Causes and Effects of Design Change in Building Construction Projects in Three Selected Southern Ethiopia Zones

-The main parties involved in Construction industry consists of Owner/Employer/client, Engineer/consultant, contractor, bank, insurance and government body. Among these one or more of the parties initiate the design change due to internal and external factors which lead to both time and cost overrun in construction project. The objective of this study is investigating the causes and effects of design change in building construction projects. The research methodology engaged a questionnaire survey containing of fifty-one (51) questions about the cause and effect of design changes during the building construction, which was distributed to the project managers, client and the Engineers. The questionnaire responses were analyzed based on Relative importance index. The results indicated that lack of design review during design process, errors and omission in design, plans change by client, incomplete contract documents, differing site conditions, lack of experience for design evaluation during design period and impediment in prompt decision making process were the most causes of design change. The results also showed that completion schedule delay, increase in project cost, wastage of materials during rework, productivity degradation and working extra hours (overtime) to meet deadlines of the project were the most impacts of design change


INTRODUCTION
The nature of construction industry is complex and uncertain because of different firms are involved from inception stage to commissioning stage. Design is a process of creating the description of a new facility, usually represented by detailed plans and specifications; construction planning is a process of identifying activities and resources required to make the design a physical reality [1] In an integrated system, the planning for both design and construction can proceed almost simultaneously, examining various alternatives which are desirable from both viewpoints and thus eliminating the necessity of extensive revisions under the guise of value engineering. Furthermore, the review of designs with regard to their constructability can be carried out as the project progresses from planning to design [1]. According to Ethiopia Construction industry the lion share of design preparation part goes to consultant firms. Design change is mainly common problem and it affects whole project construction performance according to the following literature reviews. The design change initiated by one the following parties owner, consultant, consultant construction management, politics and economics, natural environment, contractors, third party and advances in technology [2]. Design changes requested by owners include additions, deletions and/or modifications to the original scope of the work [3]. According to first Ethiopia condition of contract (BATCODA) the Consultant shall prepare as built final drawings and records of the works to give information of both visible and concealed work to enable the Investor carry out future changes in design or modification of works with ease and without measurement and investigation. are complete and considers important sub-processes such as standardization, value engineering, and reviews [5]. But the factors depend according to the research area. The research conducted in Tanzania investigated that the client's factors and design consultant factors have more influence in change of design during construction stage for internal factors and the environmental factors found to have large influence to change of design followed by the third parties factors for external factors [6]. According to [7] the most five common causes of change orders can be identified as: change of plans by owner, change of project scope by owner (additionalenhancement), problems on site, errors and omission in design (main element), poor design and poor working drawing details (secondary element). Another research study found that the owner was the main factor that caused design changes in a construction project and other factors were respectively design consultants, construction management consultants, political and economic matters, the natural environment, contractors, third parties and the advance of technologies [2]. The critical appraisal of literature relating to causes of design changes and the resultant rework that cause delay and disruption which result in time delays and cost overruns in building construction projects has been presented. This study establishes that literature linking design changes and rework in construction projects is limited but found out that design changes is the significant factor for time delays and cost overruns [8]. According to literature review [9] the major ranked causes of design change as change of plan by owner, Substitution of materials, change in design by consultant; Errors and omissions in design, the scope of work for a contractor is not well defined, Conflict between contract documents, differing site conditions, change of plan by client; The lack of coordination between contractor and consultant; The contractor's financial difficulties, owner's financial problems, Workmanship or material is not meeting the specification, Contractor's desire to improve his financial situation; The required labor skills are not available, The required equipment and tools are not available, New government regulations, and Weather conditions. A study conducted in Oman investigated and listed causes of change in public construction project as Owner instructs additional work; Owner instructs modification to design; Nonavailability of construction manuals and procedures for project construction in Oman; Non-availability of engineering licensing for engineers in Oman to maintain the quality of consultancy services; Poor communication between relevant governmental units and the owner; Nonavailability of overall project planning; Unrealistic design periods; Unrealistic construction schedule; Owner fails to make decisions or review documents at the right time; Low consultancy fee or less experienced designers; Nonavailability of records of similar projects in Oman; Failure by the consultant to provide adequate and clear information in the tender documents; Natural growth of the project was not anticipated at the design stage; Owner's needs during the design stage are unclear or not well-defined; The contractor uses the gray areas in general conditions and request variations to the contract; Design errors; The design and construction criteria are outdated and do not suit the present construction technology; The contractor misses variations instructions; Non-availability of qualified engineers from the owner side; Consultant not familiar with the regulations and construction permits in Oman; Unilateral decisions made by the owner without proper considerations to the contract; Consultant's supervisors do not have collective experience about construction projects in Oman; Failure by the consultant to perform design and supervision effectively; and Poor project management by contractor [10]. The study in Pakistan indicated top three discrepancies between design and construction as provision of incomplete data to designers, lack of interest by approving authorities to carefully check the design, and ownerproposed changes due to financial problems [11].
Generally Causes of design change as described by different authors summarized as client related (change requirement, new technology, value Engineering, unclear brief), contractor related (request to use available material, alternative construction methodology), site related (location, underground condition) and design related (design error, inconsistent site condition, design omission, unpredictable circumstance during construction, modification to design).

