Hello,
We're having a kitchen installed partly in an existing edwardien buiding and partly in new built extension. Does the fact that there is brick walls coexisting with new built walls affect the requirement for trunking? What about if there are cupboards on all of one side of the old wall, is the metallic trunking still required? What is common practice and what is regulations imposed?
Ed

Please explain your interpretation of "trunking".

I assume it means bundling several cables together.

Once more than 3 current carrying conductors are bundled together more than 24 inches, those conductors will be subjected to derating factors, which can be a lengthy explanation.

Please get back with more detail, and where this building is located.