Polymer modified asphalt waterproofing is applied by incorporating polymers into the asphalt or bitumen during the modification process. This is typically achieved through a blending process where the polymer is mixed with heated asphalt, enhancing its elasticity, adhesion, and resistance to water. The modified asphalt can then be applied as a waterproofing layer in roofing, paving, or other applications, providing improved durability and performance against moisture infiltration and environmental stresses.