” In California, is a prescriptive easement through notorious use automatic, or does it take place five years after the easement has been requested?”
The typical language used by the courts is that, in order to create a prescriptive easement, you must have “open and notorious use or possession that is continuous and uninterrupted, hostile to the true owner, and under a claim of right.” This use must continue for at least the statutory period, which in California is five years.
However, there are a number of ways to stop someone from getting a prescriptive easement, and possibly the easiest one is to give permission. If you’ve asked to use someone else’s property and the owner says yes, then your use isn’t “hostile,” and therefore the five-year period is not running. This is why you see those plaques that say “Right to pass by permission, and subject to control, of owner: Section 1008, Civil Code.” By putting the sign up, the owner proves that they’ve given permission, so no prescriptive rights ever accrue.
Also, ultimately, nothing is automatic. In theory, you get prescriptive rights after your five years is up, but in practice you just have the ability to assert those rights. If your neighbor fights it, you may have a long, nasty, and very expensive court fight ahead of you. Believe me, the best thing for both of you is to try your best to reach a compromise.