Method for creating a liquid barrier on building sheathing, provides a polymer mixture with beads of uniform diameter, affixes mesh across joints in the sheathing and trowels the mixture onto the sheathing using a straight edge. The straight edge rolls over the beads and leaves the mixture between the beads for creating a layer have a uniform thickness. Before the layer sets, peaks of an inner corrugated surface of an insulation board are pressed into the layer for adhering the board to the sheathing, the inner surface having valleys between the peaks at a distance greater then twice the diameter of the beads. The layer sets to create the liquid barrier and for fixing the board to the sheathing with spaces left between the barrier and the valleys for water runoff across the sheathing.