10 August 2022

1. What is a specification?

Specification is the skill of documenting specific requirements about the work to be carried out on a building project. A construction specification is a well-structured, detailed description of the quality, standards, workmanship, materials, and completion of work, which evolves across a project. Specifications are usually prepared by architects, engineers, designers and specifiers. They may be published as part of the contractual documentation for building contractors, to be read in parallel with schedules, drawings and sometimes models, and later forming part of the handover information.

2. How do you write a specification?

A specification is a written document comprising a wide range of subheadings, usually called trade sections or work sections, which describe the work to be done by the contractor of the project. It will often refer to the drawings or schedules in the project and may feature preliminaries or addenda to provide further information, all designed to avoid discrepancy and ambiguity, so that the project construction runs smoothly. Specification information can be captured at any stage of the design process. From early stage client requirements through to high-level building performance; accurate details should be recorded and developed into specific choices about the systems and products needed. This will also include descriptions of their performance against standards, regulations, and manufacturer’s installation guidelines. Specification platforms like NBS Chorus provide template clauses for all building 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?

Building projects commonly enter dispute between clients and their contractors, and a huge proportion of those are linked to inaccurate or missing specifications. There are many examples of building failures resulting in death, injury, and loss. Serious incidents like the Lacrosse Tower fire in Melbourne or Opal Tower evacuation in Sydney have brought increased scrutiny to the process of developing robust, high-quality building information across a project timeline, and updating it during the operation of the building. Investing time into quality specification forms a key part of the ‘Golden thread of information’ in forming an accurate, up-to-date document to give you confidence in your design information, and protect you from risk and future disputes.

For example, the DBP Act (NSW) has introduced tighter controls on every step of the design and construction process in terms of documented and responsible product selection, all the way down to the manufacturing process. Specifications need to modernise, and be more active in terms of the choices that architects and designers make.

4. What are the types of specification?

Different types of specification can be used at different stages of a project’s development. In early project stages, requirements of the brief or concept design ideas can be captured as an ‘Outline’ description, then requirements of the building, systems and products can be specified in a ‘Descriptive’ or ‘Performance’ specification, such as the acoustic, thermal, or structural requirements. The specification can develop further into more ‘Prescriptive’ clauses, by selecting the standards, grades, and materials of component products. ‘Proprietary’ specification includes exact information like product 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 made, 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. This article from the AIA also outlines the importance of accurate and detailed specifications. In most cases, the project specifications will combine outline, performance (descriptive), prescriptive and proprietary information, as demonstrated below with cladding and doorset specification.


5. How should specifications be structured?

Generally, a specification is structured with ‘Requirements’ or ‘Scope of work’ at the start, followed by relevant regulations or contractor considerations. Often the materials, products and components can be documented next, and then finally describe the installation and completion instructions. This consistent structure will mean that each trade section is organised in the same logical way and is hence easier to read.

However, it is important to understand that each specification for each project will be different depending on the services that the designer is employed for. As long as the information is clearly shown in a logical manner, the specification will be a much more informative and useful document than it has been previously.

The below structure is adopted in SpecPack and SureSpec content.

Using a digital platform will help you to achieve this easily with accurate and up-to-date codes. Subscribers to NBS Chorus in Australia can access multiple classification sets that structure content in different ways, for every type and size of project.

These content sets, in order of breadth, are: Uniclass 2015, SureSpec, SpecPack and SpeedSpec.

The latest release from NBS Australia is SureSpec. The illustration below uses SureSpec as an example, which adopts the 4 digit NCS codes that are commonly recognised across Australia, along with trade section naming and the type ID options in Chorus.


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. This should be captured in the drawings and models 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. Similarly, performance, standards, and execution requirements are not captured buy the model, and hence need to be described. Notes on the drawings 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 AS 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 to the construction industry for nearly fifty years. NBS Australia has continued that work after commencing content writing here in 2013, and launching Chorus in 2019. 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 is a specification writing platform, allowing connected data to transfer through your project documentation, but using the spec as the central location. Chorus provides a consistent, standardized structure for your specification, with pre-authored options and relationships, technical guidance in context, including links to reference standards using the NBS Australia publications page. There is also 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.

NBS Source (soon to link with Archify) is our products and manufacturers website, allowing designers to instantly add pre-verified products to their spec, removing the need for trawling through manufacturer websites to find the right technical information.

This article provides a comparison between NBS Chorus and writing specifications manually in Microsoft Word. You can find out more about NBS Chorus plans and features here.


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 Revit, ArchiCAD, and Vectorworks, along with 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 inside 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.

There are 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. Specifications have to work harder and be more flexible, to justify the amount of time spent on them. It’s a crucial time for this digital evolution of the built environment.

10. Where can I find examples of building specifications?

You can download sample templates of construction specifications demonstrating the NBS Chorus content sets. The final 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

  • Find out more about NBS Chorus
  • Find out more about NBS Source
  • An introduction to specification writing (CPD) - 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.