Stage 2 is the time to agree, and importantly sign-off, the architectural concept and engineering strategies, recognising that subsequent changes may be disruptive and compromise efficiency. Changing to a CLT structure at later stages will fail to realise many of the advantages of having adopted such an approach earlier (but is not uncommon). This stage is a good time to review and communicate the benefits of CLT use to ensure they can be realised wherever appropriate. If not already in place, a detailed design responsibility matrix should considered with appropriate experience and inputs sought as required.

Stage 3: Spatial coordination

The coordination of detailed engineering strategies (structural, servicing, acoustics and fire being the most relevant) with the architectural model is fundamental, as is optimising the design for manufacture. This will inform the cost and reduce subsequent risks, particularly when design responsibilities for such elements may change to suit a building contract. For this reason, teams may also wish to record further detail as to why decisions are made or particular approaches are adopted to avoid ambiguity should others become involved. Doing so can help prevent value engineering becoming simply cost cutting when the full benefits of CLT use are not understood. Well-developed BIM models and the use of benchmarks and mock-ups can help. Key deliverables for CLT projects will include coordinated designs for services installations and penetrations, typically ahead of those required for conventional builds.

Stage 4: Technical design

The RIBA Plan of Work advocates completing all the design information for manufacturing and construction before the end of Stage 4. Accordingly, the impacts of differing procurement strategies on design intent, information production and coordination (frequently most obvious in terms of building services) should be clearly communicated and understood by the project team and client and this is where previous experience or early stage collaboration can have great impacts.

Design and coordination responsibilities for all pre-manufactured elements will need to be revisited, allowing sufficient time when working back from the information required for panel manufacturing. Any design responsibility matrix should be reviewed and all parties should agree that unless exceptions are defined, and then carefully managed, the scheme for construction is frozen at this stage. Where information is required before the full completion of a stage, teams should be very clear about tasks required (and outstanding) and the responsibility for all associated deliverables.³

Appropriate design

This may include ensuring that material choices are appropriate to the intended function and likely form, addressing brief requirements or site conditions and that where possible the benefits of the material use are realised fully, accounting for issues of delivery cost, programme

and long-term value. Consider using CLT for its own strengths and characteristics rather than simply replacing another material and do not use it where it makes more sense to use other materials – it is certainly not appropriate for all circumstances or situations.