EFFECT OF DESIGN CHANGE IN BUILDING PROJECT DURING CONSTRUCTION
The construction industry performance measured by three major parameters cost, time and quality. However, the design change affects the whole process of project and the effects listed below are mostly occurred in Ethiopia Construction industry. Cost overrun, time overrun, quality problem, increases overhead expenses, wastage of materials due to rework, Productivity degradation due to equipment and material, claim and disputes occur between client and contractor. The most common effects for those projects that change of design took place during construction stage were delay of the projects, increasing of cost of the project (cost overrun), abandoning of the project, wastage of materials and conflicts between the parties [6]. The study conducted in Nigeria found that design change due to poor working drawing (omission on structural drawing) leads to variation [12]. Design changes frequently impact project cost and time and have the potential to increase the possibility of conflicts between owners and contractors. Project time and cost change impact can become severe if owners do not consider the fact that a change in one part of the project may cause a series of changes in other parts of the project, which is known as the "change ripple effect." Therefore, for the wellorganized delivery of construction projects, it is essential to have an efficient design change management system [3]. The critical appraisal of literature relating to causes of design changes and the resultant rework that cause delay and disruption which result in time delays and cost overruns in building construction projects has been presented [8].
The effects of design change from different scholars can be summarized as additional payment for contractors, rework, demolition, completion schedule delay, increased overhead expenses and increase the possibility of conflicts between owners and contractors

RESEARCH OBJECTIVES
The objective of this study is to identify Causes and effects of design change in building construction projects of three selected southern Ethiopian zones.

METHODOLOGY
In order to Determine and analyse the causes and effects of design change in public construction projects of Wolaita Sodo, Arba Minch and Hawassa cities, a wide range of personnel involved in construction projects of southern Ethiopia cities were targeted. Personnel were selected from project managers, consultants, contractors, client's representatives and construction managers. A questionnaire was carefully designed from previous preliminary investigations conducted in construction projects. It was organised in the form of a priority scaling (1=very low, 2=low, 3=medium, 4=high, and 5=very high). The questionnaire was distributed to purposively selected sample of clients, consultants and contractors. The sample selected for each of the three groups is described below as:  Clients encompassing the government agency responsible for the projects, private organisations, and individual owners.  Consulting groups who designed the projects of southern Ethiopia.
 Contractors who are executing in the construction projects of southern Ethiopia. Respondents were from public and private agencies that sponsor construction projects, and the contracting and consulting organisations that work for them.

Data Analysis
The Relative Important Index (RII) method was adopted for similar studies to determine the relative importance of various factors [13]. This method is applied to this study to identify the Relative importance of various causes and effects of design change based on responses from contractors, owners and consultants.

RII=(
where: W = the weight given to each factor by the respondents A = the highest weight = 5 N = the total number of respondents. The RII is used to rank the groups of questionnaire by calculating the average of relative importance index of all factors in the group.  From the table 1 and figure 1 above lack of design review during design process with RII=79% takes the first place as a cause of design change at the study area. Design review is the process of evaluating the design against its requirement to identify issues before proceeding the work. It should be a culture & mandatory for every design. Lack of design review results change of design after the project is started. Errors and omissions in design with RII=77% is the second cause of design change in construction projects as respondent's perspective. Design error is lack of instruction in the specification and or plan and design omission is missing what is compulsory to complete the design or comply with the design code. Once again, this result change in design and costs the owner for its replacement. The way to reduce change of design caused by errors and omissions is using design templates. Change of plan by clients with RII=65% is the third cause of design change. This is due to insufficient time allocation for briefing, absence of end user's involvement, late exposition of requirements, and inexperience of client in construction [14]. The fourth and fifth cause of design change is incomplete contract document with RII=58% and Differing site condition with RII=56% respectively.  [15]. Increase in project cost with RII=88% is the second impact of design change. Design change at the stage of construction requires replacement of design (re design) and or rework. Once again this costs the client which results increase in project cost as a whole. Wastage of materials during rework with RII=81% takes the third place as effect of design change. Design change at the construction stage may require demolition and rework of already constructed part. This results wastage of construction material. Productivity degradation with RII=75% and working extra hours (overtime) to meet deadlines of the project with RII=68% is the fourth and fifth impact of design change respectively.

CONCLUSION
The finding from the study and literatures revels that the causes of design change in the study area includes (1) Lack of design review during design process, (2)Errors and omission in design, (3)Change of plan by clients,