Roof problems - leaking or condensation?

[jessicarobin]

Yesterday I went up the loft and noticed that I have some wet patches on the loft floor, looked up and noticed that black roof felt is wet with watery residue, looks like dew or condensation, it obviously drips as the floor was wet. Please someone, who had a similar problem with the roof - can you give me any ideas what it might be, roof tiles or just a roof felt? And how much it would cost?

[Ron_CA]

Will need more information. Is this after a rooftop solar installation? What kind of roof do you have? Tile? Composition shingles?

[Mike90250]

You need to check with a local roofer. To me, it sounds serious. Lots of potential for mold and dry rot.

If it was raining I'd say it was a leak. If it was not raining, I'd suspect condensation. Call a local pro. Solutions include ridge venting, soffiit vents, insulation, and of course, new roof. But this is out of my field.

[inetdog]

You need to check with a local roofer. To me, it sounds serious. Lots of potential for mold and dry rot.

If it was raining I'd say it was a leak. If it was not raining, I'd suspect condensation. Call a local pro. Solutions include ridge venting, soffiit vents, insulation, and of course, new roof. But this is out of my field.

Prime smoking gun for condensation is a bathroom or dryer vent (or even stove hood vent) that ends in the attic instead of going out through the roof. (Thank you Mike Holmes.)
That was never allowed by building code, so it would be the result of a really cheap contractor or a DIY installation by a previous owner.
For a slanted roof, drip trails on the roof usually spell leaks while uniform wet areas usually come from condensation. YMMV.