Building information models (BIMs) are digitalized and virtual graphic representation of buildings, and have found great use in the architectural world, being promoted even by organizations such as the charter for construction and engineers. In fact, many construction contractors and estimators have embraced BIMs to help in estimation of costs for building a house or other structures. One of the reasons that the BIMs have been more significant in estimation of construction costs is the simple that it is in 3D and therefore gives an accurate data as much as it saves the taxing work that would be involved in extracting the same information from the 2D structural plans that have been used traditionally by architects. This means that using BIMs in estimation helps the architects in hitting two birds with one stone. This includes reduction of time required to take estimates for a construction, and subsequently, the estimation costs. The use of building information models (BIMs) is evolving as an important tool in the building and construction industry. It is however important to point out that estimation is not as quick as it sounds despite the fact that the model is highly automated. This follows the fact that architects still have much to do and calculations for adjustments depending on the specific project conditions. This therefore suggests that there is need to improve even further the estimation process of BIM. To understand this, one has to look at the mechanisms of estimation using the traditional methods. To answer the question on the effects of complexity in estimation, a research was carried out on three case studies. One of the studies involved using a non complex and a complex project and employing the use of traditional estimation methods and then in the third case, a non-complex project is used, only this time BIM estimation was employed. The paper carries close evaluation of the cases, analysis and a conclusion that show the implication of complex projects and the use of BIMs.
In the first chapter, a discussion that summarizes the theory surrounding the estimation process in building and construction is delivered. The chapter divides the discussion in three main groups. The first is describing the estimation process in genera, which means describing it without separating traditional estimation methods from use of BIM in the exercise. Secondly, the chapter offers a discussion which offers an insight into the project complexity features and their effects to costs estimation exercise. Lastly, the chapter offers a discussion of on the use of BIM in estimation process. To cap the chapter, a discussion of the three topics in relation to each other is introduced in a bid to help understand the research contributes to the theories.
Cost Estimation Procedure
Estimation of costs involves looking into the future and evaluating different factors and therefore come up with a projection of costs and resources that may be required to carry out a certain activity. In this case, estimation will be for costs of materials and resources. It is one of the most important parts in a construction if success is to be realized. Apart from this, there are other uses of estimation which includes examining the economic feasibility of a project, evaluating project alternatives, offering a guideline to project budgeting and acting a s basis for project cost and schedule control. It is worth mentioning that all these are aimed at determining the profitability of the project.
Due to the nature and the importance of the activity, estimators do not just haphazardly conduct the exercise but follow a certain procedure. The steps that are followed by estimators includes breaking the projects into many cost centers and then estimating the quantities required for the cost centers which represent the end product. This is usually referred to as quantity takeoff. After this, the price tag is put on each individual quantity from the quantity take off by use of historical data, vendor quotations, catalogs from suppliers and other sources of pricing information. Lastly, the product of the quantity and units is conducted and the n a total of the cost centers is done including profits, overhead costs and risks. The importance of breaking down projects into cost centers is that it leads to formation of a work breakdown structure that is used in restructuring and controlling information. Note that the manner in which estimators carry adjustments in their estimates is purely personal with each having preferences. There are many factors that can influence preference including use of the estimates, tools used in estimates, for instance software, data available, the level of project definition, and more importantly, the complexity of the project. The importance of the complexity of the project can only be understood by first understanding the project and complexity. This has been explained in the discussion below.
Complexity is not a constant but rather a function of several features. In construction, the complexity of a project is based on three main features organizational, resource and technical complexities. Organizational complexity depends on the number of people, departments in an organization, or number of organizations involved in the project. Subsequently, resource complexity refers to the quantity and amount of resources that are required. These are assessed by using the budget of the project. Similarly, there is technical complexity which depends on the innovation and technological advancement that is to be used in effecting the project. It is important to keep in mind the fact that this is quite different from human resources as it is indeed an interface of parts and the end product. The three have a potential for affecting and influencing estimation of costs either independently or as a whole unit. Organizational complexity may attain this through loss of information, some of which may be vital. Additionally, estimators may be working simultaneously in the same project and therefore if there is no coordination there are discrepancies in cost estimates. On the other hand, resource complexity increases the amount of work needed to carry out estimates, subsequently increasing the propensity for making mistakes. Last, but not least, technical complexity provides and room for estimators to make manual adjustment in a bid to come up with more accurate estimates. All these affect the final estimate figures. In line with this, building plans that are more complex has more effects from technical complexity as more designs and models will be made during the estimation process. From this discussion, it is evident that there are two main factors that influence estimation procedure in the more complex projects. This includes the need for coordination of the human resource, which is in high demand, and preparation of the structure of estimates. The other major factor is the fact that as complexity increases, more efforts for acquisition of the estimate is required and also the increase in probability of making errors.
