The buildability factors are important to be considered in the evaluation.

1.RepetitivenessThis is the main principle of buildability which is agreed by various researchers. It is one of the seven keys concepts which is highly recommended for achieving good buildability design (CIRIA, 1983; CII, 1986; Hon, et al., 1989, Ferguson, 1989). In order to obtain clear information on the impact of repetitiveness on the project, a further breakdown of this factor with respect to the property of the building element is essential i.e. element specification, dimensions and material used.Since each of these properties of the design elements can appear uniquely on the various elements, the evaluation of such properties on construction may be significant.a) SpecificationDifferent specifications for building elements can reduce the speed of construction, as work adjustment will be necessary as the work progresses.Specific measures would be required on some of the element specifications.The buildability scores calculated are determined by calculating the number of building elements that use a particular type of specification and divide by the total number specifications that fall on the group of the element. A lower percentage represents how a small use of the specification in the building elements increases factors for buildability.b) DimensionLike specification, dissimilar building element's dimensions or sizes in a project, is likely to delay the construction activities and increases the cost of resources. Element dimensions can affect the decision on resource allocation since it can directly influence the amount of workload to construct the element. The buildability score on dimension is calculated as a percentage from the number of a specific dimension of the represent the element group, over the whole population of the element class. Lower buildability scores indicate lower factor of buildability as the dimension for the element is repeatedly used in other similar building elements.c) Material usedBy referring to the specification, the exact materials type and attributes are identified. Similar to dimension, the repetition in using materials can effect the allocation or resources on the project as well as the construction activities. The buildability score is determined by calculating as a percentage on the number of a specific material being used for the element group, over the whole population of the element class. Lower scores indicate good buildability as the material used for the element is repeatedly used in other similar building elements.d) ShapeThe shape of the element also contributes to buildability. For a reinforced concrete element, complex shape requires complex formwork thus consuming more time and cost for construction. T shape or L shape, Rounded shape is more complicated to be built compared to just a square or rectangular or a simple shape. Since the shape of an element could not be directly quantified to illustrate its construction difficulty, a general weighting scale illustrating its difficulty is applied in the calculation of its buildability score.For simple square shapes the weighting scale assigned to the element should be higher compared to the complicated shape of an element, either column, beam, slab etc. A default weighting scale is already allocated for each shape which can be changed by user/evaluator. The calculation of the buildability score is determined by the equation below. Lower scores indicate good buildability as the shape applied to the element is repeatedly used in other similar elements.

2. Functional requirementThe functional requirement of a building element indicates whether the element required is part of a structural, aesthetic or services system. The functional identification is normally used to produce a logical sequence of construction. Since structural elements support other building elements, the element is normally given high priority during construction. This functional indication signifies the buildability impact of the element in the construction process. Since it could not be measured, a general weighting scale is allocated to this functional attribute of an element.a) Structural and aestheticAny element in the building has a certain function. In some cases the element could also have a combination function, i.e. structural as well as aesthetic.As a default in this approach, a weighting scale was allocated for each of the functional attributes. As a guideline in this approach, any element which has a single function has less weighting scale, than an element which has more than one function. If an element has more than one function, then the weighting scale for each function of the element will be added to derive with the total weighting scale for the element.The weighting scale of the element is given based on the effect of the element to construction as if it would be decommissioned. For example, alteration of the structure member during construction will obviously affect other elements of the building and could delay seriously the construction progress of the project. If the building element is required due primarily to aesthetic reasons, then the weighting scale of the element will be lower then the structural, since any alteration going will only effect the finished part of the building element.However, if the building element is a structural element and is required to be highly aesthetic then the weighting scale of buildability will be higher than the weighting scale normally used for other structural elements. The same principle also applies to a structural element which is also used as a services element.

