This lot has been cleared and the building plans are complete. Construction is ready to begin. No one involved in this transaction noticed the neighbors fence on the survey. The plans shows construction on top of the fence.
You need to compare your survey to your neighbor’s, there are two cases: 1) They concord and you simply ask your neighbor to move his fence (first nicely but the courts will support your view point also) 2) They do not concord and I would then put a hold on the construction before this issue is clarified. The builder has a strong incentive to solve that issue for you. The title company that closed your neighbor will need to be involved as well. This may not be a fast process.
I would ask neighbor for a copy of their survey and send a copy of yours and neighbors to each surveyor. Then ask both surveyors to review each and simply ask both who's is right?
Truth will come out! one surveyor might have to correct, then if any corrections are made, contact your title company and have them revise your title policy.
Then whoevers fence is wrong, respectfully move it if its a problem.
First, make sure the survey is accurate. How old is the survey? Who provided? If correct, it's up to the home owner and neighbor to decide the next course of action. After all, it's your neighbor. May be an honest mistake from long time ago.
If you were in the process of buying the house, I would ask the Seller to provide a Boundary Line Agreement with the next door neighbor explaining that the fence line is not the property line. If you currently own the home, it would be helpful to find out how long the fence has been there. Before you move the fence, make sure and have a surveyor mark the property line so that the fence is put on the Property Line.
Assuming that your survey is correct, you can request the homeowner to relocate the fence. Many times, the neighbor will produce their survey showing their fence line to be correct. As technology becomes more advanced and the locators are more precise, this situation is popping up more frequently - most often in older neighborhoods. Problems arise when the fence has been there for many years. Depending on the length of time and how the land was used, the neighbor may be able to claim 'adverse possession', entitling them to the land in dispute.