Home Improvement Questions? Ask a Handyman for Answers ASAP
Frankly it's highly doubtful that there was ever so much moisture outside that it would lead to persistent damp and then mould inside.It's far more likely that the guttering is incorrectly installed, and water is getting to the wall and penetrating through, or that you have a roof leak.Does this house have cavity walls, or solid? Was any part of the roof disturbed at the time of the work?
Cavity walls makes it more likely that it's a roof leak. It might be nothing to do with the guttering contractor, but unfortunately there are some unscrupulous people who will do a job and before they leave cause a problem that they hope to be called back to fix.If you know anyone who has a drone (with a camera), you could get a good look at what's going on up there.
I should rephrase that. What I meant is that it shouldn't be possible for moist air to be trapped above the soffit. If your previous soffit rotted, it's possible that there wasn't adequate roof ventilation before. If that's the case, then there could now be condensation forming on the top of the inner skin of the cavity wall, and the result of that is kind of obvious in terms of the damp that you see inside.Roofs/gutters are more complicated than most people realise, and it might be that your recent contractor has been inadvertently caught out by an error in the previous/original build.