After scandal revelation: German company “strongly” rejects allegations about rebuilding Mariupol. The EU's sanctions against Russia are extensive.
Building materials are not listed as sanctioned by the EU. However there are several areas that capture the sanctions that the activities of Knauf and WBK Systems could fall away to. For example: “In order to order a building to fall away from reality, you need to take away the order to take the building away from you.”