What Is a Plat Map?
A plat map is the official recorded document that defines how a piece of land is legally divided. If you've ever wondered exactly where your property line ends, a plat map is the place to look.
The basic definition
A plat map — sometimes called a plat plan or subdivision plat — is a scaled drawing of a parcel of land that has been formally surveyed and recorded with the county. It shows exactly how that land is divided: individual lots, their dimensions, street layouts, easements, rights-of-way, and any other legally significant boundaries.
When a developer builds a new subdivision, they're required to create a plat and have it approved and recorded before they can sell individual lots. That recorded plat becomes the legal description of every lot in that subdivision.
What a plat map shows
Lot numbers and dimensions
Width, depth, and square footage of each lot.
Block numbers
Groups of lots are organized into named blocks.
Street names and widths
Public and private roads, including right-of-way widths.
Easements
Utility corridors, drainage easements, and access strips.
Setback lines
How close structures can be built to lot lines.
Survey data
Bearings, distances, and monument locations.
Subdivision name and phase
The legal name used in all future title documents.
Recording information
Book, page, and date the plat was accepted by the county.
Plat maps vs. other property documents
Plat maps are often confused with other property documents. Here's how they differ:
Plat map vs. deed
A deed transfers ownership of a property and references the lot/block from the plat. The plat defines the boundaries; the deed records who owns them.
Plat map vs. survey
A survey is conducted by a licensed surveyor to locate and mark boundaries in the field. A plat is the recorded document that resulted from a survey — and may be decades old.
Plat map vs. parcel map
A parcel map (or assessor's map) is the county's internal reference for taxation purposes. It's less precise than a plat and not a legal boundary document.
Plat map vs. site plan
A site plan shows what's built on a property (structures, driveways, utilities). A plat shows the legal boundaries of the land itself.
Why plat maps matter
Plat maps come up in nearly every property transaction and dispute:
- ›Buying a home — your title company uses the plat to verify legal boundaries
- ›Building a fence or addition — setback lines on the plat tell you how close you can build
- ›Neighbor disputes — exact lot line locations resolve boundary questions
- ›Understanding utility easements — before digging, know what's crossed your property
- ›Permitting — many permit applications require the plat as supporting documentation
Where to find plat maps
Plat maps are recorded with the county and are public records. Traditionally that meant a trip to the County Recorder's office. PlatMap provides free online access to recorded plat maps for Ada County, Idaho — no subscription required.
Find your plat map
Search by address, subdivision name, or parcel number. Free downloads available.
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