I had a new shed built and installed last week.....all good, or so I thought 
I've noticed that over the last few days it's leaking from the roof...
I rang the shed company and he suggested using a waterproof top coat (which I see I can buy on Amazon for about £30)...but that next time he was in my area, he'd swing by and have a look 
Aibu to expect him to come out and fix it? Or is this a common thing I should sort out myself??