I live in Washington State. We bought a 2 acre lot in 2001 and started construction in Feb 2002. The neighbor on one side was a couple months ahead of us on construction and finished his house and landscaping before we did. The realtor had rebar stakes on the lot lines with a little white board with arrows showing Lot 3 on one side and Lot 4 to the other side. The neighbor put in his sprinklers and shrubs a bed with fairly close adherence to this property line. I did the same and life's been good.

Now I have built a shop. The builder, wanting to comply with the county requirement of 15' layback, placed the building 25+ feet from this line. Well the neighbor does not like my shop and says that it "looks" right into his backyard, where he happened to put a swimming pool last summer. Because they are ticked off they had a survey done, and lo and behold the pin for our property line is about 20 feet in my direction. It seems there was a curvature pin for the road that the realtor assumed was the property line pin. Even the power company missed it because they placed the service box straddling the line. Mysteriously no one can find the original pin and the surveyor just drove in a new one.

My question is what legal grounds do I have to claim this property? The adverse possession statute for Washington State requires continuous and notorious possession for 7 years, for which I am a half year short. It's also questionable who has been paying the taxes on it. The assessor I'm sure is looking at the physical boundaries when he comes out, and does not reconcile that to the legal description. I've mowed it watered it, part of my driveway is on it, my utilities trench is on it, and now my shop is too close to the line. Oddly enough they said nothing till the shop was completed. How would a judge/arbitrator view this property line dispute?