Article 44 A contract established according to law shall take effect upon its establishment. The entry into force here mainly refers to the contract concluded in written form and signed by both parties in accordance with the provisions of laws and administrative regulations.

Article 37 If a contract is concluded in the form of a contract, one party has fulfilled its main obligations before the contract is signed or sealed, and the other party approves it, the contract is established.

According to the above provisions, if the seller has delivered the house, then even if no contract is signed, the contract is established.