- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 04 Mar 2021
Input specification vs output specification
Traditional specifications are ‘input specifications’. They are prescriptive, that is, they describe in detail the products, materials and work (the inputs) required by a contract. Typically, the development of the solution required by the contract is complete and no (or little) further development is required by the supplier. The specification is considered to be a ‘closed specification’.
Prescriptive input specifications give the client certainty about the end product when making investment decisions, but place a greater burden on them to ensure the product has been thoroughly considered, developed and described. They tend to be used where a very specific end result required.
Output specifications define only the outcomes (or outputs) that are required by the contract, that is, what it will enable the client to do. They are open specifications that do not attempt to address how those outputs might be achieved. For example, an output specification might require the provision of a space for teaching 30 primary pupils, but it would not specify the nature of the space, the types of doors and windows etc. The standard for what is required might be defined, for example, by reference to performance targets.
It is argued that output specifications can get the best value from the supply team by allowing them to adopt innovative solutions to the client's requirements and reduce whole-life costs rather than simply developing the client's pre-conceived solutions at the lowest price.
 Related articles on Designing Buildings Wiki
- Briefing documents.
- Feasibility studies.
- Final specifications.
- Insulation specification.
- Outline specification.
- Output specification
- Output-based specification.
- Performance specification.
- Prescriptive specification.
- Service level specification.
- Tender documentation.
- Tender process.
Featured articles and news
Different types of bridges are meant to move.
A logical approach to handling the internal voice of self doubt.
First fashionable in the US, decorative metal has become globally desirable.
Helping communities preserve and enhance historic environments.
Creating comfortable climates despite extreme temperatures.
Study examines how adjustable arrangements can succeed.
Government announces plans to improve accessibility.
Resource addresses pandemic-related NEC4 contract issues.
Incorporating EDI into the provision of fair access.
Government announces global innovation strategy.
An architectural biography. Book review.
The house where the future king of France lived.