Serviceability limit state design of structures includes factors such as durability, overall stability, fire resistance, deflection, cracking and excessive vibration.
For example, a skyscraper could sway severely and cause the occupants to be sick (much like sea-sickness), yet be perfectly sound structurally.
This building is in no danger of collapsing, yet since it is obviously no longer fit for human occupation, it is considered to have exceeded its serviceability limit state.
Hence, the serviceability limit state identifies a civil engineering structure which fails to meet technical requirements for use even though it may be strong enough to remain standing.
Building codes tend to be restricted to ultimate limits related to public and occupant safety.