Cost Estimation Using BIM
As has been described in the introductory part of this paper, the Building Information Model (BIM) is a virtual, computer-generated model which has been programmed data and designs that can be used in supporting the construction and the resources necessary to completion of a building. There has been noted increase in the use of BIMs as has been stated previously due to the reasons mentioned above. There are however many other benefits of BIMs that have drawn architects and architects towards the technological development. These benefits are laid down in this discussion to expose the potential that BIM has on the improvement of cost estimation in project executions. Furthermore, the discussion also covers the effects and influence of BIM on the estimation process of in project management. Due to this, there is also discussion on the procedure of estimation using BIM in order to experience the difference that it has in estimation process.
Quantity takeoff mentioned earlier in the paper is the main area where the benefits of BIM are realized. This follows the fact that the BIM offers estimators an option to extract cost estimation information using application software besides providing a platform that can support estimators in all design phases. These depends on the phase of development in the construction where in the initial phase BIM can be used in producing quantities information such as volume or the area covered. Note that these quantities have great potential to produce highly accurate estimates. On the other hand, as there is increased progress, the model becomes more detailed and therefore can offer information pertaining to independent parts of the construction such as beams, columns and other parts of the building model. Apparently, the details also become part of the basis for further accurate estimates which comes in handy in the later stages of the project. It is important to mention that the BIM carries applications that can enable the estimators to calculations of components, the volumes of spaces and areas that are covered by the spaces, quantity of materials and all these reported in various schedules for action. This greatly reduces the laborious tasks that the extraction of this estimation would have taken an estimator from a 2D design. Additionally, improvement has found that it is very possible to link the estimating software and the quantity takeoff automatically so that the final product and sum total can be generated automatically, easing the exercise even further. However, like everything else, the BIM has three main consequences to estimators, acting as leverage to all the benefits that it offers. These consequences are the need of the estimators to align data, such as forming a price catalogue, and quantities extracted from the BIM, note that quantities that are extracted from the BIM are quite different from those that the estimator would extract using traditional methods owing to the fact that traditionally estimators have used personal means, sometimes with preferences. The other consequences are that the estimators require choosing time as for optimization of other factors including subcontractors’ alignment, competitive suppliers and other professionals. Lastly the estimators have to device their own means of accounting for special designs and other aspects and feature in a construction that BIM software may not be in a position to identify. Basically, these are the three main drawbacks of using BIM in cost estimation although they are greatly outnumbered by the benefits that the estimators reap. It is important to note that this may have serious implication in a complex project with so many unique designs because of the simple fact that the software cannot detect this uniqueness.
Theory of the Research
The discussion have shown the effects of BIM in cost estimation, indicting that there are two main benefits including the possibility of producing accurate estimates automatically and ability to form a link between estimates and the corresponding costs. Additionally, the paper has indicated that there are three features of complexities that have direct influence on cost estimation. Theses are the basis of the research theory which seeks to evaluate the importance of BIM in estimation process. It demands that one should understand the estimation processes complex projects by use of non-modular structures and then replacing these with BIM based estimation. It is important to note that the research is based on project complexity and BIM use in estimation, suggesting that the cost estimation process must be reviewed severally in different conditions.