3 LocationThe location of the element effects construction work for accessibility of labor, material and plant. Therefore, special requirements would berequired to be considered when selecting the resources. For example, if a building element is located on the ground, its method of construction is different to that located on the seventh storey. The principles of evaluating the location factor is related to how easy the resources could be accessible to the element. If special plant, temporary facilities and arrangements are required to realise the element, then the location is critical in the buildability aspect.a) HorizontallverticalElements situated on a horizontal plane required direct support from falsework or formwork, while vertical elements will require extra strutting and platforms for accessibility of labour or plant. The location of the element, either on the parameter on the inside of the whole building also contributes to buildability.By determining the horizontal and vertical locations of the elements a weighting scale is applied accordingly. This buildability factor does not have its own buildability score, but the weighting scale assigned for this factor would be used to derive other buildability scores i.e. since location effects the use of plant and facility, its weighting is applied to the use of these resources.A default weighting between 0 - 1 is allocated to these factors. Lower scales represent higher locations or far from the building parameter.b) PositioningThe element position within a floor level i.e. near to floor, ceiling, could also influence buildability. For example ceiling finishes which are located under the floor slab of the floor above, would require a platform for the construction activity compared to floor finishes. The positioning of service ducts on the upper part of the wall would require scaffold when assembled, compared to its positioning at lower parts of the wall.By determine the position of the element from its geometric location, a weighting scale is applied accordingly. A default weighting between 0 - 1 is allocated to these factors. A lower scale is assigned to higher positions of the element within the floor level. This buildability factor would not have it own buildability score, however the assigned weighting scale is used in other buildability factors i.e. since positioning effects the use of plant and facility, its weighting is applied to the use of these resources.

4 Trade utilisationThe key concept applied to this buildability element is based on the trades utilisation to construct a building element.a) Trade usabilityThe buildability score for trade usability is calculated as percentage from the number of the trades being used for the class of the element. The lower the percentage of usability calculated, the lower the buildability score associated with the element. For example, if tile finishes are widely used on every floor of the building, then it is likely that the same trade will be used for all the work. If floor finishes differ, then different trades would be required for the finishes work.

b) Trade variabilityThe buildability score for trade variability is determined as a percentage calculated from the number of trades required for the element over the total number of trades for the whole class of the element type. Building elements which require a variety of trades are likely to impose various constraints on the preparation works for the construction activities. For example, a wall element made of bricks requires bricklayers, and scaffolders, while concrete wall will require concretor, carpenters, steel fixers and concrete mixers.From these two types of walls different numbers and types of trades are used.Walls which have less interaction and variety of trades indicates good buildability. From the equation, the higher buildability score illustrates higher constraint on construction from trade variability.

5 Plant utilisationThis factor reflects the impact of design on the building element from the assembling process based on the usage of plant.a) Plant usabilityThe percentage calculated to determine the buildability score is similar to theTrade Usability. If the plant is a general plant, then it will carry a lower buildability score as it can be used by other activities. On the other hand, if the activity required specific plant and only occurred at a certain interval o the construction project, then the usability factor for the buildability score would be higher.b) Plant variabilityThe percentage calculated will depend on the number of plant required to construct a particular building element. The less the variety of plant used to construct the element, the lower the buildability score. For example, concreting activity using a mobile crane, a lorry mixer, and a skip, have higher buildability factor, compared to that of a concreting activity using a small number of plant.

6 Facility utilisationThe factor is applied to elements which use facilities such as falsework andformwork. The formwork or falsework is divided into two, either a standard formwork/falsework (off the shelve) or traditional formworklfalsework where cutting and assembling activity is required. A weighting scale is assigned to each type. A lower weighting scale is applied to traditional formwork, since a longer time, and more space on site are required to prepare the formwork/falsework, besides the need for carpenters and associated preparatory work, compared to standard supplied formwork. The user/evaluator is given the choice to set the general weighting scale for the formwork/falsework between 0 - 1. A higher weighting scale indicates ease of use of the facilities for the construction.a) FormworkIf the building element has a complicated shape. traditional formwork is likely to be used. Standard square, round or rectangular shape, with high repetition normally leads to the use of standard supplied formwork. For traditional formwork the buildability factor will therefore be higher. The buildability score is presented as a percentage calculated from the number of elements that could utilise the same form to be constructed over the rest of element class multiplied by the weighting scale given by user/evaluator. A smaller percentage score reflect higher utilisation of the formwork/falsework. Therefore showing good influence on buildability.b) FalseworkThe above principle can also be applied to falsework. For example, a number of square floor slabs with similar dimensions can make use of the flying form or table form whereas an irregular shape of floors with varied dimensions will normally require a traditional falsework built on site. The buildability score is presented as a percentage calculated from the number of elements that could utilise the falsework to construct a particular element. over the rest of element class, multiplied by the weighting scale given by the user/evaluator. A smaller percentage score reflects higher use of the falsework and would therefore show a good effect for buildability. The buildability score equation is similar to formwork.c) StorageA traditional formwork/falsework requires fabricating, assembling, and cleaning which has to be stored before being reused, while standard components of forrnwork/falsework need space only for cleaning, and can be directly used for other elements without conversion or a major alteration.The percentage area allocated on site for storing the formworklfalsework is obtained as the buildability score. The percentage area allocated on a site is based on site layout analysis application.

