NBS Chorus vs SpecifiedBy: What’s the Difference and Which One Do You Need?
These two platforms come up regularly in conversations about construction product specification. Both sit in a similar space, used by architects and specifiers. Large data businesses in the UK construction industry also use them.
But they are not the same thing, and comparing them directly misses the point.
We explore what each platform does, who it’s built for, and how they fit into a typical specification workflow. I have never been a customer of either platform. Everything here is based on publicly available information that we have independently researched, with sources cited throughout for transparency.
What Is NBS Chorus?
NBS Chorus is a cloud-based specification writing platform. It’s built for architects, engineers, and specification writers who produce technical project specifications.
NBS (National Building Specification) has been part of the UK construction industry since 1973. RIBA (Royal Institute of British Architects) originally owned it before passing it to Byggfakta Group. Hubexo, a global construction data and software company, currently holds ownership. [1]
Chorus replaced the older NBS desktop software and moved the product into the cloud. The core functionality is writing specifications, not finding products.
Key features:
- Over 15,000 pre-written, regularly updated specification clauses in Uniclass and CAWS formats [2]
Real-time collaboration so multiple team members can work on a specification simultaneously
BIM integration with Autodesk Revit, Graphisoft Archicad, and Vectorworks [2]
Office master specifications to maintain consistency across projects - Digital audit trails
- Integration with NBS Source, a separate manufacturer product library (more on
- this below)
NBS Chorus is purpose-built for the specification writing stage of a project. Its value is in the structured, standardised output it produces and the way it connects to BIM workflows.
What Is NBS Source?
NBS Source is a manufacturer product library that sits inside the NBS ecosystem. Manufacturers list their products, technical data, BIM objects, and CAD files in Source. Architects using NBS Chorus can browse Source and pull products directly into their live specifications with a single click. [4]
According to NBS, 98% of the AJ Top 100 architectural practices use NBS to write their specifications. [4] That makes NBS Source a significant route for manufacturers wanting their products to reach specifying architects.
Source is free for specifiers to browse. Manufacturers pay to list.
What Is SpecifiedBy?
SpecifiedBy is a product research and discovery platform. It is not a specification writing tool. It is a place where architects, designers, and specifiers go to find and compare building products early in the design process.
Causeway Technologies acquired SpecifiedBy in 2021. Causeway is a well-established UK construction software business. [5]
The platform lists over 2,600 manufacturers and more than 116,000 products across 20+ product categories. It has reported over 70,000 active monthly users. [5]
Key features:
- Search and filter building products by category, performance criteria, and technical requirements
- Side-by-side product comparison
- Access to technical data sheets, CAD files, and BIM content
- Free for specifiers to sign up and use
- Manufacturers pay to list products and access lead generation data
SpecifiedBy is positioned at the research and early specification stage. A specifier uses it to understand what products exist in a category, compare options, and shortlist candidates before those products are written into a formal specification.
The Core Difference
NBS Chorus is a specification writing tool. SpecifiedBy is a product research tool.
They serve different stages of the same workflow.
A specifier uses SpecifiedBy to identify and compare rooflight products early in the design process. They shortlist two or three options. They then move into NBS Chorus and write the formal project specification, pulling in product data from NBS Source.
SpecifiedBy and NBS Source are the more direct competitors. Both are manufacturer-facing product databases used by specifiers to find products. NBS Chorus is in a different category entirely: it is the tool where the specification document itself gets written.
Manufacturer Perspective
If you are a building product manufacturer trying to reach architects who specify, both platforms are relevant but for different reasons.
NBS Source puts your product inside the workflow of architects who are already writing specifications. Chorus’s integration allows you to add your product to a live spec at the click of a button. Given that 98% of the UK’s top architectural practices use NBS, the audience is concentrated and highly relevant. [4]
SpecifiedBy gives you broader reach at an earlier stage. Specifiers use it when they are still in research mode, comparing options. Over 70,000 active monthly users is a meaningful number, and being visible at the research stage matters. [5]
Neither is a silver bullet. If you’re listed in NBS Source, this may not guarantee specification. Being found on SpecifiedBy does not mean a specifier will follow through. Both require strong product content: accurate technical data, downloadable files, and clear performance information.
