I had a complete re-roof last year from clay tiles to concrete. Does building regulations need to pass the work off and send a certificate? If so, was it the roofers responsibility or mine to contact them?
it definitely needs signing off.
Its the home-owners responsibility to notify but your builder/roofer would normally deal with it. as we are best to notify for any request like added strength, the roof structure will have needed to be beefed up, (normally i don't know the exact situation) but usually, and often this needs or can only be checked before the new roof goes back on. you have added weight.
As for certificate that changes from council to council