Final answer:
IKO Cap sheet flashings should extend at least 8 inches past the 90-degree transition onto the horizontal field surfaces to ensure proper waterproofing.
Step-by-step explanation:
IKO Cap sheet flashings must extend a minimum of 8 inches onto the horizontal field surfaces past the 90-degree transition. This extension is crucial to ensure proper waterproofing and protection at the point where the vertical and horizontal surfaces meet. The specified measurement is based on industry standards and IKO's installation guidelines to provide adequate coverage and sealing.