All the activities that conducted throughout the research are basically for evaluating the effects that project complexity and BIM use have on cost estimation process and in lieu of this, establish the important aspects of BIM based success in cost estimation. Therefore, the activities seek to answer the question, what are the effects of project complexity and the use of BIM on the estimating process? However, this is only the main research question that can as well lead to some other minor questions such as seeking to establish a relationship between the effects of project complexity in traditional methods of estimation, bearing in mind the structure of and methods of estimation, differences between traditional and BIM estimation and also important features of BIM in estimation. These questions cannot be answered without using tangible evidence and therefore the research answers the research by employing case studies. Three case studies were chosen for the exercise and a certain order was followed in their evaluation in that when the first case was done, a decision was made on which should be the next, thus enables researchers to choose the best cases for answering the research question as well as the sub questions of the research.
The cases that were used for the exercise, three, were all parking structure projects, with the differences being complexity levels and the methods used by estimators in cost estimation. The reason for choosing projects that were similar, parking structure projects, is that it gives an ease of comparing and making out the differences between the cases. Note that they were studied by the use of the documentation including project definition and the drawings used for cost estimation, and hence the results for the estimates. It is also important to point out that there was a need to acquire first hand information from estimators, and therefore an informal interview was also included in the research exercise. However, the main research objectives were met through day to day observation in Ballast Nedam Company. The importance of all these processes was to enlighten on the estimation processes and help the researchers to understand the implications.
In cases evaluation, estimation process is discussed from the beginning to the end, and more importantly by focusing on the steps, people and estimation methods involved. Additionally, analysis of complexity features in projects was conducted by use of project specifics aspects, listing all the differences and similarities, which came quite in handy in helping to understand more sophisticated processes studied.
Company Description: Ballast Nedam
The company is a big one and has two main parking structure projects. These are modular and non-modular. These are handled by the infrastructure division of the company. Note that Ballast Nedam modular structure was developed in such a way that it was easy to dismantle, and therefore, the company can use parts of the projects in other projects as well. The difference in complexity between modular and non modular parking structures is as a result of use of standard elements. All the three cases were chosen from the company and therefore it was easy to create a comparison of the estimation processes in all. The non-complex, modular parking structure with the traditional estimation methods being employed was the first case, and it was crucial to begin with as it helped in understanding the process of estimation. Moving on with the research, a more complex parking structure project was used, but it still involved the use of traditional estimation methods. On the contrary, the third case, which was the only one that employed the use of BIM, was not complex; it was, in fact similar to the first case, only the traditional methods were replaced with BIM-Based estimation. This was to enable the researchers to make a clear cut comparison between traditional methods and BIM based estimations and outcomes. It is also important to point out that there were several sittings by estimators, modelers and supervisors which involved integration of BIM in cost estimation. This was an added advantage in the research as findings concerning the issue were discussed with the people involved and professionals who understood both processes fairly well.
This discusses analysis of the cases resulting to research on the case-studies. One thing that is important for this is contextually addressing the parking structure projects to help in understand what it refers to. Secondly, the three studies are discussed addressing traditional estimation methods in modular structure, traditional methods in non modular and complex structure and again the use of BIM to replace traditional methods in estimation.
There are a number of factors that determine the shape and form of parking structures including the number of parking space to be facilitated by the structure, maximum height, construction regulations and guidelines and accessibility to the roads. Structurally, parking structures are basically the same. Prefabricate elements such as steel or concrete columns are and floors are the most common materials used in the construction of the structures.
CASE 1: MODULAR PARKING STRUCTURE PROJECT AND TRADITIONAL ESTIMATING PROCESS
Modular parking structures contain standard elements, such as columns and floors. From the beginning of the project the estimator has a considerable knowledge of the structure and can extract quantities by counting the number of quantities. Since the structure is a simple one, there is no possible potential for miscalculations and errors of omissions. The estimators in this case create a detailed estimate to facilitate reusability and accuracy, and due to its simplicity the estimators can use old estimates. It also offers the time to estimators to prepare orders and price optimization.
The input that was used in this exercise consisted of documents that had general requirement and designs in two dimensions as well as the surroundings and fire rating. The first thing that the estimator does is to analyze the input, going through all relevant documents and summing up the total incurred costs. To achieve this, the estimator uses a work breakdown structure (WBS) with coding to all corresponding structural parts. Further more, the estimator divides the projects in different levels with the highest level being the end product which is the modular parking structure. The estimator also establishes a system breakdown structure (SBS) that forms the basis of WBS. Note that the main difference of SBS and WBS is that there are activities instead of objects for WBS. The converse is also true for SBS. It is worth mentioning that each object or activity has a unique code that the estimator uses in the process.
