1. Cost Implications of Architectural Design Variables Ahmed S. Al Zahrani December 2005 King Fahd University of Petroleum & Minerals Department of Construction Engineering & Management CEM 520 Construction Projects Contracting & Administration

2. OUTLINE  INTRODUCTION  LITERATURE REVIEW  RESEARCH METHODOLOGY  RESULTS  CONCLUSION & RECOMMENDATIONS

3. INTRODUCTION  Background  Early cost estimates  Different cost estimation techniques  Many factors affecting the estimation  Objectives  Investigate cost estimation techniques used in Eastern Province for residential buildings.  Investigate procedure in accounting for design variables in the estimation.  Study the effect of design variables on the construction cost.

4. INTRODUCTION (cont’d)  Significance of Study  Establish scope & methodology of cost estimation for the benefit of entire construction industry.  Indicate the accuracy level in order to improve the current techniques.  Assist the designers in understanding the cost implications of design variable.  Scope & Limitations  Eastern Province  Residential building business only  Design variables that architectural in nature.

5. LITERATURE REVIEW  Estimation Techniques  Accuracy depends on skills of the estimators  Each estimates contains: quality, quantity, & cost  Main Techniques:  Order-of-Magnitude Estimate: (min info needed)  Functional Unit Method  Floor Area Unit Method  Building Volume Unit Estimates, etc.  Budget Estimates  Requires a large extent of information  Accurate  Better for project feasibility

6. LITERATURE REVIEW (cont’d)  Design Variables  Design variable: the parameter or unit of a building design that can be kept constant in one case, but which may be varied in different case.  Major design variables: Building Plan Shape Size of Building Average Storey Height Number of Storeys Building Envelope Circulation Space Grouping of Buildings Mech./Elect. Services Column Spacing Floor Spans Floor Loadings Constructability

7. RESEARCH METHODOLOGY  Phase I: Literature Review  Find out the main cost estimation.  Find out the main design variables.  Phase II: Survey of A/E Firms  Questionnaire distributed to 140 registered firms.  Only 30 firms satisfy the scope of the study.  19 firms responded to the questionnaire.  Questionnaire includes (48 questions):  Firm General Information (21)  Estimating techniques, factors influencing the choice of a technique, & procedures for accounting for the variables (27)

8. RESEARCH METHODOLOGY (cont’d)  Phase III: Simulation for Design Variables Preparation of Cost Estimate Changing of Design Variables Analysis of Changes Observed

9. DISCUSSION OF RESULTS  Early Cost Estimates & Design Variables:  only 10 firms (53%) prepare early cost estimate.  Summary of Estimating Techniques: TechniqueFrequencyPercent Cumulative Frequency Cumulative Percent Prevailing Cost of Square Meter 3303 Approximate Quantities Method 220550 Database of Similar Projects 330880 Unit Rate22010100

11. DISCUSSION OF RESULTS (cont’d)  Empirical Analysis of Design Variables: Introduction Hypothesis Statement Analysis Conclusion

12. CONCLUSION & RECOMMENDATIONS  Conclusion  53% only do early cost estimates.  Project size was the most important factor that impacts the method selection followed by the information available.  Most important factors which impact the decision on design variables are:  shape of plot plan  land cost for total number of storeys  intended average storey height  circulation space  percentage of glazed area of building services.  The simpler the plan shape, the lower is the cost.  The cost per square meter increases with the average storey height of a building.

13. CONCLUSION & RECOMMENDATIONS (cont’d)  Recommendations  Specialized cost estimating packages to enhance accuracy.  Increased demand for early cost estimating for the clients to enhance good planning.  Innovative practices to be encouraged by A/E firms in order to avert the consequences of over-assessment & under- assessment of cost estimates.  A/E firms to adopt the relationships between the design variables and cost.