You must use a different GTIN for each package size of the products you sell to the building materials trade. This is important because different package sizes have different trade item information, which helps with finding them in databases and other sources.
To make the whole information and product flow better within the circular chain, including your own processes, you need to give unique GTINs to all packaging levels and sizes that you manage. The faster you do this, the sooner we can all enjoy the possible efficiency benefits.
Learn more about GS1 standards for the identification of construction products.