Architecture / April 9, 2018 / .
The geometry of a building has a major impact on costs. Building morphology is concerned with the size, shape and complexity of the building. This section provides a very brief outline of the principle morphological factors which influence the cost of building work. The reader is referred to the numerous publications which examine this topic in greater detail. The main design factors which impact on cost are: plan shape, size of building, wall to floor ratio degree of circulation space, storey heights total height of the building grouping of buildings.
The factors influencing this decision include: Is the more expensive option a worthwhile investment? If it can be demonstrated that savings will arise as a consequence of incorporating the more expensive alternative, then the client is well advised to choose this option. The quicker the payback period, the more likely it is that the more expensive option will be chosen. How flexible is the client‟s budget to finance more robust, better quality or more economic structures or systems? Regardless of whether the client wants the more expensive alternative he or she may not be able to afford it. Retrofitting, however, is inconvenient, disruptive and much more expensive subsequently. Will the client occupy the building? Clients who develop to sell or lease may be less concerned with the operating and maintenance costs of the facility which will be passed onto the eventual purchaser or user of the facility. Clients who spend more initially will seek to recover their investment through higher rents or sales price. This approach may be adopted by future oriented private sector clients concerned with sustainability and green building issues. What is the life-span of the building? The shorter the planned life span of the building the less appropriate it is to incorporate robust and durable materials and systems.
In general it can be said that larger buildings with simple, rectangular, regular floor plans and elevations will be less expensive per sq.m. of floor area than smaller, complex shaped, curved or angular buildings. Economies of scale apportion fixed overheads to a larger extent of productive space. Simple setting out and buildable solutions encourage greater plant use and generate higher productivity and less waste. Complex layouts and details are slower to assemble and may involve a number of trades with a consequent greater risk of mistakes and defects. The degree of compartmentation and repetition will also affect the overall cost of the work. New building work is considerably cheaper than work of a repairing nature or work in existing buildings. Single storey structures tend to be more costly than buildings up to three storeys high, beyond which point they become progressively more expensive.
Speedy completion is often required on commercial developments. The pressure to achieve early completion intensifies when financing and interest costs associated with acquiring the site begin to mount. Clients will seek the early appointment of a contractor in these situations to enable a fast start up on site and will favour fast track design approaches where the design is developed in parallel with site construction operations. Such approaches risk allowing insufficient time to identify or consider beneficial design options, and may, on occasion, lead to abortive working and losing time. Speedy construction on site often requires accelerated working and shift or overtime payments, more intense management presence, and the use of dependable subcontractors and suppliers, all of which add to the cost of the project. Fast track approaches rule out cost certainty and the client will become aware of the eventual cost only at an advanced stage of the project.