Permanent actions include the weight of the structure itself and all architectural components such as exterior cladding, partitions and ceilings. Equipment and static machinery, when permanent fixtures, are also often considered as part of the permanent action. Once the sizes of all the structural members, and the details of the architectural requirements and permanent fixtures have been established, the permanent actions can be calculated quite accuratelly; but, first of all, preliminary design calculations are generally required to estimate the probable sizes and self-weights of the structural concrete elements.
For most reinforced concretes, a typical value for the self-weight is 25 kN per cubic metre, but a higher density should be taken for heavily reinforced or dense concretes. In the case of a building, the weights of any permanent partitions should be calculated from the architects' drawings. A minimum partition loading equivalent to 1.0 kN per square metre is often specified as avariable action, but this is only adequate for light-weight partitions.
Permanent actions are generally calculated on a slightly conversative basis, so that a member will not need redesigning because of small change in its dimensions.