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STEEL CONSTRUCTION COSTS IN EARLY PROJECT PHASES, GERMANY VS. FRANCE
Christopher Hagmann University of Stuttgart
Christian Stoy University of Stuttgart
Construction costs are relevant success factors of building construction projects and most efficiently defined in early project phases. Thereby, reliable sources of cost indicators are required when analysing economic alternatives. With rising steel prices, the steel producing company ArcelorMittal together with UNTEC (French National Union of Construction Economists and Coordinators) developed a steel construction cost information and performance database for French planning institutions. After years, a similar product is about to be introduced to the German market in cooperation with CEEC (European Council of Construction Economists). As both countries work with different standards, however research on the German steel construction data was required to develop a similar database for the German market. In this field research, feedback from 100 institutions and companies (grouped into framework, floor, roofing, façade etc.) is statistically analysed and the results compared with the French data. This is the first study in a series to be carried out in the next few years around Europe.
KEYWORDS: steel, construction costs, early project phases, Germany.
INTRODUCTION
Cost planning is one of the main tasks for most participants involved in building construction projects today, as qualities, schedules and costs are relevant success factors. Compiling cost identifications in early project phases (budget and preliminary estimate) poses an considerable challenge onto architects, engineers and the awarding authority, as the base of information still is rather small at this time, although cost identifications are requested of a very precise quality (Ruf, 2003). Usually this first stage of cost planning is an early cost projection, based on single factor calculations using cost indicators (Stoy et al., 2008).
In this process, the qualities of both quantity determination (reference unit) and chosen cost indicator have the same importance for the final result, as normally the following type of equation is applied for cost identification:
Cost Indicator x Reference Unit = Cost Forecast (equation 1)
In the case of France and Germany, the exact determination of a project´s quantities is based on national standards that contain similarities, but also important differences in detail (Hagmann et al., 2008). These differences have a possible impact on both the development of cost indicators and their application in calculations of cost identification.
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Furthermore, the contents of a cost indicator are related to material, labour time and specific coefficients. And these components again are partly based on national standards. In summary, a cost indicator may be based on a quite complex construction, always driven by different national standards.
For this reason decision was taken to realize the publication for the German market not by using the French cost indicators as they were. And not even by trying to localize them using a (to be found) French-German steel construction cost translation factor. But the approach agreed by all involved in the project was to carry out a survey on steel construction cost indicators in Germany, based on the French framework.
This paper describes the approach of the survey and the validation process, to end with the presentation of some exemplary German steel construction cost indicators compared to their French equivalents.
FRENCH BACKGROUND
In France, institutions have already elaborated and published a special data base for cost indicators of steel constructions some years ago (Les Carnets de l´acier, 2006). This tool enables to quickly estimate the construction cost of a building or part of the work, considering not a specific product but functions like structure, envelope, equipment, surface treatment or fire protection. The approach by function takes into account the type of building or system with weighted averages (in Parisian area) calculated and validated for areas from 300 to 1000 m². Based on enterprises´ bids analysis, these values integrate the different components, in order to obtain an estimation of the costs, which are directly and simply exploitable to get a spread of cost indicators. For example, the function "Façade" is composed of primary framework, accessories, insulation, aspects of the surface; including both material and labour costs.
After several years of successful experience in France, decision was made to prepare the introduction of a similar document on the German market. One of the main questions at that time was, whether the French data base could be translated into the neighbouring country for instance by simply adding a certain French-German coefficient to every existing French cost indicator. To get an answer to this question, the European Council of Construction Economists (CEEC) was asked to join and supervise the project by adding its international experience. And the final agreement of was to carry out a survey on the German market.
SURVEY
The field research by questionnaires was conducted to collect cost indicators for steel construction works and elements in Germany from the German planning und building industry. A total of over 600 of questionnaires has been sent to over 300 contacts, followed by uncounted phone calls. The collection of data was carried out from November 2007 to February 2008. In order to receive comparable prices, eight different questionnaires had been established to cover the different steel construction topics. Each of them asking for cost indicators valid for functions of the following type of building, inclusive supply (material) and laying (labour). All items are entirely based on German standards, mainly on DIN 276 (DIN 2006) and DIN 277 (DIN, 2005).
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General specifications of our case study building as indicated on every questionnaire:
• Gross external floor area: 800 m² to 1400 m² BGF • Snowload-zone: II • Windload-zone: III • Groundlevel: max. 500 m above sea level • Compact building geometry
Further specifications are defined for every of the different topics of the questionnaires:
(1) Framework: the framework weights and prices including columns, connections and simple bracings or stiffings; the mixed construction takes into account the collaborating action studs shear connectors, but no slabs (see: (2) Floors).
(2) Floors: the indicated prices include complete placing with additional formwork, temporary propping, additional reinforcement and pouring of concrete; the prices include the data for fire resistance F90; a deduction in % is indicated for F30 construction.
(3) Fireprotection: massivity factor of about 140-180 which corresponds to the profile range of IPE 300 to 450 and the whole HEB range for example.
(4) Façade: secondary frameworks are included only if necessary; finish of elements in pale colours (class 1); no openings included; spans of 7.5 m.
(5) Roofing: are included if necessary; finish of elements in pale colours (class 1), no openings included; spans of 7.5 m.
