Fibre Reinforced Facade Encyclopedia: Design and detailing
NBS is the United Kingdom national building specification: a maintained library of specification clauses, delivered as a cloud platform, that a UK design team edits into a project specification. It was established by the Royal Institute of British Architects and is now run as a commercial platform. Alongside the clause library sits NBS Source, a product database that lets a specifier drop verified manufacturer data straight into the clauses they are writing. NBS is to the United Kingdom what NATSPEC is to Australia and MasterSpec is to New Zealand and the United States.
In NBS the specification and the product data are the same object. A specifier searching NBS Source for a cladding panel can insert the manufacturer clauses into the live specification without retyping anything.
At a glance
| Property | Typical value | Note |
|---|---|---|
| System | NBS Chorus | Cloud specification writing platform |
| Product library | NBS Source | Manufacturer data linked to specification clauses |
| Classification | Uniclass 2015 | Replaced the earlier Common Arrangement of Work Sections (CAWS) |
| Clause structure | Systems and products | A system clause with the products that make it up |
| Jurisdiction | United Kingdom and Ireland | Written against the Building Regulations and BS and BS EN standards |
| Fire references | Approved Document B; BS 8414 with BR 135; BS EN 13501-1 | Reaction to fire class is called up by clause |
| Regulatory context | Building Safety Act 2022 and the golden thread | Drives traceable, verified product information |
| Australian equivalent | NATSPEC | Same function, NCC and Australian standards (check the edition adopted in your jurisdiction) |
How an NBS specification is structured
NBS separates systems from products. A system clause describes the assembly, for example an open jointed rainscreen cladding system, and states what the assembly as a whole must achieve: wind resistance, water penetration, movement accommodation, reaction to fire, and the tests that demonstrate each. Product clauses sit under it and describe the individual components, the panel, the substructure rails and brackets, the membrane, the fixings and the cavity barriers.
This structure suits a rainscreen well, because the properties that matter belong to the assembly rather than to any one part of it. A panel with a good reaction to fire class installed over the wrong insulation in the wrong cavity is not a compliant wall. Naming the system first and then the components keeps that relationship visible in the document.
Uniclass and the classification layer
Uniclass 2015 is the UK unified classification system, with tables for systems, products, elements, spaces and activities. Every NBS clause carries a Uniclass code, which is what allows the specification to align with a BIM model: an object in the model and a clause in the specification can be tied together by the same code, so a change on one side can be traced to the other. Where a project runs an ISO 19650 information workflow, this is the mechanism that makes the specification part of the model rather than a separate PDF.
Uniclass replaced CAWS, the older Common Arrangement of Work Sections. Older UK specifications and older manufacturer literature still carry CAWS references, so check which the project is using before quoting a section.
What a manufacturer supplies into NBS
- A verified NBS Source listing: system and product clauses, with the properties populated rather than left as prompts
- Test evidence with the standard, the laboratory and the report date named, particularly BS EN 13501-1 reaction to fire and any BS 8414 with BR 135 full-scale result
- Weight per square metre, thickness, standard and maximum panel sizes, and finish range
- Substructure and fixing information, since the panel clause is meaningless without the system it hangs on
- BIM objects carrying the same Uniclass codes as the clauses
- Maintenance, cleaning and replacement information consistent with the stated design life
Why the UK specification is written the way it is
UK facade specification changed after the Grenfell Tower fire and the Building Safety Act 2022. The regulatory direction is traceability: a golden thread of information about what was specified, what was supplied, what was installed, and the evidence behind each. That pushes specification away from open descriptive wording and towards named products with current, verifiable test reports. Substitution has become harder to justify and product data that cannot be verified is increasingly rejected outright.
For a manufacturer this means the specification data set is not marketing collateral. It is a compliance record, and it needs to be as current as the test reports it cites.
Standards and references
- NBS Chorus and NBS Source (United Kingdom national building specification)
- Uniclass 2015 unified classification system; the earlier CAWS arrangement
- Approved Document B, Fire safety (England); the Building Safety Act 2022
- BS EN 13501-1 reaction to fire classification; BS 8414-1 and BS 8414-2 with BR 135
- CWCT Standard for Systemised Building Envelopes
- ISO 19650 information management using building information modelling
Related terms
Questions specifiers ask
What does NBS stand for?
National Building Specification. It is the UK national specification library, written against the Building Regulations and British and European standards.
What is NBS Source?
The manufacturer product database linked to the specification platform. Verified product data can be inserted directly into the clauses a specifier is writing.
What is Uniclass?
Uniclass 2015 is the UK classification system that codes systems, products and elements. NBS clauses carry Uniclass codes, which is how the specification aligns with a BIM model.
Does an NBS listing help on an Australian project?
Not directly. The clause structure is useful but the referenced standards are British and European. An Australian project needs NCC references and AS 1530.1, AS 5637.1 or AS 5113 evidence.
Is NBS the same as NATSPEC?
They do the same job in different jurisdictions. NATSPEC is the Australian national specification and references the NCC; NBS is the UK system and references the Building Regulations.
Working on a UK or Australian facade specification? ShapeShift supplies system and product data with the test reports that back each performance claim. Request specification data
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.