In California is a one year rental lease valid if the title owner of the
house did not sign it?
My father signed it for me, because I was not there, and I did not give him the power of attorney to sign for me nor is it in the lease.
Do it revert to a month to month tenancy because they are in the house now?
3 Answers from Attorneys
No, it is a valid lease. A court would most likely find that your father signed it as the ostensible agent of you. (Civ. Code, § 2300.)
I agree. Lots of leases are negotiated and signed by the agent of the owner, rather than the owner. Further, even if someone is not "officially" an agent of the owner, if they are "ostensibly" an agent, that suffices. If the lease causes you substantial hardship, you might try attacking the ostensible agency as not meeting the criteria set up in the Civil Code (section 2300). The outcome of such a lawsuit would depend upon facts and circumstances going well beyond what's given in your question. A power of attorney is unnecessary and would be unusual.
I agree with the above. On a more practical note if is is found invalid they may go after your dad for damages.