Building along the old fence line is not following a boundary. It is inheriting a stranger’s guess.

The old fence is evidence of nothing

This is the whole page. Fencing guidance is unambiguous that a fence does not define a property line and that only a recorded plat of survey or a professional survey does. The reason the existing fence is actively misleading rather than merely approximate is that it errs both ways: a fence company describes how in older neighborhoods fences can be a long way off, because some owners built well inside the line to avoid a dispute and others crossed it without knowing. Rebuilding along it means either giving away land you own or placing your fence on land you do not. The same applies to shrub lines, mowing patterns, driveways and the point where the grass changes.

A plat is not a survey, and the plat is what you already have

Almost every homeowner has a plat map from closing, and it is a reasonable starting point and not an answer. The distinction is put well in surveyor guidance: a plat map does not confirm where the fence line sits today, does not locate corner pins in the field, and does not tell you whether a neighbor built over the line or whether markers have moved. It is a record of the lot on paper rather than a fresh measurement of the land. A survey is field work: a licensed surveyor researches the deed, the recorded plat and neighboring parcels, then a crew visits and locates or sets corner monuments, typically iron pins. Only the second of those puts a mark on the ground you can build to.

Your fence contractor will not verify the line, and is not pretending to

Worth stating plainly because it is the most common misunderstanding in the transaction. A fence company explaining its own practice puts it directly: they will not verify the line, and they will not find it unless you have already marked it out or have a recent survey. They will ask for a plat, a survey or visible pins, and they will build to what you show them. They will not go hunting for pins unless you know where to look, and if things are unclear a good one will tell you to hire a surveyor first. The same source notes that some companies will eyeball where other fences and structures sit, and that this does not make it correct. The line is the owner’s responsibility and the build is the contractor’s.

Setbacks and heights are entirely local, and usually differ front to back

There is no national rule and guidance says so directly: setback requirements depend on the local county or municipal code and the zoning classification. Many jurisdictions permit a fence directly on the line in rear and side yards while requiring a setback of one to three feet in front yards, and corner lots frequently carry stricter rules for sight lines at intersections. Height works the same way, with many areas limiting front yard fences to three or four feet while allowing six to eight in back. This is a single phone call to the building department and it is the call that determines the design, so it belongs before the quote rather than after. Enforcement is real: setback violations can bring code action including fines and removal orders.

Consider building deliberately inside your line

A fence does not have to sit on the boundary, and in most areas you can place it a few inches or a few feet inside deliberately. There are two good reasons. The first is that it removes the encroachment question entirely, which is worth a great deal when the alternative is a dispute measured in inches. The second is more practical and less often mentioned: a fence set slightly inside your line means you can maintain both sides of it without stepping onto a neighbor’s property, which matters every time a panel needs cleaning, a post needs attention or something needs to be cut back. Losing a few inches of yard is a small price for both of those.

If the fence is meant to be shared, put it in writing

A fence straddling the line, or paid for jointly, or maintained jointly, is a different arrangement from a fence you own, and the difference matters years later when one party wants it changed or somebody sells. Guidance recommends documenting the location with a boundary line agreement, which helps prevent later challenges or demands to move the structure, and notes that where a fence is intended as a shared boundary most areas require the neighbors to agree in writing before building. The conversation is much easier before construction than after, and the written version costs almost nothing compared with the alternative.

Flag the pins, because an iron pin nobody can see is not a marker

A practical step that gets skipped and undoes the money spent on the survey. Surveyors set or locate corner monuments, typically iron pins, and those are frequently at or below grade and invisible in grass. Mark them clearly with flags or stakes so that everybody, including the crew and the neighbor, can see the same thing. Photograph them. Then keep the survey, the photographs, the signed contract and any agreement together, because that package is what answers a question in five years, satisfies an inspector who wants the survey on site, and travels with the property when you sell.

A misplaced fence turns up again at closing

The consequence people do not anticipate is that this follows the property rather than the season. Guidance notes that a prospective buyer may request a survey, and that an incorrectly placed fence can complicate or derail a transaction. So a fence built on a guess is not a problem that quietly goes away if the neighbor never mentions it; it is a problem that waits until the least convenient possible moment, when a sale is under contract and there is time pressure on both sides. That is also why the documentation matters as much as the survey itself.