Is it permissible for a contractor to agree with the building owner on a price per square meter that includes materials and profit, provided that the building owner pays the cost of the materials to the contractor upon purchase?

The contractor's work, as described, falls under the category of permissible istisna' (manufacturing contract) subject to certain conditions. A contracting agreement is considered permissible whether the contractor provides both labor and materials (istisna') or labor only (an ijarah (leasing/hiring) on labor). The price may be fixed as a lump sum, or based on a unit measure, or on actual cost plus a profit margin, with the possibility of including a penalty clause. It is permissible to defer the entire payment or pay it in installments. Modifications and additions may be agreed upon, and the contractor is entitled to a customary compensation (awad al-mithl) if he makes additions with the permission of the employer without an agreement on a fee. However, if he makes additions without an agreement, he is not entitled to any compensation. The contractor is liable if he transgresses, neglects, or violates the terms of the contract. He remains responsible for his subcontractors. Stipulating the denial of liability or exemption from defects is not permissible. If it is agreed that the contractor will provide both labor and materials, it is permissible to receive payment in installments or for the cost of materials as part of the price, without changing the agreed-upon total price.