The main function of a wall is to provide enclosure to the building: that is, external walls keep out the weather and intruders, and maintain some control over the transfer of heat, light, noise, fire and ventilation. An external wall must be able to resist the wind and seismic loads applied to it, and transfer them back either to the ground or to a separate supporting structure. Internal walls subdivide spaces, and to a lesser extent provide some of these separating functions between various spaces of the building.
If the construction of the wall is suitable, it can also provide some or all of the vertical loadbearing function of the building. A wall which only supports its own weight and the wind and seismic loads acting on itself is described as non-loadbearing. If it also supports loads from the roof or floors of the building it is regarded as loadbearing.
Next section: Loadbearing Walls