Final answer:
Valley flashing for wood shake roofs should be made from at least No. 26 gauge corrosion-resistant sheet metal to effectively channel away water and protect the roof from water damage.
Step-by-step explanation:
For wood shake roofs, valley flashing shall not be less than No. 26 gauge corrosion-resistant sheet metal. Valley flashing is an essential component of a roof designed to collect and channel away water that flows down the valley where two roof planes meet. This metal flashing must be durable to sustain the harsh weather conditions and prevent water penetration that can lead to roof damage.