Cost Implications of Architectural Design Variables

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

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:

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:

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.

14. THANK YOU