Final answer:
Perforated foundation drains are surrounded by an approved gravel material that acts as a filter to allow water through while preventing soil from clogging the system.
Step-by-step explanation:
The student has asked which material should surround a perforated foundation drain. Perforated foundation drains, commonly used in construction to prevent water from pooling around a foundation and causing damage, should be surrounded by an approved gravel material. The gravel acts as a filter, allowing water to pass through while preventing soil from clogging the drain. It is essential that the gravel is free-draining, typically comprising washed, uniformly graded coarse sand or gravel. The size and specifications of the gravel may be governed by local building codes or standards.