If the lease expires and the landlord wants to terminate, he doesn't need to give you any notice. However, it is normally communicated to the tenant. 30 days notice is very common but your lease agreement should indicate how long. Many lease agreement says, "it will automatically be renewed as month to month after lease term expires if neither side gives notice." So I would recommend referring to your lease agreement. If you haven't heard back from your landlord, try following up via e-mail and phone call.