hiya lads,newbie here from sunny brum.first question is i,ve just had the front of my garage wall rebuilt and the sides and rear heightened making it 23ft long x 2oft wide.with a height of approx 9ft.what concerns me is the wall is only single skin with a few pillars spaced out.is this safe?second question is whats the best way to roof a 23x20ft sloping garage?i,m thinking of using corrugated steel.but how do i lay the joists out?do i need a rsj to support the joist.and is a rsj safe sitting on a single skin wall?any help much appreciated in advance.cheers