Construction in existing buildings has recorded a growing share of the construction industry in recent years. This development was particularly evident in city centers. Building in the existing stock (also referred to as existing construction) basically involves value-preserving and value-enhancing measures on existing buildings.
In the current Fee Structure for Architects and Engineers (HOAI), in§ 2 Para. 5 synonymously of "conversions as redesigns of an existing object with interventions in construction or inventory".