Durability

 Buildings are expected to be fully functional for the time period of their service life. While this period is not explicitly fixed in most cases, the usual present expectancy is for a building to last between 50 and 100 years, much longer than is expected from other technical objects. Building structures are exposed to a number of corrosive or detrimental actions which slowly degrade its fabric and need to be dealt with already in the design period, predominantly during the constructional design. Thus, diverse measures of material preservation need to be taken, especially against moisture which is the most hazardous action buildings are exposed to, in particular when certain vulnerable materials are involved like wood or steel. The simplest and most basic measure is to make sure that water or humidity cannot accumulate on component surfaces and is drained as quickly as possible.