The River Rock Shower Floor is a popular option for new shower floors. It's made of River Rock, which is a natural stone that has been used since ancient times. It's known for its durability and beauty. A shower floor can be installed in any size and shape. The size depends on the space available, the number of people using it, how often they use it, and what other activities need to take place in the shower. The average square footage of a shower floor is about 4 feet by 4 feet.