A drainage and ventilation mat for use in building exterior walls, roofs and basement assemblies that addresses all three of the following major concerns: drainage, cross ventilation/air flow, and compressive strength. The drainage and ventilation mat includes two layers of parallel, square strands that are overlaid at angles to create a diamond-shaped netting of two layers which provides an air space for horizontal and vertical air movement and protects the drainage plane behind it. The mat features a high compressive strength that creates an air space that can withstand extreme construction and environmental forces. The netting is configured with or without a scrim to accommodate a variety of exterior wall, roof and basement assemblies drainage and ventilation needs.