What type of roofing materials can be used in the valley lining of open valleys according to the specifications?

When considering the appropriate materials for the valley lining of open valleys in roofing, mineral-surfaced roll roofing is suitable due to its durability, water-shedding capabilities, and compatibility with various roof pitches. This type of material is specifically designed to withstand the conditions typically found in valley areas, where water runoff can be substantial.

Mineral-surfaced roll roofing is often made from asphalt, which is inherently waterproof and helps prevent leaks that can occur due to the accumulation of water in these valleys. Its installation is generally straightforward, making it a practical choice for proper valley lining.

In contrast, clay tiles, thatched roofing, and straw roofing do not provide the same level of protection or performance in this specific application. Clay tiles, while attractive and durable, are not ideal for valley linings because they may not effectively shed water in the same manner. Thatched and straw roofing materials are generally too porous and susceptible to water damage, making them unsuitable for areas that require robust water management such as valley linings.