What is the most environmentally-friendly type of roof material to use on a home and why?

A part of guttering has been replaced to a new front section. When it rains, it is now leaking quite heavily in one or two places. Not sure if it’s under or over the guttering, but the water is running down the brickwork, which it never did before. Any idea what the problem might be and how to resolve the issue.

I have just had a new slate roof, but no flashing has been added to the parapet and firewalls. The roofer insists that this is a separate issue and not part of the roof. The firewalls are still leaking and he insists they need to be rerendered at an extra cost. Are parapets not part of the roof?

I live in a terraced house, there is a skew between us and next door. Next door is rented, few weeks ago the landlord said he'd had front skew repaired (we'd seen they'd been getting repairs, no idea what exactly, the scaffolding just appeared one day), the back one needed doing and would we go halves. I asked him to send me the quotes he gets, he laughed and said he'd get his builder to do it. Turns out his 'builder' is a local handy man. I've since had two roofers to look at the roof, the skew definitely needs work, but the 'builder' who did the front skew has bodged it, and carried out work on our roof at the side of the skew, that now needs fixed. Where do I stand on 1) getting next door to pay for putting the dodgy work put right, and 2) stopping them doing any more work on our side of the roof? I'm having visions of coming home one day and them up on the roof without asking again, same as when the front was done!

How can I know with certainty that a new roof ought to be replaced?

I had a roofer inspect a flat roof a couple of months ago, who then made some patch repairs using torch on felt. Another roofer cam to quote for a replacement roof today and said the felt hadn't been torched on properly and water had got underneath the add on section. The felt could be lifted up without much effort and some of the edges on the felt underneath seemed to be peeling away. He then recommended I remove all of the add on felt as this was far worse than just having the felt below it. First of all, how bad of a job is this and secondly, is this likely to have caused any major damage in two months given we've been having a lot of rain? I appreciate any answers and you taking the time to respond.

What is the cause of black and green stains on my roof?

My neighbour is having an extension and just noticed that part of their ridge roof and flashing is sitting on the edge of my flat roof. Is this allowed or do I need to be having words with them?

Do roofers always need a scaffold to access the roof? There's just a few slates loose on the roof and the first roofer we approached said we'd need a scaffold. Obviously, that adds to the cost of a small repair.

In terms of planning permission, does replacing the tiles count as a new roof? Or is it when the whole thing is redone?