A drainage mat, or sheet drain or drainage board, is a system that rolls out on top of the waterproofing membrane beneath TimberTech Pavers. Its purpose is to protect the membrane and create a pathway for water to escape to the drains. It is used on the majority of waterproofed flat roof applications. Drainage mats typically come in 4’ x 50’ rolls and are 7/16″ thick. They are NOT affixed to the pavers or the membrane—they float between the two. The segments are installed next to each other to cover the waterproofed areas underneath the pavers. We recommend using the Enkadrain 3801 drainage mat for the majority of applications.