Which component is primarily responsible for waterproof protection in all roofing systems?

The component that is primarily responsible for waterproof protection in all roofing systems is the waterproof membrane. This material serves as the first line of defense against water infiltration, creating a barrier that prevents moisture from penetrating the underlying layers of the roofing assembly. Waterproof membranes are designed to be durable, resilient, and capable of withstanding various environmental conditions, including extreme temperatures, UV radiation, and the stresses of expansion and contraction.

While the roof deck provides a surface for the roofing system and supports all components, its function is structural rather than waterproofing. Insulation plays a critical role in energy efficiency and temperature control but does not serve to stop water entry. The drainage system is essential for directing water away from the roofing surface and preventing pooling, but it relies on the waterproof membrane to keep the internal structure dry before the water reaches the drainage points. Therefore, the waterproof membrane is key in ensuring that the roofing system effectively protects against water ingress.