You can take a loan from the bank even if the property is in your father's name. In that case you can either take personal loan for certain amount or you can take home improvement loan as a co-applicant with your father. The eligibility for the loan will be particularly depend on the amount of loan you will need and also the bank requirements. I am giving you a general list of documents you would require, rest the bank would be able to guide you further depending on the need and present circumstances.
Generally, you would need following documents:
1. Identity Proof: Aadhar Card, Voter's ID card, Driving License, valid passport.
2. Proof of Income: Your father's pension proof.
Your last three month's salary statement
Last six months bank statement.
Last ITR and Form -16.
3. Ancilliary documents: You would need your and your father's passport size pictures in case of home renovation loan. Cheques
4. Specific to Home improvement related documents:
All the original deeds of the house
Proof of no encumbrances on the property
An estimate for proposed work from an Architect / Civil Engineer.
Your second worry is about your sister claiming in the property. That would arise in the instant your father dies without a will. If he leaves a will in your name or equal distribution between you and your sister, then such question does not arise. You can also discuss this with your sister before you go for renovation and take a No Objection from your sister,
I hope this responds to your query, if there is any thing else feel free to get in touch.
Regards,
Richa Bharadwaja