I've just removed a massive old rose which has been growing over my 6X4 shed...and i see if i gone through the roof in one place. I'm thinking i need to re-roof the shed o make it water-tight. Is this a big job? Any ideas how i should start to go about re-roofing it? what materials do i need etc? I'm generally good at DIY (have done everything else in the house myself so far...but have no idea about sheds!). Any advise appreciated.