(6) Doors & Windows: cost indicator takes no account of surface treatment (paint, galvanization, thermal lacquering); normal dimensions of glazing surfaces per element (1 m x 2 m for doors and 1 m x 1 m for windows); prices without specific metal fittings like door closer etc.; no special acoustic performance; fanlight excluded, specific ironmongery excluded.
(7) Metalworks: all stairs are standard with railing and handrails.
(8) Anticorrosion: the indicated prices include transportation up to an average distance from and to the workshop; costing modes are different from one industrialist to another, so in order to simplify, the mode "empty for full" in m² is asked.
VALIDATION
Despite the large number of questionnaires sent out and uncountable personal interviews, we received only about 100 with filled out cost indicators, that were all put in a data base.
In a first validation step, the data base provided a statistical overview of the survey results: lowest and highest value (and the fork between them), lower and upper quartile, median and average value (see Table 1). Finally, this method indicates outliers that you might want to discuss with its provider to avoid misunderstanding of item definitions.
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In a second step, the upper and lower quartile was chosen in most cases to build the upper and lower value, as we agreed not to publish the cost indicator of an item as a single value only, but as a range (see Table 1).
Table 1: Validation step 1 and 2: descriptive statistics (extract from chapter: framework)
In a third step, the already published French data was integrated into the data base and each French item allocated to its German equivalent. As the latest French data available dated from December 2005, these cost indicators had to be updated by an index (in case of framework: 12%) provided by UNTEC, in order to be comparable to the German data, valid for the 1st quarter of 2008.
Whenever possible the data published by BKI (BKI, 2008) was used as an additional validation step to see the variation between the survey results based on a theoretical case study and the BKI data based on executed real life projects (see Table 2). Unfortunately, BKI has a large data base for many other areas than steel construction.
In case of particular variations between the German and the French indications, the data of this specific item was analysed into material costs, labour time and their coefficients, in order to understand where the difference comes from.
Every item was declared “validated as pre-result” only if both the French and the German side agreed to.
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Table 2: Validation step 3: comparison to French data and BKI (continuation from Table 1)
As the last step of validation, these pre-results were presented to all CEEC delegates and some chosen construction cost estimation professionals in Germany to get their comments on usability and quality of the cost indicators. And after their final agreement, nearly 300 items were “validated to be published”.
RESULTS
The following three figures are comparing the results of the German survey after validation with the French data in the three exemplary chapters: façade (see Figure 1), framework (see Figure 2) and fire protection (see Figure 3).
To some extend, Figure 1 (façade) gives the impression that the consideration at the very beginning of this project, the idea of a French-German coefficient, seems to be quite likely.
But even if Figure 2 (framework) might nearly work with a coefficient, it would have to be a different, as the results comparing both countries are inverted.
And Figure 3 (fire protection) gives an example of a chapter, where the tendency is changing from one item to another.
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Figure 1: Comparison of results (extract of: façade)
Figure 2: Comparison of results (extract of: framework)
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Figure 3: Comparison of results (extract of: fire protection)
CONCLUSIONS
This paper describes a survey carried out on steel construction cost indicators in Germany, based on a similar project in France. The results of the present study show clearly, that it is not possible to use a single French-German coefficient for simple mathematical translation of steel construction cost indicators at the level of single items from France to Germany.
One of the reasons is the fact of different standards used in both countries for quantity determination. Further research may show, to what extend the possible introduction of an European Code of Measurement for Cost Planning could solve this problem. On the other hand, the impact of different market situation as well as different construction habits (technical solutions applied) still remains to be analysed.
This could be useful for example when the existing steel construction cost data bases will be translated to even more European countries within the next years.
ACKNOWLEDGEMENTS
This research was supported by ArcelorMittal Building & Construction Support. We thank our colleagues from CEEC, RICS, UNTEC, ArcelorMittal and from Société ECO.METAL who provided insight and expertise that greatly assisted the research.
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REFERENCES
ArcelorMittal (Ed.) (2008) Kosten im Stahlbau, Basisinformationen Deutschland 2008. Luxembourg: ArcelorMittal. Available as PDF at: http://www.constructalia.de .
BKI Baukosteninformationszentrum Deutscher Architektenkammern (2008) BKI Baukosten 2008, Teil 3: Statistische Kostenkennwerte für Positionen. Stuttgart: BKI.
DIN Deutsches Institut für Normung e. V. (2005) DIN 277-1 Grundflächen und Rauminhalte von Bauwerken im Hochbau – Teil 1: Begriffe, Ermittlungsgrundlagen. Berlin: Beuth Verlag.
DIN Deutsches Institut für Normung e. V. (2005) DIN 277-2 Grundflächen und Rauminhalte von Bauwerken im Hochbau – Teil 2: Gliederung der Netto-Grundfläche. Berlin: Beuth Verlag.
DIN Deutsches Institut für Normung e. V. (2005) DIN 277-3 Grundflächen und Rauminhalte von Bauwerken im Hochbau – Teil 3: Mengen und Bezugseinheiten. Berlin: Beuth Verlag.
DIN Deutsches Institut für Normung e. V. (2006) DIN 276-1 Kosten im Bauwesen – Teil 1: Hochbau. Berlin: Beuth Verlag.
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