Is it permissible to engage in an installment transaction for construction or finishing materials that the engineer purchases for the client, provided that 2% per month is added to the original amount according to the agreed-upon repayment period?

This transaction is impermissible if the engineer does not sell the materials to the apartment owner, because it involves explicit usury (riba), as the engineer imposes a usurious interest that multiplies monthly, which is forbidden by Islamic law. The transaction can be corrected by the financier purchasing the materials, bringing them into his possession and responsibility, and then selling them to the customer at a higher price, provided that this price does not increase due to delayed payment or the imposition of a late penalty.