The significance of cost to the designer has been considered in terms of economy of design. The estimated cost of the scheme should broadly be in line with client’s available budget, and wherever possible, proposals should avoid or eliminate features which are unnecessarily wasteful. At the construction information stage the design team are engaged in producing information to enable contractors to tender for the work, or are part of the contracting team organising themselves to start building. The framework of the building is set, and it may be too late to fundamentally change the design to achieve better economy, but the selection of materials, components, assemblies and finishes is still open to examination and determination, influenced by practicalities, appearance and cost.

In this respect, with regard to economy, decisions can be affected by the costs of supply and construction and the effects of ‘cost in use’.

The costs of supply and construction

Requirements illustrated on drawings and defined in specifications are the starting point, but actually achieving or obtaining them may not be quite so simple. If the design of any element is ‘non-standard’ or ‘special’ it will almost always be more expensive to manufacture adding costs which may or may not be justifiable. Once work has started on site, it may be discovered that specified materials and components are no longer available, or that they cannot be delivered quickly enough. There is a risk of delay while alternatives are arranged adding extra costs for the contractor and client. A particular element of construction might be frustrated through lack of suitable labour or equipment or through particularly inclement weather conditions.These issues must all be considered as specifications are determined, attempting to predict possible difficulties which may increase costs.

The design and specification of some elements in the new building can be governed by consideration of costs over a period of time of use. The period could be the predicted lifetime of the building, 30, 60 or 100 years, or whatever figure is agreed as appropriate. The period could be quite short, 2, 5 or 10 years, a more easily understood target based on present experience. It is becoming increasingly more difficult to predict changes in standards and technological advance which could revolutionise building design. The notion that a building should last for 100 years, even 30 years may soon no longer be as important as it once was. Whichever figure is selected, the initial capital cost can be related to the potential running and maintenance costs to assess the possible financial benefits of more or less investment at the beginning.

For example, consider the design and finish of an internal wall. It could be an expensive, high quality, pre-finished facing brick or stone construction which over a period of say 30 years requires no maintenance or decoration. Alternatively, it could be a very much cheaper concrete block and plaster construction which will require maintenance and redecoration every 3–5 years. The capital and maintenance costs can be compared over the period to see which represents the better value for money. The costs of borrowing must also be included in the equation, adding interest for higher expenditure at the start or saving interest on lower expenditure, but spending money periodically in the future. The assumption in this example of course, is that the wall is to be maintained in its original location and condition. For many commercial buildings, the occupants may wish periodically to reorganise the spaces within the building, or change the appearance of the wall. In such a case, the expenditure on a higher quality of construction and finish may be a disadvantage and represent a waste of money. It may be much more economical to specify a cheaper system which can be easily modified to suit future demands. It could equally be argued that in the light of the need for flexibility, it could be appropriate to use a demountable system for the wall, which could be more expensive than facing brick or stone, but which can be taken apart and reused in the future. It is only by considering the costs over a projected period that a decision can be taken about which one represents the best ‘value for money’.

Other elements will have a more rapid pay back time. For example, an expensive but more efficient heating system can pay for itself within a very short time by reducing energy consumption. The choice of cheaper equipment may not only represent higher running costs, but may lead to more regular maintenance and discovery that it wears out sooner, requiring earlier replacement. The introduction of an automatic door to the workshop, which is an expensive piece of equipment may not only lead to a warmer, happier workforce, but save so much money by eliminating wasted heat that its cost is recovered in savings within 2 or 3 years.

As well as the running and general maintenance costs typical to all buildings, the client and future occupants may be faced with additional costs because of the difficulty of gaining access to carry out maintenance because of the way that elements have been positioned. For example, high-level windows are much more difficult to clean or replace than those which can be reached easily. Changing a light bulb in a fitting on the ceiling at the centre of a large open space could require the installation of scaffolding, and replacing a broken part in aheater located in a tight corner with insufficient working space may take much longer than anticipated. Consideration should be given to the costs of subsequent dismantling and demolition as required by the Construction Design and Management (CDM) legislation. The focus of the legislation is the protection of future occupants and workers from risks to their health and safety, and the cost implications can be significant. For example, the selection of hazardous materials such as asbestos, frequently used in the past is a major problem to any building owner who now finds that the material is in their buildingand must be replaced.