What is a base sheet?
A base sheet (also called a base plan or existing-conditions plan) is the drawing that shows what's on and around a site before design starts: property lines, topography, buildings, roads, utilities, vegetation and regulated areas such as floodplain and wetlands. Every design sheet (layout, grading, planting, irrigation) references it, usually as an Xref in CAD. It comes either from a survey or, for early planning, from public GIS data.
What's on it
- Property lines, easements and rights-of-way
- Topography: contours and spot elevations
- Existing structures, paving, walls and fences
- Roads, curbs and driveways
- Utilities (from the survey and locates)
- Trees and vegetation
- Regulated areas: floodplain, wetlands and buffers, steep slopes
- North arrow, scale, sources and date
Survey base vs GIS base
A surveyed base is the legal and dimensional record you build construction documents on. A GIS base, assembled from public parcel, LiDAR, soils, flood and wetland data, is faster and free, and is what most offices use for feasibility, proposals and concept design before a survey is ordered. See base plan vs survey.
How offices use it
- Kept in one CAD file and referenced into every design sheet, so updates flow through.
- Layered to an office standard or the US National CAD Standard, so linework prints and turns off predictably.
- Drawn in real-world coordinates (State Plane) so it lines up with civil and survey files later.
Everything here is planning-level public data. Confirm boundaries, topography, wetlands and flood status with a licensed surveyor and the right specialists before design decisions depend on them.
Basesheet does all of this for any US address in about 30 seconds, free, with no account.
Build a base planRelated
- How to make a site base plan from an address
- Public-data base plan vs a boundary survey
- How to get a parcel boundary into AutoCAD or Civil 3D
Updated October 2026.