We are producing a stage 3 then onto a stage 4 specification for the production side of the design and build process. Q: do we need to include several alternative products or suppliers within the specification.
In terms of ‘need’ to include several alternatives, this should be addressed by the Scope (Works Information) or by reference to what each design stage deliverables are specified, not by the conditions of contract.
By stage 3 and stage 4, I presume that you are referencing back to the RIBA Plan of Work stages. In my experience the specification would state a British or other applicable standard and may also specify a particular product often with the words ‘or equivalent’ added so as not to limit the use of one product.
‘Need’ is a strong word. You ‘need’ to state the magical words “or equivalent” if subject to EU Procurement Regs unless you have already run an EU compliant competition.
So if your client is in the private sector, then you do not ‘need’ to.