Underlayment panel having drainage channels

An underlayment panel having a top surface, a bottom surface, and edges, the top surface having a plurality of projections that define top drainage channels, the bottom surface having a plurality of bottom projections that define bottom drainage channels, the edges having at least one standout spacer arranged to form a gap with an adjacent panel, the gap being configured to provide fluid communication between the top drainage channels and the bottom drainage channels, the panel further having a plurality of drain holes arranged on the panel, the plurality of drain holes providing fluid communication between the top surface and the bottom drainage channels, wherein the plurality of projections on both the top surface and the bottom surface have a first spring rate characteristic and a second spring rate characteristic such that the first spring rate characteristic provides for more deflection under load than the second spring rate characteristic.

An underlayment panel having a top surface, a bottom surface, and edges, the top surface having a plurality of projections that define top drainage channels, the bottom surface having a plurality of bottom projections that define bottom drainage channels, the edges having at least one standout spacer arranged to form a gap with an adjacent panel, the gap being configured to provide fluid communication between the top drainage channels and the bottom drainage channels, the panel further having a plurality of drain holes arranged on the panel, the plurality of drain holes providing fluid communication between the top surface and the bottom drainage channels, wherein the plurality of projections on the top surface have an increasing spring rate characteristic from top to bottom of the projections such the upper portion of the projections provides for more deflection under load than does the lower portion of the projections.