Specifier Perspective
The choice between these platforms is largely determined by what you’re trying to do as an architect or specifier.
NBS Chorus is the right tool if you need to produce a structured, auditable, BIM-linked specification. It is the industry standard for a reason. The upfront cost is significant, particularly for smaller practices, but the clause library and BIM integrations are genuinely useful.
SpecifiedBy is worth using when you are in early product research mode. It is free, the database is broad, and the comparison functionality saves time. It does not replace a specification writing tool.
The two platforms are not mutually exclusive. Most specifiers will find themselves using both, just at different points in the process.
A Note on Integration
NBS Chorus and SpecifiedBy do not directly integrate with each other. Products found on SpecifiedBy cannot be pushed into an NBS Chorus specification in one click. That direct workflow exists only within the NBS ecosystem, between NBS Source and NBS Chorus.
If streamlined specification workflows from product discovery to written spec are a priority, the NBS Source and NBS Chorus combination is the more joined-up route currently.
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| Summary | NBS Chorus | SpecifiedBy |
|---|---|---|
| Primary Function | Specification writing | Product research and discovery |
| Owner | Hubexo | Causeway Technologies |
| Cost to specifiers | Paid subscription | Free |
| Cost to manufacturers | Via NBS Source listing | Paid listing |
| BIM integration | Revit, Archicad, Vectorworks | CAD/BIM file downloads |
| Best used at | Detailed design and specification stage | Early research and product comparison stage |
| Integrate with each other | No direct integration | No direct integration |
The Bottom Line
NBS Chorus and SpecifiedBy are not direct alternatives. Asking which one you should use is a bit like asking whether you need a drawing package or a reference library. You probably need both, just at different times.
For manufacturers, the more useful question is which platform puts your product in front of the right specifier at the right moment. NBS Source wins on depth of integration into the specification workflow. SpecifiedBy wins on breadth of reach in the early research stage.
For specifiers, NBS Chorus remains the dominant standard for specification writing in the UK. SpecifiedBy is a genuinely useful free tool for product research that complements rather than competes with it.
Sources
[1] Wikipedia — National Building Specification: https://en.wikipedia.org/wiki/National_Building_Specification
[2] NBS Chorus product page — features overview (via thenbs.com)
[3] User-reported NBS Chorus pricing, sourced from community discussions and published reviews (pricing not officially published by NBS)
[4] NBS manufacturers page — “98% of the AJ Top 100 architects use NBS to write their specifications” (manufacturers.thenbs.com)
[5] Causeway Technologies / SpecifiedBy — platform overview and user statistics (specifiedby.com and causeway.com)
Frequently Asked Questions
What is NBS Chorus?
NBS Chorus is a cloud-based tool for creating technical construction specifications, currently owned by Hubexo as the successor to NBS’s earlier desktop software. It allows specifiers to access over 15,000 pre-written, regularly updated specification clauses and integrates with major BIM software.
What is NBS specification?
NBS specification generally refers to a process of writing formal construction specifications using NBS’s platform and its library of standardised clauses. It is considered a critical distribution channel for manufacturers whose products get specified into projects.
What is SpecifiedBy?
SpecifiedBy is a product discovery and comparison platform that was acquired by Causeway Technologies in 2021. It currently hosts over 2,600 manufacturers and more than 116,000 products across 20+ categories. It’s aimed at the early-stage research phase rather than formal specification writing.
What’s the difference between NBS Chorus and SpecifiedBy?
SpecifiedBy is for early-stage product research and discovery, while NBS Chorus is for writing the formal specifications once decisions are made.
Do NBS Chorus and SpecifiedBy integrate?
No, there’s no connection between the two platforms.
Should manufacturers prioritise NBS Source or SpecifiedBy?
Both of them matter for different reasons. NBS Source offers deeper integration into the specification-writing workflow that architects already use. On the other hand, SpecifiedBy offers broader visibility at the earlier research stage. Most manufacturers will benefit from a presence on both.
Should specifiers use NBS Chorus or SpecifiedBy?
Most use both at different stages of their project. SpecifiedBy is a free tool for early product research, and NBS Chorus is the standard platform for writing the formal specification at a later stage. They complement each other rather than acting as alternatives.