Code
All vertical walls shall have a durable finish suitable for regular scrubbing and cleaning at the waterline.
Annex
SKIMMER POOLS require a six inch (152 mm) to 12 inch (305 mm) high finish due to the varying height of water associated with in-POOL surge capacity of SKIMMER POOL systems. Gutter or perimeter overflow systems require a minimum finish height of two inches (51 mm). If dark colors are utilized for the POOL finish, the POOL finish should not exceed a maximum height of 12 inches (305 mm) for contrasting purposes. Typical finishes include: tile, stainless steel, vinyl, fiberglass, etc.