Principles of Typology 1980s-1990s

In general, modern office buildings tend to fall into three categories: closed plan, open plan, and modified open plan. Selection criteria include:
- the amount of planning flexibility required;
- the amount of visual and acoustic privacy required;
- initial and life-cycle costs

Closed-plan offices have full-height walls or partitions dividing the space into offices with doors. Private offices are typically located along the window wall. Administrative support is housed in workstations along corridors or in shared rooms. The advantages include a controlled environment, security, visual privacy, physical separation, external views, and traditional and systems furniture applications. Disadvantages include lower efficiency than in an open-plan office, lack of flexibility, especially in responding to changes in office technology, the high cost of relocation, restricted individual and group interaction, and the fact that more extensive mechanical systems are required.

In open-plan offices, all workstations are located in an open space with no ceiling-height divisions or doors. Administrative support is located in rooms with floor-to-ceiling partitions and doors. The advantages include efficient space utilisation, greater planning flexibility, ease of communication and lower life-cycle costs. Disadvantages include higher initial costs, no visual privacy, no external views and less environmental control.

Modified open-plan offices combine elements of both the others by positioning certain workstations in an open plan with systems furniture, and others in private offices. Administrative support is also located in enclosed rooms.

Calculations: Construction. The structural members of the building have a strong influence on the possible ways in which an office area can be divided (1) – (4). A clear floor-to-ceiling height of 2.75m permits the later installation of raised floors or suspended ceilings. Ceilings can be 25cm lower if most activities are carried out while seated, but the clear height should not be less than 2.50m. Corridors and toilets can be 2.30m high, but must have space for ducts and pipes. The economic efficiency of load-bearing members depends far less on the optimisation of individual components than on their integration into a functionally efficient building.

Beam systems may be longitudinal or transverse – (1) – (4). This example of the range of design approaches is based on a reinforced concrete floor with a span of 6.50m. The cost and weight of the span affects the choice of supporting structure and foundation. A greater floor thickness has advantages because the optimum rigidity of the structure will be maintained if the loadings vary.

A ribbed floor is economical only for larger spans. Although it is light weight, it costs more for sound insulation. It is not possible to cut through ribs, and openings cannot be introduced owing to the limited space between ribs. Double-T or Pi-shaped slabs or beans are structurally better for large spans. Transverse service ducts should be located in the floor in corridor areas – (1) - (5). The facade plane may be located either behind, between or in front of the structural plane. The maximum flexibility of space is achieved if the external skin is independent of the structure of the building.

With interior columns, cantilever floors (with curtain walls) can even up the loads on the columns. Rigidity is provided by the use of wall plates, multistage bracing, and solid access cores with secondary zones on the ends.

Solid dividing walls can replace columns and main beams in some parts of the structure, and the inclusion of panels helps to improve rigidity – (6) - (8). Fixed openings should be specified in advance to prevent later problems. Lightweight partitions have the advantage of being movable and also permit later decisions concerning the division of space.