Snails do not grow new shells when their original shell is damaged or cracked beyond repair. However, if the damage to the shell is minimal, the snail can often repair small holes or cracks over time and continue to live.
Snails grow their original shell from larval stage to adulthood. The mantle that covers the snail's vital organs is attached to the shell itself. As the snail grows, calcium carbonate is secreted along the outer edge of the mantle. As these secretions harden, a strong shell is formed. It continues to grow until the snail is fully developed. Often a lip is formed on the edges of the shell.