Cost estimate tolerances
The specifications of the General Services Administration (GSA) and the American Institute of Architects (AIA) indicate, depending on the project stage, the acceptable tolerances in a project cost estimate, as summarised in the following table:
| Project phase | Tolerance (%) according to GSA | Tolerance (%) according to AIA |
|---|---|---|
| Previous studies | 10 | 10–15 |
| Preliminary draft | 7–10 | 7.5–12.5 |
| Basic design | 5–7.5 | 5–10 |
Depending on the level of detail and development of the project (preliminary analysis, draft project and design project), the calculation of the bill of quantities is adjusted accordingly, thereby increasing its level of accuracy.
In the case of CYPE Cost Estimator, the tolerances relating to the deviation of the initial bill of quantities from the final cost of the works, provided that the initial project parameters regarding areas, heights or construction characteristics are maintained, are summarised in the following table:
| Project phase | Tolerance (%) CYPE Cost Estimator |
|---|---|
| Preliminary analysis | ≤ 12 |
| Draft project | ≤ 10 |
| Design project | ≤ 7 |
