There are over 300 million shipping containers sitting, completely empty, in ports around the world. It is too expensive for the country to ship their containers back. It is much cheaper for these countries to buy new ones. The average life of a shipping container in the shipping service is 10-15 years, but the steel frame will maintain strength for much longer. Containers are designed to be weather tight, immune to mold, bugs, and the elements. The steel frame is so strong that they can stack the containers 9-12 tall (fully loaded up to 153,000 pounds). Building with shipping containers has become a popular application all over the world due foremost to their superior strength, and inexpensive costs (some used containers can sell for as little as $900). It also helps to reduce waste and turn that waste into shelter. Containers have been used to construct: homes, hotels, workshops, low income housing, swimming pools, tornado shelters, garages, offices and classrooms.