Is this a problem with my flat roof?

[Noddydog]

About 18 months ago at the corner edge of my flat roof a bubble appeared under the felt. Since the roof was still under a 10 year warranty the roofing company replaced a section of it. You can see it in the photos below where the felt looks lighter in an oblong piece.

All was good until recently when I noticed a dark thin triangular area, like it is damp, along that same part of the roof. On the underside of the roof the ceiling below is currently dry to the touch with no sign of any water staining. However I am concerned that something might be wrong due to the discolouration/staining (in the photos below) on the upper side of the roof.

Can anyone tell me what this is likely to be?

The roof is now outside the warranty period so I want to avoid calling someone out if this is quite normal.

Thanks.

 

[Noddydog]

 

[alan333]

Probably just torch marks from where they re-heated an 'older' roof to fit the new flashing. I wouldn't worry about it.

 

[Noddydog]

Thanks Alan, but it's only appeared in the last few weeks.

 

[^woody^]

It's dirt from the rain water run off

 

[catlad]

Not sure if its my eye's of that new piece is lapped the wrong way?

 

[chappers]

It is but it's not going to matter really and may be why the dirty water is flowing out like that rather than running down that edge.