04 March 2017
Last amended on
20 April 2021

As the world of construction develops, adapts to the BIM environment and embraces the challenges of becoming a digital industry, specification remains a critical part of the process. It is as essential now as it has ever been, forming an integral part of a building information model (BIM) and the digital golden thread of information that provides living, accurate and up-to-date data from asset design through operation and end of life. 

  • Capturing digital fingerprints
  • Recording decisions 
  • Encouraging transparency 
  • Creating accountability 
Specification: A detailed description of the dimensions, construction, workmanship, materials etc., of work done or to be done, prepared by an architect, engineer etc.

Shorter Oxford English Dictionary

What is specification? 

Let's look at what we mean when we talk about a specification; here is an official definition:

"Specification: A detailed description of the dimensions, construction, workmanship, materials etc., of work done or to be done, prepared by an architect, engineer etc."
- Shorter Oxford English Dictionary

A specification is the document that describes in words what cannot be visualised or explained on a drawing or model. This is not only applicable to construction; the same principles apply to all industries, from aerospace and oil and gas to automobiles and manufacturing. In construction, the specification can cover everything:

  • Site establishment.
  • Contract type.
  • Asset performance criteria.
  • Systems and product quality.
  • Applicable standards and how they are executed.
  • Specific products to be used. 

The type of specification can relate to the project or the procurement route – whether it is performance-based, prescriptive or proprietary – depending on project requirements.


  • Are required during the design stage. 
  • Form part of the contract documentation. 
  • Play a key role in project fulfilment. 
Early specification - lessons learned

15 reasons why specification is crucial to construction

Let’s look at some of the primary reasons why specification is essential to the construction process:

  1. The specification provides clear instructions on project intent, performance and construction.
  2. It can reference the quality and standards which should be applied.
  3. Materials and manufacturers’ products can be clearly defined.
  4. Installation, testing and handover requirements can be identified.
  5. Classification within the specification can be used to support handover and asset management. 
  6. It eliminates the need for information overload on the drawing or model, making identifying information easier. 
  7. A specification can support project costing, not only the materials and products but the performance and workmanship.
  8. Along with the drawings, the specification forms part of the contractual documents, helping minimise project risk and providing support should there be any legal disputes.
  9. It supports client brief interpretation and gives the client assurance that their commissioned asset is the one being delivered.
  10. It is essential for the construction phase and an important part of the soft-landing process, subsequent asset management and the lifecycle plan.
  11. By being clear, concise and information-rich, a specification provides answers to many onsite construction questions, saving the project team, client and contractor time and money.
  12. After project finish, office masters can incorporate best practices and lessons learnt, improving efficiency, providing quality assurance and ensuring project consistency. 
  13. Office masters also save the team time and money because they can be developed over time and adapted to suit a project's specifics, drawing on specialist knowledge when needed.
  14. The specification is a living document to be used by the complete project team throughout the construction phase; its value does not end at the design phase.
  15. Along with any variations or value engineering, it becomes a part of the project audit trail and a crucial part of the handover documents, forming the basis for asset management, asset maintenance, and even feeding into staff training and human resources policies.

When should you write a specification?

Specifications used to be one of the last items written before issuing a tender package; however this has changed over time, especially since the advent of BIM.

Nowadays, the best practice is to begin specification writing as early as possible in the project lifecycle. Early-stage specifications can capture information from the client review, documenting what the client is trying to achieve on the project. Early-stage work also provides a better understanding of a project's performance requirements. Any information incorporated into the client's EIR (employer information requirements) and discussions on complexes, entities, spaces, locations, elements, systems, and products contribute to the specification as it builds.

Specification and NBS

In essence, specification is about data communication and information exchange between client, designer and contractor. As project data requirements become more complex and we strive for more collaboration, it is crucial everyone has the same basis for project requirements – making specifications as essential now as they have ever been.

The team at NBS has been developing and delivering specification products and tools for over 40 years, and we are continuously reviewing our content to reflect industry changes. With cloud-based NBS Chorus, our users can write and deliver construction specifications in a BIM environment. For manufacturers, we have developed NBS Source. This building product library places manufacturer products directly in front of the people who matter as they are making product decisions. Finally, NBS users with a subscription to The Construction Information Service gain access to a comprehensive online collection of industry-relevant publications and can take advantage of embedded links within the specification guidance to access pertinent documentation.

This article is an update to Tina Pringle's article published in March 2017 and based on that year's NBS Specification Report.

Image: Franklin Hunting – 15 – fifteen on Flickr subject to a CC BY-ND 2.0 licence.

More about our products

Intelligent construction specification in the cloud

NBS Chorus is a flexible cloud-based specification platform that allows you to access your specifications across locations and organisations. It is suited to both performance and prescriptive specifying and has editable clauses that are supported by technical guidance. Our content is continuously reviewed to improve clarity and usefulness, informed by research, user feedback and industry drivers.

NBS Source

NBS Source brings together NBS BIM Library, NBS Plus and the RIBA Product Selector, providing a single source for product information that seamlessly integrates into a project's workflow and provides an additional level of enhanced product data in a consistent, structured format.

The Construction Information Service

CIS is a comprehensive online collection of industry-relevant publications from around 500 publishers. NBS users with a CIS subscription can take advantage of embedded links across specifications platforms to access research and reference documents. The content is fully searchable, intelligently classified and continuously updated. To learn more, visit https://www.thenbs.com/our-tools/construction-information-service.