Quantity extraction depends on two main processes which include quantity takeoff and work assessment. In physical items, the estimator extracts manually quantities from documentations of the projects which includes drawings and counts each item. However, in more complex structure, extraction is done by calculating the entire part of the structure such as a column. On the other hand work requirements determine evaluation of the total number off hours that is needed to complete the process. This involves a determination of the quantity if parts, for instance floor, would be completed in an hour, and it requires managerial and engineering skills. The scheduler accounts for time while estimator accounts for costs, calling for coordination between the two.
Extraction leads to determination of prices where the estimator uses prices from the company or catalogues from external suppliers. In the case study, the purchaser provided the pricing information to the estimator who had requested for it as soon as quantity takeoff was conducted. The estimator then made a comparison of the prices with the initial estimates. It was beneficial as it offered a chance for the estimator to determine the authenticity of the documents used in the company and also the estimator can source for the cheapest subcontractors and suppliers, decreasing the overhead costs. Armed with this, the estimator then went ahead to make an estimate and accounted for benefits, that were increased accuracy, flexibility of adjustments and potential for estimate controls.
After the estimator had finalized with estimate formations, accounting for contingencies and profit margin for the company started. Since the estimator was certain that the estimates were correct, these calculations were done with a certain percentage. The end product of the exercise is that the estimate bids, schedule and design and tender documents.
CASE 2: NON-MODULAR, MORE COMPLEX PARKING STRUCTURE
In this case study, the effect of the complexity of a project on the estimating process was studied. A larger project was chosen. In fact, its budget was six times higher compared to the previous case. Some practical difficulties were encountered in this elaborate parking structure case study. The project involved design and construction contract both of which were responsibilities of the contractor. Basically, the architect was charged with design delivery while the constructional design was the responsibility of another company. These entities worked together to deliver the requirements of the desired design and also determine he quantities needed to produce the design. This differentiates this case study from the previous one in which only a single entity was given the entire responsibility. The previous case study demonstrated increased complexity in all the features in question; precisely technical, resources-wise and organizational complexity. Most notably, organizational complexity was actually more dominant than any of the others. This was mainly noticed throughout the estimation process particularly in the first three stages of the traditional process of estimation. Each part will be explored comprehensively in this section.
At the initial stages of the estimating process, a detailed design was not ready. Moreover, some parts of the structure such as drawings were also unclear. A comprehensible overview of the design is unavailable as well. A lot of effort had to be put into communicating with other relevant parties regarding aspects of the structure such as changes to be made in design, choosing the appropriate drawings and which qualities should be extracted. All these translated in increased organizational complexity which in turn multiplied problems encountered in the creation of a good estimate and the amount of effort put into it. In this regard, many unforeseeable things are bound to occur and the solution might fail to meet the targeted business needs.
The approach used by the estimator to extract quantities is reflected in the organizational complexity. In the first place, a delay in quantities’ acquisition may result from this complexity especially due to the time wasted before the designer sends the final accurate drawings. The effect of this delay is that the time available for pricing and optimization is shortened since the project team has to stick to rigid tender deadlines. Moreover, there is a higher chance of making errors and some parts may be overlooked as result of this complexity. Therefore, the estimator was made to put more effort in order to acquire the required quantities. General things like steel structure and shape facades had to change forcing the estimator to repeat the estimation process for these parts appropriately in the project. Due to designs that are not clear, an overview of the project was unavailable. For instance, the party given the responsibility of constructional designs only availed sketchy designs making the estimator make a lot of guesses in extracting quantities. The size of the project also increased resource complexity and the costs incurred were six times more than the other case study.
Only a few days were allocated for cost optimization. Therefore the estimator requested for crucial elements that could be extracted more quickly. These are such as electric installations and other concrete elements. Relative to the previous case, fewer prices were requested by the estimator with the most likely reason being that most companies lacked proper time for making suitable offers. The consequence is that the estimates made based on company records rather than on the prices of suppliers and other subcontracting companies. If the estimator was uncertain of the quantities, the quantities would be adjusted to account for the possible uncertainties. For instance, steel quantities were rounded up to increase the cost per unit kilogram. However, in the second study, extra margins were frequently considered as opposed to the first case study.
