05 October 2021
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Specifications for architecture, engineering, landscape, and the built environment give construction teams a detailed overview of the project work, required performance, and product selections. This article answers some commonly asked questions about specification and NBS.

1. What is a specification?

Specification is the skill of recording specific requirements about work you (or your client) want to be carried out. A construction specification is a well-structured, detailed description of the quality, standards, workmanship, materials, and completion of work to be done which evolves across a project. Specifications are often prepared by architects, engineers, and designers referred to as specifiers, and may be published as part of the contractual documentation for contractors to be read in parallel with models and drawings, and as part of the handover information.

2. How do you write a specification?

Specification information can be captured at any stage of the design process. Early client requirements and high-level building performance should be recorded and will develop over time into choices about the systems and products needed, and description of their performance against standards, key properties, and manufacturers. Specification platforms like NBS Chorus provide template clauses for a range of system types, kept updated with the latest references, and allow you to issue published versions of your work at key project stages.

3. Why are specifications important?

Almost a third of projects enter dispute*, most commonly between clients and contractors, and a quarter of those are linked to poor or missing specifications. There are many examples of building failures resulting in death, injury, and loss. Tragedies like the Grenfell Tower fire have brought increased scrutiny to the process of developing robust, high-quality building information across a project timeline and updating it during the use of the building or asset. Specification information forms a key part of this ‘Golden thread of information’ and developing an accurate, up-to-date specification gives you confidence in your design information, and can protect you from risk and future disputes.

The UK Government Construction Playbook, capturing key policies for how public works projects are procured and delivered, highlights the importance of specification to drive continuous improvement, record sustainability targets, and promote innovation.

*NBS National Construction Contracts and Law Survey 2013

4. What are the types of specification?

Different types of specification can be used at different stages of a project’s development. At an early stage, requests from the brief and high-level design ideas can be captured as an Outline description, then requirements of the building, systems and products can be specified in performance terms in a Descriptive or Performance specification, such as the acoustic, thermal, or structural requirements, and the specification further developed into more Prescriptive clauses selecting the standards, grades, and materials of component products. Proprietary specification includes product information like range names, reference codes, and key properties selected from manufacturer choices. The specification is often developed in tandem with Preliminaries, managing the contractual and project-wide requirements, and will continue to evolve as changes are requested, eventually forming handover data, for example as a record specification.

The development of the specification over the project timeline and an example of defining design responsibility is covered in this article and webinar on the RIBA Plan of Work 2020. In most cases, the project specifications will combine outline, performance (descriptive), prescriptive and proprietary information.

5. How should specifications be structured?

A consistent structure is essential to help others understand the requirements written in the specification and navigate their way through the information. Content in the specification can be structured in different ways. Using a digital platform will help you to achieve this easily with accurate and up-to-date codes. NBS Chorus uses the classification Uniclass 2015, as indicated in the UK annex of BS EN ISO 19650-2, but also supports CAWS, and alternative local structures for Canada and Australian markets.

You can find out more about the differences between Uniclass 2015 and CAWS.

6. What is included in a specification?

The specification information describes in words things that cannot be visualized or explained in drawings and the model. The content can include site requirements, contract information, client requests, performance criteria to be achieved, the quality of products needed, references to various standards applicable to the materials and systems selected, how work is to be completed and tested, and maintenance of the building in-use.

Some dimensions, for example tolerances or coating thicknesses, may be specified but the specification is not the best place for visual information like more complex dimensions, positions, and geometry, or lists of schedules and quantities, which should be captured in the model instead to allow for more accurate pricing and cost information.

The (3D) model cannot not replace the specification, as some items will never be modelled, and performance, standards, and execution requirements are not captured. Notes on the drawing outputs are not a replacement for a well-written specification.

7. How do I write a good specification?

There are seven key principles to writing a robust specification, which NBS call the 7 Cs of specification:

  • CLEAR: Use clear, plain language and short phrases to list requirements. Avoid ambiguity to improve understanding for all users (not just lawyers).
  • CONCISE: Don’t include information that isn’t required or relevant – make the specification project-specific. If in doubt, leave it out!
  • CORRECT: Clarify requirements, refer to outcomes, and reference current BS, EN, or ISO standards wherever possible.
  • COMPLETE: Check the depth of information is appropriate. Only address the contractor, don’t specify differently for sub-contractors or manufacturers.
  • COMPREHENSIVE: Ensure all aspects of the project are covered – “say it once, in the right place” and use cross-references to avoid repetition or conflicts. NBS template clauses and Masters functionality is there to help you.
  • CONSISTENT: Use standard structure, terminology, and style. Keep outputs neat when published, so they are easy to navigate and understand for all receivers.
  • CO-ORDINATED: Ensure that drawing references in the specification are kept to up-to-date to match model annotations and other contract documentation.

8. Why should I use NBS to write specification information?

NBS have been producing specification content and manufacturer information for nearly fifty years. Every day, our authoring teams research, author, and maintain the NBS technical information, guidance, references, template clauses, and product data via our industry-leading software platforms, NBS Chorus and NBS Source.

NBS Chorus provides a consistent, standardized structure for your specification, pre-authored options and relationships, technical guidance in context including links to reference standards using the Construction Information Service, up-to-date product information, contractual information, the ability to develop your own Master content for re-use on similar projects, improved teamwork and collaboration features, security and access permissions to your project data, and a range of publication outputs and styles.

This article provides a comparison of NBS and trying to write specifications in Microsoft Word.

Find out more about NBS Chorus training on the NBS Academy site.

9. How does specification fit into BIM process?

The BIM process is about the creation of an information model from a range of platforms and inputs, including the specification data. Integrations with Autodesk Revit, Graphisoft ArchiCAD, and Vectorworks, and common data environments like BIM 360 and Viewpoint, allow designers to work in parallel with the development of model-based information and refer to specification requirements in the model environment. The key is using consistent references to allow annotations and embedded properties to link to relevant clauses precisely and accurately, indicating where critical information exists in the specification about the design or client requirements.

Features in NBS Chorus to collaborate with project team members, name files consistently, record a publication history, keep content updated, compare changes between versions, and access structured manufacturer data, all support standardised BIM process and the digital evolution of the built environment industries.

10. Where can I find examples of building specifications?

You can download sample templates of construction specifications using the standard NBS Chorus structures. The actual content of your specification will be project-specific, but these samples demonstrate the quality, well-structured, look and feel of outputs created using NBS Chorus to reference external standards as part of a consistent database of information.

Further information