Note: this article focuses on the Uniclass classification structure in its examples; however, a CAWS version of the early-stage library is also available. The broad principles of this article apply both to the Uniclass and CAWS approach.
Early-stage specification
Typically, an NBS specification is developed during the technical design stage of a project. A specification can have many purposes. However, the fundamental purpose of developing an NBS specification is to define quality levels at the point of tender and for this document to be then used to verify this quality during the construction and handover phases of the project.
Based on customer feedback, NBS has now released additional specification content that can be utilized far earlier in a construction project. The new ‘early-stage specification library’ from NBS allows the specification process to start as part of the concept design process by defining requirements at an elemental level. Figure 1 below shows that, typically, the technical specification writing would start towards the end of RIBA Stage 3 when the required specific systems and products that form the design are understood. However, prior to this, the elements that define the spaces in a building are designed and documented at a much earlier stage.
Consider the concept design in Figure 2 below. The activities that will take place in the building and the spaces required to deliver these will be understood from the brief. The concept design will then comprise of a combination both of these spaces and the elements that enclose them.
In this example, the wall elements have been split into different types based on the varying requirements of the spaces they enclose. It can be seen that the walls around the restaurant area and the walls around the back-of-house spaces are given individual project type codes.
At this early-design stage, the specification is likely to be very light. It would contain classified elements with unique project reference codes, a note defining locations, a short description and notes highlighting the relevant parts of the client brief. Figure 3 below shows example specification content that illustrates this.
In addition to the elements specified by the architect, the landscape architect, structural engineer and building services engineer can add specification requirements against the various elements and ‘functions’ that further define the environment of the space. Examples of typical elements and functions are provided below in Table 1.
It is expected that the architect, undertaking the role of the lead/ principal designer would coordinate the production of a multi-disciplinary document in which all elements and functions are developed. The collaborative nature of the NBS Chorus specification platform is designed to enable this.
| Item | Definition |
| Element | Used to enclose and form a space and define the environment in the space. For example, floor, roof, openings or walls. |
| Function | Used to refine, manage and control the environment in the space. For example, heating or cooling. |
Dr Stephen Hamil, Innovation Director and Gordon Gray, Technical Author from NBS present an overview of early stage specification content in NBS Chorus
Fixing the performance requirements
A key part on any project is defining and fixing the requirements of the elements that make up the building. For an element such as an external wall, this could be the fire performance, the energy performance or the acoustic performance. Once this performance is fixed, it should remain as a constant requirement that all later design decisions are referenced back to.
In the example in Figure 4 below, the wall element has the requirement of 0.35 W/m2K U-value and 90 minutes for fire performance. These performance requirements must now be met by any combinations of system and products that are specified at a later stage in the project.
The outline specification clause item gives an indication of the systems and products that are being considered. These items may change as the design develops, but the elemental performance requirements should not.
Notes may also be added to share with other consultants; the example in Figure 4 below contains notes concerning how the project budget or sustainability aspirations are being taken into consideration when developing the concept.
Keeping within the project budget
Two of the many challenges for any design team are: (i) ensuring that any proposed design remains within the project’s budget; and (ii) considering the carbon impact that will result from the systems and products that are specified.
In developing the NBS early-stage specification library, we are working in partnership with Building Cost Information Service (BCIS) to deliver indicators to the design team to help address both of these issues. The most important time to influence cost and carbon is the concept design stage, and the specification is a key document. Once a project has reached the technical design stage, then the ability to influence cost and carbon is significantly reduced.
Figure 5 below illustrates how data on construction cost, ongoing maintenance and replacement costs, and embodied carbon are displayed against each element. Designers can use these indicators to help influence their specification decisions and then record the BCIS reference code for collaboration with cost consultants (who are developing the cost plan) and sustainability consultants (who are developing whole life cycle carbon assessment models).
Developing the technical solution
Figure 6 below provides an example where the constituent systems have been selected that will meet the performance requirements and any design requirements of the element. In this example, these have only been added as ‘placeholders’ in NBS Chorus to keep the specification as short as possible.
It can be seen that rainscreen cladding, a masonry leaf and an internal tile wall system have been specified to achieve the required performance.
In terms of other key project documentation/ information management, it is expected that the design responsibility matrix would be updated at this stage. This would provide clarity over: (i) which discipline has the responsibility for developing the technical solution for each element (for example, a structural engineer may specify the concrete deck system of a floor, but the architect would specify the floor cover); and (ii) which systems will be included in specialist sub-contractor design portions and which systems will be fully prescribed by the design team.
Figure 7 below shows that, ultimately, the early-stage specification provides a ‘table of contents’ for the systems within the technical specification. In NBS Chorus, the specifier can click on the rainscreen cladding hyperlink and open this system for editing. They can then finally define the products that make up this system.
The parent element references are clearly displayed at the top of each system within the technical specification. This clearly shows which elements the system is part of and provides clarity to the specification author, as well as to any recipients of the published document.
Completing a technical specification that is cross-referenced back to the original early-stage specification has a number of benefits:
- ‘Over-specification’ can be avoided. For example, if insulation is included both in the cladding system and the masonry system, then this could lead to the energy and acoustics performance for the element being well above the required minimum. 'Offering visibility’ of the systems together as part of the whole wall element helps the specifier to minimize duplication and omission in the individual systems.
- Verifying the technical design in order to more easily demonstrate that compliance with the Building Regulations has been achieved and that the original performance requirements have been met. Under the new building safety regime, to ‘demonstrate compliance’ is a key duty of the principal designer prior to construction starting.
- Assessing any proposed substitutions of systems or products during the construction stage. Any changes that are proposed must not result in the new solution no longer achieving compliance with the Building Regulations or no longer meeting the original performance requirements. Again, this is a key duty both of the principal designer and the principal contractor under the new building safety regime. Robust change control and the maintenance of a digital golden thread between building starting and occupation is an essential task of any project team, and this will be monitored by the Building Safety Regulator on higher-risk buildings.
Libraries available from NBS
Two early-stage specification libraries are available from NBS:
- Uniclass – element and function specification templates and associated guidance are included. This content is classified using the Uniclass EF table. BCIS cost and carbon data are provided within the guidance. Functionality is provided in Chorus to link elements and functions to the systems that are developed in the technical specification.
- CAWS – ‘Construction’ specification templates and associated guidance, covering a similar scope to Uniclass, are included. BCIS cost and carbon data are provided within the guidance. Due to the structure of the content, text references are required to relate a construction with the relevant clauses within the constituent work sections. For example, this follows the way in which a text reference would be used to relate clauses in F10 to clauses in F30 or Z10.
Follow the link below to find out more about the early-stage specification library.