CASE STUDY 3: BIM COST ESTIMATION
In this case study, a project for BIM cost estimating was studied. It was a pilot project that involved a modular parking construction as a simple and comprehensible model. The results inferred from this case study inferred were similar to those obtained in the first case study. BIM-based estimating process was envisaged on the basis of this project and discussions from peers and other involved parties. The key parts of the BIM estimating process will be explored in this section. The benefits and challenges will be presented in this respect. The figure below demonstrates the use of BIM in the process of estimating.
Apparently, there are four parts in the process just like in the first case study. Some differences exist nonetheless especially due to the modeler, which comes as a new role that increases organizational complexity. The input was however similar in both cases particularly in the 2D drawings and other varied requirements.
General requirements were analyzed first including 2D drawing and other initial documentation. A WBS was established for the specific project which was similar to the one established in the first case study. The drawings were analyzed and the design evaluated easily and correctly. This was done by the modeler whereby a model could easily be created. This is because the model had four different floors and six different columns.
To acquire an appropriate estimate, the estimator had to determine the extent of detail required for the BIM and the quantities to be extracted from it. For this estimate, several types of quantities were needed which were not automatically extractable from the BIM. For instance, the number of parking parlors in each floor element could not be easily extracted from the BIM. The only way to extract such quantities was for the modeler to ensure that the information was extractable. This could be achieved through the addition of shared parameters into the elements of the model. More importantly, the estimator had to know about the quantities that needed to be extracted such as the lengths of each column. Finally, both the estimator and modeler had to collaborate and discuss the WBS specific to the project. The importance of this was to make the estimate acquire a build up similar to the project WBS. WBS makes enables the estimator to make usable estimates particularly for the purpose of cost control. Consequently, the modeler had to employ WBS coding in order to achieve these requirements of the BIM.
Communication was vital between the two particularly about the detail level of the chosen model. Hence, the modeler and estimator chose to leave out foundation piles and electrical wiring. For these areas, alternative approaches were used in contrast to what was used in the first two case studies. Furthermore, a possible overlap of some components of the structure had to be discussed and the WBS well communicated. In this respect, several steel columns would be used for main parking construction or in the stair-casing section. This communication ensured that the WBS code was in tandem with the desired structure. The expected outcome of the model was also communicated between the estimator and modeler. Any properties or parameters added to the same were adequately communicated in good time. For instance, an extra parameter was added to the floor components by the modeler to facilitate extraction of the number of parking places. Finally, a coordination of the digital extraction of the appropriate estimation quantities with the modeler was made the responsibility of the modeler since the estimator lacked the appropriate software for modeling the BIM.
This part was approached just like in the traditional process of extracting quantities. The assessment was still performed in the traditional way and the estimator based the 2D drawings and documentation on this principle. First of all, the estimator adjusted prices on the basis of this assignment. In fact, recipes were prepared using the traditional process since it was the same as the project in case study 1. Estimating software was used to bill the quantities automatically so that recipes corresponded with prices. After the estimator checked the appropriateness of the quantities, they were extracted. However, the modeler had to add the total structural area to the model in other parts of the project. Fences and railings had to be added later. Other changes were added to the BIM accordingly as they occurred.
An estimate of the recipes was acquired alongside the quantities extracted from the BIM. This was based on the estimates of case study 1 whereby new quantities that were extracted earlier were filled accordingly. The estimator made the changes in recipes parametric which resulted in a significant change in the amount of resources and costs prior to the changes in quantities. The figure below gives the correspondence relation between the objects of a BIM and costs.
Fig 2: correspondence of BIM objects with costs
The principle employed in relating objects of the BIM model to costs is demonstrated in the figure as depicted in case study 3. However, the estimator could not give any requests for prices since the project was only in its pilot phase and no tenders for jobs were involved. In the case of a practical and real project, the estimator would have to request for prices in a recipe while keeping it parametric. Furthermore, the requested prices in the final estimate would be used instead of the initial price of the BIM estimate. This would save time as there would be no need for changing a specific recipe.
