How to read a site plan
Helonic is an AI construction drawing analysis platform for people reading site plan during plan review.
Understanding property boundaries, grading, utilities, and site features on civil drawings
What is a Site Plan?
A site plan (also called a plot plan) is a bird's-eye view drawing showing the arrangement of improvements on a property. It shows the relationship between buildings, driveways, utilities, landscaping, and property boundaries.
What key elements appear on a site plan?
A site plan shows property boundaries and dimensions, buildings, parking, utilities, and grades so reviewers can see how the project sits on the lot.
- • Property boundaries and dimensions
- • Setback lines (front, side, rear)
- • Easements (utility, drainage, access)
- • Rights-of-way
- • Adjacent property info
- • Building footprint and location
- • Finish floor elevation (FFE)
- • Building entrances
- • Distances to property lines
- • Gross building area
- • Parking areas and counts
- • Driveways and access points
- • Sidewalks and paths
- • Retaining walls
- • Fences and gates
- • Water lines and meters
- • Sewer lines and cleanouts
- • Storm drainage
- • Electrical/gas service
- • Fire hydrant locations
What do contour lines show on a site plan?
Contour lines show elevation changes across the site. Key principles:
The vertical distance between contour lines. Common intervals: 1', 2', or 5'. Smaller intervals show more detail.
Lines close together = steep slope. Lines spread apart = gentle slope or flat area.
Dashed lines = existing contours. Solid lines = proposed (new) contours after grading.
Water flows perpendicular to contour lines. "V" shapes pointing uphill indicate valleys/swales.
What are spot elevations and benchmarks on a site plan?
Specific elevation points are called out on site plans:
| Abbreviation | Meaning | Usage |
|---|---|---|
| FFE | Finish Floor Elevation | Building entry levels |
| TW | Top of Wall | Retaining walls |
| BW | Bottom of Wall | Retaining walls |
| TC | Top of Curb | Curb and gutter |
| FL | Flow Line | Drainage channels |
| INV | Invert | Pipe bottom elevation |
| BM | Benchmark | Survey reference point |
What symbols appear on a site plan?
Site plans use a north arrow, existing-tree symbols, and similar survey marks that the civil legend defines.
Symbols vary between firms and municipalities. Always reference the legend on Sheet C-001 or the symbol key.
What do setback lines show on a site plan?
Setback lines show minimum distances from property lines where building is not permitted:
- Front setback, Distance from street/right-of-way
- Side setback, Distance from side property lines
- Rear setback, Distance from rear property line
- Corner lot, May have two front setbacks
Setbacks are determined by local zoning ordinances and vary by zoning district. Building footprint must stay within the "buildable area" defined by setback lines.
Keep exploring
Related references and guides for site and civil drawing review.
Utilities, drainage, and grading symbols
Understanding engineering scales
Common abbreviations on site plans
Complete guide to building drawings
Drainage design, BMPs, and erosion control
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