narrower concept basement ceiling Concept cantilever slab Concept composite floor Concept connecting joint Concept flat slab Concept floor scheme Concept floor system Concept incline Concept luminous ceiling Concept massive slab Concept prestressed concrete floor slab Concept recess Concept reinforced concrete ribbed slab Concept ribbed slab floor Concept steel composite floor Concept sub-construction Concept suspended ceiling Concept timber beam floor Concept vault Concept