6.5.7 Assembly buildabilityThis factor represents the conversion factor of the building materials to realise the building elements. It consists of materials, components and subassemblies.The lesser the constituent of this factor in a building element, the lower the score of buildability.a) Onsite/OffsiteThe terms on site or off site represent whether the building element is likely to be prepared on site from basic materials or ready made in a factory and delivered to site for assembly. If the building element is prepared off site, then the process of construction is made simpler as the element is just required to be assembled into the structure. If on site activities are required to convert the building materials then, other factors such as space, storage, access of plant and labour, etc. will be required. It is therefore likely that an off site approach will give less of a problem on buildability, compared to onsite. A default weighting scale between 0-1 is assigned to both the construction approaches. Lower weighting is allocated for off site methods compared to on site.b) Dry /wet processWet construction processes such as concreting, plastering etc., delays successor activity, requires longer construction time, requires extra resources and space for material conversion, etc. Dry construction processes however, are associated with less buildability impact on construction compared to wet processes. To reflect the buildability impact of these two processes, the user/evaluator would have to set a weighting scale for these processes which are allocated between 0 - 1. A lower weighting scale indicates a higher buildability impact. This buildability factor does not have its own buildability score, but the weighting scale assigned would be used in other buildability factors i.e. process flow factors.c) Number of assemblyThe buildability score of this factor depends on the number of assembly or construction processes required to form a building element, the higher the number of assemblies, the higher the value for the buildability score. For example, a brick wall requires laying bricks and mixing mortar. while a concrete wall requires building formwork, fix reinforcement and concreting.It is obvious that building a wall of concrete will take a lot more resources and time for assembly. To reflect this buildability impact, the buildability score is calculated based on the percentage of number of assembly. for an element over the maximum number of assembly occurring on the same class of element.8 Element buildability dependencyTo form a complete building, all physical building elements have to be connected to other elements. Topological relationship types. represent the relationship between the building elements. The relationship reflects the process or procedure for constructing the elements. For example, supported_by relationship, indicates that the supported element can not beassembled unless the supporting element is built first. Other relationship type such as, attached_to , embedded_in, covered_by, connected_to. etc., all carry a different impact on the flow of construction activity (section 6.3.1.1)a) Topological dependencyThe weighting scale applied to this factor depend on whether the dependen element are structural, services or architectural elements. A building element dependency which is based on structural reason is expected to have the highest weighting scale compared to other elements which have alternative reasons for attachment, such as embedding conduit to a wall or floor, etc.Other relationships such as attached_to, embedded_in, or covered_by range from low, moderate, to a high buildability weighting scale.The allocation of this scale depends on whether the dependent element is an architectural, structural or the services element. For example, an architectural element of a plaster finish which is attached to a partition wall should have a higher weighting to that services element, which could be attached to other elements. The weighting scale assigned to this buildability factor would also be used to calculate other buildability scores i.e. process flow. The topological buildability score is calculated as follows:b) Process relationship typeThe factor defines whether the successor and the predecessor of the construction activities are wet and wet, dry and dry, wet and dry, etc. For example, concreting a slab is a wet process. Since concreting is a wet process. a certain amount of time has to be allocated to let the structure hardens before another successor activity can commence. However, if the element required a dry process in both succeeding and predecessor activities, the construction work can continue without interruption. Therefore, dry and dry relationships would show a low buildability score, while wet and wet has high score for buildability. Both weighting scales for the processes are added and multiplied by a 100 to obtain the percentage. Higher buildability scores would indicate that the element would take a considerable time to build.c) Trade flow relationshipFrom the developed construction plan, all the construction activities and the required resources are interconnected based on the dependency factors. If different trades are required between the predecessor and the succeeding activities of an element, then the factor of buildability is high. On the other hand, if the same trade is used to construct the succeeding element, then the buildability impact would be low since there is a continuation of trades usage.The buildability score is determined by calculating as a percentage the number of similar trades to be used for both successor and predecessor activities, divided by the total number of trade for both activities.

d) Plant flow relationshipThe same principle applied for a trade flow relationship will be used for the plant flow relationship.