If you can material bills and construction contract given money via bank transactions. Those bills can be produced in the court and till what your father has did with the mortgage loan amount.

Date of disbursement of loan amount and material purchase or amount distributed to those people like merchant and contractors etc.

You need to show relation of source fund with the loan account to the expense made for construction by your father 

Payment made to contractors for construction of building , for purchase of cement , steel other raw materials will help you prove it was used for construction of building 

bank statements would show the fund transactions made of loan amount 

The bills paid for the buying construction materials and the labor charges will be substantial documentary evidence to prove your case,.

If you have a labor contract agreement or construction contract agreement between you and the contractor, you can utilise that also.

Dear client,

Proving the utilization of the loan amount for the construction of a building, especially in a legal context, requires documentation and evidence.

Documentation:
Review the loan agreement or documents related to the loan. It should ideally specify the purpose of the loan. If it explicitly mentions the construction of the building, that serves as evidence. Gather bank statements showing the transactions involving the loan amount. These records should indicate withdrawals or transfers linked to the construction work, such as payments made to contractors, purchase of construction materials, etc. Any invoices, bills, or receipts related to the construction can serve as evidence. These documents should ideally match the timeline and amount of the loan disbursement. Any communication (emails, letters, etc.) between your father and relevant parties (builders, contractors, suppliers) discussing the utilization of the loan for construction purposes can be valuable. If there were individuals involved in the construction process who can attest to the fact that the loan was indeed used for building purposes, their statements can support your claim.

Survey of Loan Amount:
The "survey of loan amount" is not a standard legal term in Indian law. However, you might be referring to substantiating the utilization of the loan amount for the intended purpose, which involves providing evidence (as mentioned above) to showcase the correlation between the loan and the construction.

You can reach out to us for further assistance

- Under the Hindu Law, a son is under a pious obligation to discharge his father's debts out of his ancestral property regardless of the possibility that he had not been profited by the debts.

- Further, if the debt is purely personal debt of the father, then it cannot be passed over to the legal heirs.

- Further, if you got property of father both movable or immovable properties through inheritance then only, your liability to pay the debs, after selling those inherited property.

- Further, after the demise of father , the bank can recover the amount of loan from guarantor , and in his absence the amount can be recover by the legal heirs of the deceased. 

- You can submit the proofs before the Court to prove that the amount for personal in nature as it was taken by him for the construction of the building.