Three case studies have been explored and have presented various aspects from each study. A comparison of the cases reveals more complex estimates especially in the BIM-based estimating process. Estimating is a core company process and is related to other processes in a company as well. The use of a single standard, WBS, made it even clearer. For instance, WBS was used in various processes including planning, estimating as well as cost control. This is a vital relation that should be considered by companies during discussions related to BIM-based estimating methods. The most important link in this regard is three-fold: BIM, estimating and cost control. Putting case 1 & 2 in comparison, two apparent differences can be noted. In the first place, total time used in acquisition of an estimate was more in case 2 than in case 1. Furthermore, the time allocated for pricing and optimization also varied from case 1 through to case 2. It was also difficult to analyze documents and to extract quantities in case 2. This was difficult and so time taxing especially due to organizational complexity.
Case 1 and case 3 had even greater differences. Case 1 was a traditional estimating process while case 3 was BIM-based. The latter was more time taxing than the former. This can be attributed to the fact that the estimator and the modeler had to work in cooperation and coordinate their actions. However, it was a successful cooperation since the estimator was able to extract quantities thanks to the coordination. Effort-wise, the traditional estimating required the estimator to work a lot more by manually calculating the required quantities. BIM creation is however a new part of the estimating process that has several basic requirements. These include the addition of WBS code, additional parameters and extra objects as well. Coordination between the modeler and estimator is also a requisite.
CONCLUSION AND RECOMMENDATIONS
The process of estimating is a vital company process that relates to other key aspects of a company’s projects. In this report, three case studies have been used to envisage the use of the WBS standard. This standard was used in different processes by the company including planning, cost control and estimating. The most important aspect of this correlation is that it should always be considered during discussions in the estimating process especially in the BIM-based scenario. Essentially, the fact that estimating, cost control and BIM are linked is of critical importance. From case study 1 and 2, the important impacts of complexity features on the process of estimation were found, each of which have specific effects. From the perception of estimating, two important effects were deduced. These include shortage of information required for estimating and the increased difficulty in calculating quantities as well as increased chances of making errors. These effects were handled by the estimators by putting more effort in the acquisition of the needed information and in the addition of extra margins in the estimate. For instance, extra margins were added in increasing quantities, unit pricing, and work rate as well as risk margins among others.
BIM, on the other hand, had its effects on the estimating process. In fact, these are much similar to the traditional process especially due to the similarities in the basic steps followed in the analysis, quantity extraction and pricing of the estimates. The most apparent change in the BIM process is the introduction of the modeler into the process which served to increase the organizational complexity. In essence, it is a fundamental requirement that the BIM and project recipes be aligned beforehand prior to acquiring the estimates. Consequently, the modelers and estimators are required to cooperate and coordinate their operations if appropriate BIM estimates are to be realized. This coordination is very essential as it guides them on knowing which estimates are targeted from the suitable recipes. Moreover, the recipes have to be kept parametric so that the costs can change automatically with any changes made in the design.
As evident in earlier case studies, a shift in workload is noted. It is recommended that the estimating process be improved by reducing the effort made in using BIM to obtain accurate estimates. This can be achieved by structuring the modeler-estimator coordination as well as in the BIM and the estimating recipes. This would need a standard structure of work breakdown, standard detail levels for modeling and estimate with respect to each type of project and lastly, proper documentation of information required. This research was limited in certain aspects. For instance, it was impossible to study a complex BIM project which would enhance my findings in the effects of project complexity. It was also difficult to determine all the advantages and detriments of using a normal BIM process in estimating since case 3 was only a pilot project based on BIM estimating. Moreover, it was not easy to evaluate different ways of creating the recipes which is important in eh BIM process of estimating. These challenges may be eliminated in future studies if more experience is applied and a more complex BIM project is studied.
The key objective of this research was to understand the effects of project complexity on the estimating process in varying project scenarios. As such, the effects of project complexity were summarized using BIM on the estimating process which increased the understanding of estimating process. This knowledge can be used in further research involving more complex projects. BIM is a relatively new approach towards building and construction and this research can be used in evaluating various aspects of current practices employed in estimating processes. Thus, the practical applications of BIM are vast and can be beneficial for companies.