What should never be used to penetrate roof membranes or flashing materials?

Using screws or nails to penetrate roof membranes or flashing materials is problematic because such fasteners can create openings that compromise the integrity of the waterproof layers. These penetrations can allow water to seep in, leading to leaks, structural damage, and mold growth over time. Roof membranes and flashings are designed to provide a continuous barrier against the elements, and introducing sharp objects can defeat this purpose.

In contrast, alternatives like staples, rivets, or washers may be better suited for specific applications if they are used correctly and designed to maintain the waterproof integrity of the materials. However, even these options require careful consideration of the installation technique and the type of materials involved to ensure that the roof remains watertight.