Abstract: Paneling of fireproof insulating elements for walls, floors and ceilings, comprises a plurality of metal-sheathed panels in edgewise abutting relationship. The panels are filled with endothermally variable insulating material that absorbs a great deal of heat during its phase change. To permit the panels to be welded together at their butt joints, the panels have double metal walls adjacent these joints, there being insulation within the double metal walls thereby to protect the endothermally variable insulating material from the heat of welding. A semi-solid, flexible insulating composition can be disposed in the butt joints. External insulating paneling, also arranged in edgewise abutting relationship, can be provided, the butt joints of the external paneling being offset from those of the internal paneling.