If the initial construction costs of a building is 1, then its maintenance and operating costs over the years is 5, and the business operating costs (salary of people working in that building) is 200.
The rule originated in a Royal Academy of Engineering paper by Evans et al.
Sometimes the ratios are given as 1:10:200. The figures are averages and broad generalizations, since construction costs will vary with land costs, building type, and location, and staffing costs will vary with business sector and local economy. The RAE paper started a number of arguments about the basis for the figures: whether they were credible: whether they should be discounted; what is included in each category. These arguments overshadow the principal message of the paper that concentration on first capital cost is not optimising use value: support to the occupier and containment of operating-cost. Study by the Constructing Excellence Be Valuable Task Group, chaired by Richard Saxon, came to the view that there is merit in knowing more about key cost ratios as benchmarks and that we can expect wide variation between building types and even individual examples of the same type.
Hughes et al, of the University of Reading School of Construction Management and Engineering, observed that the "Evans ratio" is merely a passing remark in the paper's introduction (talking of "commercial office buildings" and stating that "similar ratios might well apply in other types of building") forming part of a pitch that the proportion of a company's expenditure on a building that is spent directly on the building itself (rather than upon staffing it) is around 3%, and that no data are given to support the ratio and no defence of it is given in the remainder of the paper. In attempting to determine this ratio afresh, from published data on real buildings, they found it impossible to reproduce the 1:5:200 ratio, in part because the data and methodology employed by Evans et al. were not published and in part because the definitions employed in the original paper could not be applied. The ratios that they determined were different by an order of magnitude from the 1:5:200 ratio, being approximately 1:0.4:12. They observed that "everyone else who deals with real numbers" pitches the percentage somewhere between 10% and 30%, and that their data support 12%.
They note (as does Clements-Croome) that the three costs for every individual building are affected by a plethora of factors, yielding a wide variation in ratios. They suggest that "[p]erhaps the original 1:5:200 ratio was simply meant to be a statement to focus clients' attention" on the importance of considering the higher staffing costs of a building relative to its operating and construction costs, and to encourage people to not be too concerned with higher initial build costs to improve build quality and reduce later lifetime costs. They state that if this is so "then subsequent users of the ratio have misused it", and that the frequency of use of the ratio is not problematic, but that the authority and gravitas that are assigned to it is. They conclude that "perhaps the most worrying feature of this whole discussion is how this passing introductory remark in the paper by Evans et al has gained the status of a finding from research carried out by the Royal Academy of Engineering, which it most certainly is not!".
- Evans, R., Haryott, R., Haste, N. and Jones, A. (1998) The Long Term Costs of Owning and Using Buildings, London, Royal Academy of Engineering.
- Evans, Raymond; Haryott, Richard; Haste, Norman; Jones, Alan (2004). "The long-term costs of owning and using buildings". In Sebastian Macmillan (ed.). Designing Better Buildings: Quality and Value in the Built Environment. Taylor & Francis. pp. 42–50. ISBN 0-415-31525-5.
- Tunstall, Gavin (2006). Managing the Building Design Process. Elsevier. p. 113. ISBN 0-7506-6791-5.
- Clements-Croome, Derek (2004). Intelligent Buildings: Design, Management And Operation. Thomas Telford. p. 342. ISBN 0-7277-3266-8.
- Saxon, Richard (2005) Be Valuable: A guide to creating value in the built environment, London, Constructing Excellence
- Hughes, W.P.; Ancell, D; Gruneberg, S; Hirst, L (2004). "Exposing the myth of the 1:5:200 ratio relating initial cost, maintenance and staffing costs of office buildings". Proceedings of the 20th Annual ARCOM Conference. Heriot-Watt University: 373–381. Retrieved 7 November 2013.