What is the ruling on building a house by installments through a bank if the bank signs a construction contract with the contractor after the client signs the contract with the bank?

This transaction falls under the category of 'Istisna' (manufacturing contract). Its essence is that a person requests another to manufacture something that does not currently exist, according to specified descriptions and materials, and for a financial sum. The contract requires clarity of all specifications to avoid dispute, such as the manufacturing material, its source, its description, its quantity, and the delivery date. There is no objection to the bank requesting a contractor to agree with them on the construction.