I'm working in an old neighborhood in Seattle, the plat is from 1875, and was carved out of a Donation Land Claim, which is nice history but not entirely relevant other than why there is an odd ROW width or two nearby where the DLC met the PLSS world. The puzzler is how the adjoiner's house was built in the 1950s on a three foot setback. The client wants to put a fence on the line and the adjoiner has agreed in principal to put it on the surveyed line, but when the line was at three feet I said hold everything, I need to figure out how this happened. Interesting is that the existing fence is at five feet presumed setback. Raising the question, if the adjoiner agrees to "whatever the surveyor says" are they giving up their unwritten rights? Not that I am going to tell them, that would not be in the client's fiduciary interest, but I can and have explained the unwritten rights and the uncertainty to the client.
The house footprint is so close to parallel three feet from my calculated line that it was the clue that I should go look for an Ordinance. Today I found the Seattle Ordinances from 1920s-1957 that did indeed specify a 3 foot setback for that zoning area. So they did the right thing way back when.
The unwritten rights part is sketchy and there is not enough known to even think about it.?ÿ If the 5' set back has been accepted it would seem to be in both owner's interest to adjust the lot line, if zoning allows that with one seeling the two foot strip to the other.