Gunite pools are concrete pools that are built on-site and can take up to two or three months to build. Fiberglass pools are prefabricated ones built off-site that can be installed within two to four weeks. Vinyl pools are made out of a line of heavy duty vinyl and the pool structure is often built out of prefabricated metal or plastic walls. The ensemble and installation process for these pools happens on-site and can take up to eight weeks.