• Collapse Supplemental Coverage is an insurance coverage under the Insurance Services Administration, Inc. (ISO), general and specific forms of damages (CP 10 20 and CP 10 30) building collapse and (since 1995 editions) collapse of personal property. inside a building for certain reasons (such as the weight of snow, ice, or rain). The coverage does not cover collapse due to design error or failure due to poor workmanship or materials if the collapse occurs after construction is completed.