Abstract: Methods and devices for drain assemblies including those for building into a floor. Such drain assemblies including a drain body which can be built into the floor and which has at the top an inlet zone with a periphery, a peripheral flange with an upper surface, extending substantially in a horizontal plane from this periphery, a water-sealing layer arranged adheringly on the upper surface of the peripheral flange, a sealing mat with the form of a frame with an inner periphery fitting around the periphery, wherein a portion of the sealing mat overlaps at least the outer periphery of the water-sealing layer, and wherein the sealing mat and the water-sealing layer are adapted to be water-sealing and to adhere well to tile adhesive.