. A flir camera was used to do exactly what you are trying to figure out. We noticed the cold water trail that was hard to see by eye even once we knew where it was. It also shows leaks in duct work, bad connections in outlets and breaker panels (the reason I moved up to a pro model) there are several brands out there but a good base model can be found for~200$. Since you are not sure this may be a tool you can use to identify the source.