When I virtually rebuilt our barn many years ago I removed the very dodgy & dangerous pitched roof leaving just the concrete pillars it sat on.
I constructed 8m long beams to span the pillars which I'd reduced in height on one side to give a fall of about 150mm across the width. A new roof was built off these beams using crinkly tin covering which discharged rainwater direct into the garden with no gutters.
One of out neighbours , now deceased, was quite adamant & viciferous that I'd made a huge mistake because the almost flat roof would hold a build up of leaves from the adjacent trees .
Almost 20 years later I don't think I've ever spotted more than the occasional leave remaining on this roof.
