This invention relates to a demountable cassette construction system for building a structure comprising one or more demountable cassettes, wherein the or each of the one or more demountable cassettes are attachable to one or more adjacent demountable cassettes via demountable joints, wherein the demountable joints permit the one or more demountable cassettes to be removed from a structure without removal of and/or damage to the or each of the one or more adjacent demountable cassettes.

A shelter includes a floor portion, at least one wall portion having a top wail portion, a bottom wall portion, or both, and a roof portion. Each portion includes at least two panels which are detachably interconnected using female and male bracket elements configured for receiving the panels and including cooperating means actuated by longitudinal movement for preventing separation of the female and male bracket elements and interconnecting the panels.

A shelter includes a floor portion, at least one wall portion having a top wail portion, a bottom wall portion, or both, and a roof portion. Each portion includes at least two panels which are detachably interconnected using female and male bracket elements configured for receiving the panels and including cooperating means actuated by longitudinal movement for preventing separation of the female and male bracket elements and interconnecting the panels.