Re: How to File for Adverse Possession for My Own Backyard
Yes, get an attorney immediately. You should also have another survey done as a second opinion. Boundary surveys are not often cut and dried technical exercises resulting in a very definite line all surveyors would agree on, but more often are a study of documentary and physical evidence. If a surveyor who may be an excellent measurer but is not very familiar with the rules regarding boundary evidence performes a boundary survey, he may rely on evidence of lesser value (recited dimensions in a deed are normally among the lowest) over evidence of higher value (monuments of prior surveys, and sometimes, even long standing lines of occupation - fences, edges of patios, etc.). Find a surveyor whose main practice is boundary surveying as opposed to construction.
California does allow tacking, so it is when the improvements were built, not when you purchased the property that counts for the time. But before you go to AP, ensure that the survey was correct by having your own performed.
I'm a surveyor, not your surveyor & not an attorney.
Advice is general survey, not legal. Hire a local professional for specific advice.