What material is recommended around a pipe that penetrates an asphalt shingle roof?

The recommended material for sealing around a pipe that penetrates an asphalt shingle roof is plastic cement. This material is specifically designed for roofing applications, offering flexibility and strong adhesion to both the roofing material and the pipe.

Plastic cement is a type of asphalt-based product that can effectively seal gaps, ensuring that water does not leak into the structure through the area around the pipe. It adheres well to the asphalt shingles and provides a weather-resistant barrier. The characteristics of plastic cement allow it to expand and contract with temperature changes, which is essential to maintain its integrity over time, especially in varying weather conditions that roofing materials are subjected to.

In contrast, while silicone sealant and roofing tar are also options used in various applications, they either don't have the specific properties desirable for roofing (silicone may not bond well with asphalt) or are better suited for different types of repairs or applications (roofing tar can be used but is less than ideal compared to plastic cement). Metal flashing can be important for directing water flow but requires additional measures to seal it properly around the pipe, which may not be as straightforward as using plastic cement.