Cost Implications of Architectural Design Variables

1
Cost Implications of Architectural Design
Variables
King Fahd University of Petroleum
Minerals Department of Construction Engineering
Management CEM 520 Construction Projects
Contracting Administration

• 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 (contd)

• 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 (contd)

• 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 (contd)

• 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

Technique Frequency Percent Cumulative Frequency Cumulative Percent
Prevailing Cost of Square Meter 3 30 3 30
Approximate Quantities Method 2 20 5 50
Database of Similar Projects 3 30 8 80
Unit Rate 2 20 10 100
10
(No Transcript)
11
DISCUSSION OF RESULTS (contd)

• 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 (contd)

• 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