Legal Question in Real Estate Law in California

If true, you have a claim against the title company, prior owners, etc to make them remedy the problem. You'll have to confirm your suspicion with a formal survey of the property. These situations can frequently be worked out informally with property line realignment via deeds. Get a local attorney experienced in real estate.

Mr. Nelson is right that these things are usually worked out informally, and that before you do anything, you should get a professional survey. There's a good chance your measurements are off from what a formal professional survey would show, especially if the land is not perfectly level for example. Slopes are measured for survey purposes as if viewed from the sky. So based on the simplest example of the pythagrean theorum: a 3x4x5 triangle, every four feet surveyed could be five feet measured with a tape on the ground.

If there is an encroachment, there is a process called a lot line adjustment that is usually worked out between the neighbors. It will probably require city or county approval, though, so don't just go recording deeds with new lot line descriptions, or you could run afoul of the Subdivision Map Act. As for who's responsible, Mr. Nelson is wrong that you have a claim against your title company. Unless you specifically asked for and paid a lot extra for a policy endorsement, your title insurance excludes encroachments and anything else that a professional survey would have disclosed.