wood rot

Wanted to get an idea from experts/people who have dealt with what I presume is dry rot in a friend's house. Posted pictures, one from August and a comparison to now where it seems to have gotten significantly worse. It's downstairs, there's no immediate current source of moisture outside...

All, I have an old detached red brick house that has suspended flooring and there's water related issues in the middle section either side of the front door. Outside: concreted upto the front door and either side landscaped. There are low air bricks. Guttering is not leaking and running...

Hi Today I have been investigating some damp plasterwork in our 1920s semi-detached house. We have what looks like a uPVC front door fitted by an owner before us and on peeling back the PVC surround I can see a rotten piece of wood on either side of the door frame (bottom right of the attached...