1 Economic Aspects

- Economic buildings should not be confused with cheap buildings. An economic building provides the required standard at the lowest cost. Cost must therefore always be considered in relation to standards and in this context the term costs means costs over the whole life of the building, taking into account running and maintenance costs as well as the initial costs of constructions.

- The basic resources for a building are :

(1) money,

(2) men (women),

(3) materials and

(4) machinery.

Men (women) must be employed and paid, materials must be purchased and machinery must be bought or hired. The manner in which materials are incorporated in the fabric and structure of a building at the design stage and in which materials are handled and equipment deployed on the site or in a factory all affect the degree of expenditure of money and the overall economy of a building project.

1.1 Planning

- Site considerations

- Plan Shape

- Plan Size

- Layout of Accommodation

- Height of Building

- Environment

1.2 Design

- Detailing

1.3 Production

2 PRODUCTION OF COMPONENTS

- On site fabrication

- Off-site fabrication

3 ASSEMBLY OF COMPONENTS

- The process of site erection is in fact the assembly of a great number of components which may be large or small in size and the process it self is significantly affected by variations in shape and dimensions of the components, by the degree of accuracy in setting out the building and by the nature of the joints between the components.

- Assembling prefabricated components - making things fit in an acceptable manner.

- Difficulties arising in assembly can be rated according to the degree of dimensional control required which may be termed "degrees of restraint".

3.1 Variation in Components

- Inaccuracy in workmanship during manufacture (e.g.. mould making).

- Nature of the materials (e.g.. concrete which shrinks or expands).

- To ensure that the components will fit together on site it is essential to (1) relate their dimensions in some rational way, (2) define the spaces in the building in which they are located and (3) control any variations in their size by setting predetermined limits to them.

- Modular coordination - based on the use of a common dimensional unit or "module".

- Tolerance - the difference between the limits within which the size of a component must lie and the system of tolerances provides a standard method of determining the limits of the manufactured sizes of a component relative to its modular size, that is the size of the space within which it should fit. The actual size must always be less than the modular size, the upper limit being determined by the minimum width of joint required and an allowance for positional variation in site assembly. The lower limit is determined by the allowance for variations inherent in manufacture such as twisting, bending, shrinkage. The limit may be indicated either by specifying the permitted maximum and minimum dimensions or by specifying the mean of these with the appropriate plus and minus variations.

3.2 Setting out and Positioning

- Variations in the accuracy of the instruments used.

- Skill and care - Human Factors.

- Inspection and supervision.

3.3 Joints

- The erection process is essentially the assembly of parts put together in different ways to form the total building fabric. The parts meet at joints or connections. In the field of building, joint refers to the space between components whether or not they are in contact; a connection has the added implication that the components are held together structurally.

- For practical reasons joints are necessary between the elements of the building fabric, say between wall and floor, and between components making up the elements, in order to accommodate changes in material or because the limitations in size due to the nature of the materials used, as in bricks, or, conversely, in order to keep the parts to a manageable size. Other joints may be incorporated in order to control cracking due to thermal, moisture or structural movement of the fabric or to permit breaks in the construction process, as in casting insitu concrete.

- The purpose of a joint is to connect the adjacent components in such a manner that, while allowing satisfactory assembly, the functions of the components joined are preserved across the joint so that the functional integrity of the whole element is preserved. Thus the functional requirements of the joint include those of the components such as the provision of adequate weather and fire resistance, thermal and sound insulation and, if it is a structural connection, the ability to transfer forces. In addition, other requirements arising simply from the existence of the joint must be fulfilled, such as accommodating thermal and moisture movements and variations in size and in positioning of the components in order to avoid cutting and fitting on site, and permitting, in some cases, dismantling of the components for possible replacement.

3.4 Types of Joints

- Butt joint

- Accessory joint

- Integral joint

3.5 Joint seals

- There are two types of seals - rigid and non-rigid.

- Rigid seal - formed by gluing or welding the components together and its stiffness requires movement to be accommodated in the components themselves or in special movement joints provided at intervals in the building fabric.

- Non-rigid seal - one which permits movement to be accommodated within the joint itself by virtue of its inherent flexibility.