An Application of life cycle costing technique to the construction industry in Kenya with particular reference to roof covering materials. A case study of Nairobi

Abstract

There is evidence that large numbers of buildings do not achieve the level of performance intended by designers and the client. In many cases short- comings appear as defects of either design . materials or workmanship or a combination of these proportions the relative of which are difficult to determine . Some instances are spectacular and involve lar ge expenditures on remedial wor k or in the very extreme cases the demolition of recently comple t ed buildings . Amongst the building element s with greatest short- comings are the roofs . Roofs are the most exposed to the severe environment and apparently contribute between 12~ and 16% of the total initial cost of construction. Any designer dealing with buildings would be failing in his function as an adviser if he did not understand the problems involved in maintenance and running costs of buildings and apply this knowledge at the design stage. The u ser costs plus the initial costs constitute the total building costs . The initia1cos t s are those which arise directly out of the erection of the building and management of its contract, and cost of construction itself, including the cost of raising capital and any other expenditure necessary to change the state of having an empty site to one of having a site with a building on. Comparatively capital cost is often the major component for decision making. Many organizations concentrate on this to the exclusion of most other facets, prefering to consider asset lives in terms of capital cost related to profitability and payback. Yet it may be the smallest component of cost . For many purposes this results into many inadequate decisions regarding productive assets, but it may well mean the purchase of an asset with a worse performance over its whole life. On t he other hand are, user costs, which include maintenancerepairs, redecoration, operating costs such as routine cleaning and care-taking and in addition such alterations, adaptions, or conversions as may be necessary and the payment of rates and insurances. The essential of costs-in-use is to provide a rationale for choice in circumstances where these alternatives differ not only in their initial costs but also in their subsequent running costs . The use of lifecycle costs enables the various technical and operations options to be compared and trade offs measured in common terms. The need for the study arose because there is little known about the influence of design on subsequent costs of maintaining buildings. This gap of knowledge means that designers have failed in their duties, for they cannot provide appropriate life cycle costs of the alternative design of roof components with a view to minimizing the total costs of the component . The role of life cycle costing is to design out maintenance, which is obviously a matter of comnromise, since neither the designer nor the manufacturer will be influenced by solely maintenance considerations when planning and producing new building roofing components or materials. The study hopes to create an awareness within both the public and private sectors in the industry for the use of life cycle costing technique in order to minimize total costs of buildings or their components. The literature reviewed include the construction process in the construction industry outlining all thP variou~ stages right from inception to the completion of the project including maintenance defects and liability period. The concept of total building costs, components of life cycle costing, life spans of the various (v) roof covering materials are discussed in the literature review section . Chapter three reviews the various cost models and life cycle cost methodologies with a view to identifying a suitable cost model for use in this study . ln this section cost models are discussed, and a cost model has been modified, and i~entified as suitable and used in this study . Chapter four deals with building design and construction in Nairobi laying special emphasis on the influence of climate on design, and the effects of weathering on the various roof covering materials. Chapter five deals with data analysis and discussion on the data . It is shown that asphalt has shorter life span in the study area than the expected lifespan . Roofing felts and asbestos are not significantly affected by change of climatic conditions at 95% confidence level. Galvanized corrugated iron sheets have a longer lifespan in the study area than their expected lifespans according to the results, and finally mangalore tiles show a singificantly shorter lifespans in the study area than in their expected lifespans as identified in the literature review . The study shows that the total life cycle costs of the various components differ significantly, and therefore caution should be taken when choosing design alternatives . These have been tested bearing in mind the sensitivity analysis of discount rates at both 3% and 6~ respectively, as explained in the text of this thesis. lt is recommended that data banks be established by every department or body that deals with the construction of buildings at various towns, municipalities and cities in Kenya . It is worth recommending that more work be carried out in other towns and especially Mombasa Municipality where climatic conditions are more (vi) severe than in Nairobi which possibly would change some of the findings of t his s t udy . The study has mainly explored the importance of life cycle costing for roof covering materials, thus laying a basis for future researches on the other building elements