If one was to re-use an architect’s copyrighted design, without getting another licencse or paying fees, what does a standard JCT do about this?
You are not allowed to do that as standard JCT contracts provide that the design or IPR’s remain with the Architect. You will need consent to use the IPR.
What factors decide whether they are infringing on the Architects IPR
Multiple IPR protections may apply to a single product, including; registered design, unregistered design, trademark, patent and copyright, including the application of these in a particular ‘territory’, as well as the enforcement rights of an unregistered design following Brexit.
IPR is a specialist subject and you would be well advised to seek particular advice on this matter.