The NBS specification clause is the document that formally defines the flooring product for a construction contract. What you write in the clause determines what the contractor is obliged to supply — and what the client is entitled to receive. A poorly drafted clause leads to substitutions, disputes, and floors that do not perform as intended.

This guide covers how to write a clear, complete NBS clause for commercial gym flooring, with specific guidance on the sections most frequently drafted incorrectly.

NBS Clause Structure

A flooring specification clause in NBS format typically comprises several sections. The exact structure depends on whether you are working in NBS Chorus (the current platform) or an older NBS format, but the core content is consistent.

Products Section

This is where you name the product. The common mistake here is specifying by generic description rather than product reference — "20mm rubber tile, recycled content minimum 80%, black" is not a specification: it is a performance requirement that any number of products could technically meet, including ones that will not perform adequately in use.

Best practice is to name the manufacturer, the product, and the product reference, then add performance requirements as supplementary conditions. For example:

Example clause extract: "Rubber floor tiles: Superstrata Pulse, 20mm thickness, 1000 × 1000mm, colour: Anthracite. Performance requirements: EN 13501-1 fire classification Cfl-s1 minimum; Shore A hardness 55–65; shock absorption minimum 40% to EN 14808. Or equal approved — submit sample and test data for review prior to procurement."

The "or equal approved" provision is important. It tells the contractor that substitutions will be considered but must be formally approved — which gives you control over what actually goes in the floor.

Execution Section

The execution section covers installation requirements. This is where most clauses are weakest. For rubber gym flooring, the execution section should address:

  • Subfloor preparation. Maximum deviation under a 2m straightedge (specify 3mm). Moisture content limits if adhesive is being used. Surface regularity and any self-levelling compound requirements.
  • Acclimatisation. "Allow materials to acclimatise to the installation environment at 18–22°C for a minimum of 24 hours prior to installation."
  • Installation method. Free-lay interlocking (for tiles), loose-lay with perimeter fixing, or fully bonded. The choice affects performance and future removability.
  • Joint treatment. For roll rubber, specify butt joints and the type of adhesive or tape used at seams.
  • Interface details. Reference the zone transition details. Specify transition profile type at junctions between different products.
  • Protection. "Protect installed flooring from damage by subsequent trades. Lay protective boarding over finished surfaces before continuing fit-out works."

Performance Section (Where Required)

For upper-floor installations with acoustic requirements, add a performance section that cross-references the acoustic specification. This section should name the target L'nT,w value, reference the acoustic underlay product and thickness, and require post-installation testing if specified.

Including Fire Test Data

The fire classification for the flooring product should be referenced in the clause and the test certificate included in the specification package. The clause should state: "Fire classification: Cfl-s1 to EN 13501-1. Test certificate from [test laboratory] reference [certificate number] to be provided to building control."

Do not simply state the fire classification without referencing the test evidence. Building control officers increasingly ask for the certificate, not just the declaration.

Superstrata NBS Clauses

Pre-written NBS-format clauses for Titan, Pulse, Stride, Shield, Tundra, Runway, Court, and Dojo are available as part of the Superstrata specification pack. These clauses are drafted for insertion into NBS Chorus and include product references, performance standards, and execution requirements.

If your project has specific requirements — non-standard colour, bespoke thickness combination, acoustic performance target — contact the specification team and we will draft the clause accordingly. We typically return a draft within 24 hours of receiving the project brief.

A Note on Proprietary Specifications

Public sector projects, and many larger commercial developments, require the specification to be non-proprietary — that is, it cannot name a single manufacturer without providing an approved alternative. The NBS clause format accommodates this through the "or equal approved" provision described above.

For projects where a genuinely non-proprietary specification is required (for example, a local authority framework or an OJEU-procured contract), the clause should be written to performance standards with a reference product as the benchmark. Superstrata can provide the performance data needed to write a clause to this format. Contact the specification team with the project details and procurement requirements.