EVALUATION OF EFFECTS OF CHANGES IN BUILDING DESIGN ON TOTAL COST OF BUILDING PROJECTS

EVALUATION OF EFFECTS OF CHANGES IN BUILDING DESIGN ON TOTAL COST OF BUILDING PROJECTS

ABSTRACT

The contribution of the construction industry to national economic growth necessitates improved efficiency in the industry by means of cost-effectiveness and timelines and would certainly contribute to cost savings for the country as a whole. Since cost has been identified as one of the measures of function and performance of a building, it should be capable of being “modelled” in order that a design can be evaluated. It is essential that Architects should be fully aware of the cost consequences resulting from changes in shape, size, storey height, total heights and other building charateristics. It is particularly worrisome that there has not been sufficient research that provides clear indications of the degree to which changes in the parameters of the building( design variables) will affect its cost, while providing the same accommodation and quality of specification. The cost effect of storey height was examined with the illustration two storey building and four storey building which was tagged design A and B and also a priced bill of quantities (BOQs) were prepared according to the standard method of measurement of building works. And the comparison were made based on elemental cost of the building of the same plan. Also this designs are further analyzed based on regression and rank correlation analysis. The findings revealed that design “A” is more economical because from the analysis, it was discovered  that “A”  is N69,910.16 cost per m2 gross floor area, and has 100% savings,  while design “B” is N77,491.55 cost per m2 gross floor area with increase 110.84% increase.  This means  that design “A” is more economical to erect, due to the fact that design “B” has an increase of 10.84%. The study concluded that high-rise building involve risk of life during the construction of roof and other services installation which makes more expensive to construct. The study recommend that the client should be fully involve  the services of quantity surveyors and other professionals during the design stage in order give advice on cost control and cost implication of the design variables during the design stage

CHAPTER ONE: INTRODUCTION

1.0       BACKGROUND OF STUDY

The construction industry is the largest and most challenging industry in the world. The Nigerian construction industry continues to occupy an important position in the nation’s economy. The contribution of the construction industry to national economic growth necessitates improved efficiency in the industry by means of cost-effectiveness, timelines and would certainly contribute to cost savings for the country as a whole.

The processes in construction projects can be divided into three phases; Project conception, Project design, and Project construction. Project conception entails the recognition of a need that can be satisfied by a physical structure.  The project design phase translates the primary concept into an expression of a spatial form that will satisfy the client’s requirements in an optimum economic manner. The construction phase creates the physical form that satisfies the conception and permits the realization of the design. The services of Construction firms and contracting organizations are often engaged to assist prospective building owners in the realization of a construction facility.

According to Frederick and Jonathan(2001), Building design is a process of providing all information necessary for construction of a building that will meet its owner s requirements, serve purpose specified by client and also satisfy public health, welfare and safety requirements. In the recent times, people have needed some idea of what a new building would cost before they start work on it. For reasons stated by Mbachu and Olaoye (1999) as having the right building at the right time, and at the right cost, which are the expectations of any building owner.

Presently, due to the prevailing economic condition which has made the availability of capital for construction difficult there is greater awareness of cost and thus made it essential to ensure that whatever amount is available is judiciously utilised to secure best economic advantage.

Since cost has been identified as one of the measures of function and performance of a building, it should be capable of being “modelled” in order that a design can be evaluated. This will assist in providing greater understanding and possibility of predicting the cost effect of changing the design variables on cost. Cost modelling has been defined by Ferry and Brandon(1991) as the symbolic representation of a system in terms of the factors, which influence its cost.

Seeley(1993) stated that the cost of buildings is influenced by a variety of factors, some of which are inter-related. It is essential that builders who are the project manager should be fully aware of the cost consequences resulting from changes in shape, size, storey heights, total heights and other building characteristics.

1.1       THE NEED FOR THE STUDY

The Construction Industry Research and Information Association(CIRIA) program of research identified a constraint for achieving good construction by stating that “the achievement of good construction depends on both designers and cost estimators being able to see the whole construction process through each other’s eyes”.

The principal components of the cost of any construction facility include site, location and accessibility; soil and subsurface conditions; time and season; climatic conditions; wage agreements; strikes and lockouts; market prices of basic materials; availability of money; demand for construction; political and economic climates; and design style. While several of these factors could be constant for a given project, the design style could be varied in order to select the most economical option (Ibrahim, 2003).

It is in fact customary that for any one project, the designer will, in liaison with the client, consider several different options as possible economical design solution.  The factors that have economic consequences in the various design options are identified and examined, and this often form the basis of selecting the most suitable and appropriate proposal for the prospective client to embark upon.

1.2       STATEMENT OF THE RESEARCH PROBLEM

It is particularly worrisome that there has not been sufficient research that provides clear indications of the degree to which changes in the parameters of the building (design variables) will affect its cost, while providing the same accommodation and quality of specification.

Most building projects remain uncompleted because of the financial problems encountered by clientsas a result of the client ordering changes to the initial design without recourse to the impact on the cost or estimating the possible costs and match it to the actual budget (Ibrahim, 2003).

1.3       AIM AND OBJECTIVES

1.3.1    The aim of the study is to show how buildingdesign  affect the total construction cost of a residential building.

 1.3.2    The principal objectives of this study are to:

1. To determine the relationship between the total cost of buildings and the building design
2. To examine the effect of building design on the construction cost of a residential building.
3. To outline ways of minimising the effects of the building design on the cost of the building construction.

1.4       METHODOLOGY OF THE RESEARCH

1.4.1       DATA COLLECTION

For the purpose of this research, the researcher shall use primary data retrieved using structured questionnaire and personal interview. The closed ended structured questionnaires will be distributed using stratified random sampling method. The population will be divided into class of firm (small, medium and large scale). Further criteria for selection of firm to be interviewed includes the type of construction work undertaken by the firm, the size of the firm, the type of ownership of the firm, the complexity of project handled by the firm etc.

1.4.2    ANALYSIS

Table, relative index scale, shall be used for data presentation. SPSS charts and excel was used to analyze the presented data.

1.5       SCOPE AND LIMITATION OF THE STUDY

This research considered the effects of building design such as perimeter, floor area and height of buildings on the cost of elements of some completed residential buildings in the federal capital territory Abuja.

The following restrictions will be imposed on this study because of time and cost constraints:

1. The design variables to be considered were limited to those that are Architectural in nature, detail implications of structural, mechanical and electrical engineering services
2. The statistical sample of respondents selected to participate in the questionnaire survey was restricted to firms in Abuja only. The questionnaire will be administered to the entire population using stratified random sampling method.
3. The structure of the questionnaire inquiry focused on cost estimation provided at the early stages of residential building projects. The choice of residential buildings is because they are the commonest and the most demanded form of construction due to their strategic importance to the social and political status of human race.
4. The empirical analysis was restricted to considerations related to residential building designs.
5. Only the effects of changing the design variables were measured in the empirical studies. The variables of interest in this study include Plan shape, Building average storey height, Number of floors, Circulation space and Glazed area.  All the other cost factors were held constant during the simulations.

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