October 6, 2026  ·  Excavation services

How to Read a Site Plan Before You Dig

Blog  /  How to Read a Site Plan Before You Dig

A site plan is a contract written in lines and numbers. Most homeowners glance at it, recognize the rectangle that's going to be their house, and trust the rest. Then six months later they find out the deck setback they didn't see on the drawing is the reason the inspector won't sign off. Reading the plan is a 20-minute skill that pays back every time.

This is what to look for before you let an excavator start on a lot in Ringgold, Hixson, or anywhere else in the region.

The five things every site plan shows

  1. Property boundaries — the legal lot lines with bearings and distances.
  2. Setbacks — the minimum distances from each boundary that you can build inside.
  3. Existing conditions — current contours, trees, structures, utilities.
  4. Proposed work — the new footprint, driveway, septic/sewer, drainage features.
  5. Elevations and contours — the topography, expressed as numbered lines.

If any of those five are missing, the plan isn't done. Don't dig from a plan that doesn't have all five.

Reading contour lines

Contour lines are the squiggly lines with numbers. Each line represents a single elevation — every point on that line is at that height above sea level (or a local benchmark). On most residential plans, contours are drawn every 1 or 2 feet of vertical change.

Three things to notice:

  • Spacing. Lines packed close together mean steep terrain. Lines far apart mean flat. A wall of stacked contours on a hillside in Lookout Mountain tells you the lot drops fast — and that you're going to either cut hard, build retaining walls, or use a stepped foundation.
  • Direction of fall. Water flows perpendicular to contour lines, downhill. Trace it from the high point of the lot to where it leaves the property. That's where your drainage problem either exists or doesn't.
  • Spot elevations. Dots with numbers next to them. These are exact elevations called out at key points — corners of the house, driveway grades, finished floor.

Setbacks — the lines you can't cross

Every jurisdiction has minimum distances from property lines. Front, side, and rear setbacks are usually different numbers. Look for dashed lines parallel to the property lines, often labeled with feet. The buildable area is what's left in the middle.

Easements are different. An easement is a strip across your lot where someone else has rights — utility company, neighbor, drainage flow. You can usually still landscape it, but you generally can't build over it. Watch for "10' utility easement" or "20' drainage easement" notes.

Existing utilities

Look for:

  • Underground electric (often labeled "UGE")
  • Gas lines ("G")
  • Water and sewer ("W" and "S")
  • Communications and cable ("C")
  • Septic tank and drain field (separate symbols, often hatched)

If your plan shows utilities, that's helpful but not enough. You still need to call 811 for a fresh locate — site plans aren't always accurate, and lines move over time. We cover that in detail in why utility locates matter.

Existing and proposed grades

Two contour sets often overlay each other:

  • Existing contours — typically drawn as light or dashed lines.
  • Proposed contours — drawn solid, sometimes in a different color.

Where they diverge, dirt is going to move. Existing line at elevation 712 turning into a proposed line at 716 means 4 feet of fill in that spot. Existing at 720 going to proposed at 715 means 5 feet of cut. This is how you read cut and fill volume directly off the plan.

The legend and notes

Don't skip the legend in the corner. It explains symbols you'd otherwise guess at — trees to remove, trees to save, retaining wall lines, swale arrows, silt fence routes.

Read the notes block too. It often contains the critical sentences: "Contractor to verify elevations in field," "Erosion control per local stormwater rules," "Maintain 6 inches fall in 10 feet from foundation."

Red flags worth a conversation before you dig

  • Finished floor elevation lower than the road. Water moves toward you, not away. Verify drainage.
  • Driveway grade steeper than 12–15%. Hard on cars, hard to plow, sometimes against local code.
  • Proposed grade against a property line. You can't dump water onto a neighbor's lot.
  • