Refinishing a flat roof calls for Bonar's Enkadrain 3801 drainage mat. With a recycled propylene drainage core, the material features a lightweight filtered fabric thermally bonded to each side. The mat's filament configuration is protected from UV degradation for up to 30 days after installation. For installation efficiency and performance, Enkadrain 3801 is 30% thinner than other mats on the market, and is designed to lay flatter while resisting expansion, contraction, buckling and creasing. The fabric is also breathable to prevent stagnant water underneath. For all these reasons and more, Azek has named Enkadrain 3801 as its preferred drainage mat for use between waterproofing membrane and it's Azek Pavers on flat roof installations. One roll of 39-inch-wide material covers about 600 square feet and costs between $1.50 and $2 per square foot.