I am changing a flat garage roof to a sloped roof by adding joist wedges across the deck, screwed in into the garage joists. While 1/4 inch per foot or more may be ideal, I have 30 feet to go across, and a 7.5 inch taper would require some heavy lumber. I am in Ohio, and I do not know if there really is a minimum slope mandated by the State (or a national standard) or a minimum slope that EPDM manufacturers recommend. I known, for example, that isoboard underlayment comes in 1/8 inch and even 1/16 inch per fooot tapers. EPDM is even approved for flat roofs, I think. A link would be nice. I need to convince the inspector. Thanks all!