Sedum-roof-suppliers-ireland, moy materials is one of the uk and ireland's leading suppliers of high performance innovative waterproofing and insulation systems. providing systems and soloutions to deal with almost every waterproofing condition, moy is the complete system provider for your next project.. The structure of a shallow pitched green roof differs slightly from the structure of a flat roof. because water runs off the roof more quickly, a thicker substrate layer is needed. the substrate gives the correct dose of nutrition to the plants and so ensures your green roof is indeed green.