Function requirement of door

Strength- a door assembly should be strong enough to sustain the conditions of use without undue damage
Stability-A door should not bow , twist or deform in normal use to the extent that its appearance is unacceptable or it is difficult to open or close.
Durability- A door should be constructed of materials that will not wear easily and required minimum amount of maintenance despite heavy use.
Fire resistance-Doors may serve two functions in the event of fire in buildings : first as a barrier to limit the spread of smoke and fire and secondly to protect escape routes.
Weather resistance- As a component part of an external wall , a door should serve to exclude wind and rain depending on the anticipated conditions of exposure.
Thermal insulation- doors , even when closed , can be a major source of heat loss and thus the resistance to heat transfer by both door and frame becomes important.
Sound Insulation- A door should afford reduction of sound for the sake of privacy and for those functions , such as tutorial rooms , where the noise level is of important.
Aestheties- Given the high level of interaction with doors and door openings , it is important that the appearance qualities o the door are considered.
Security-External doors should be designed so as to provide a secure barrier against unauthorised entry.
Privacy-Door should serve to maintain visual and acoustic privacy inside rooms to the same extent that the enclosing wallls or partitions do.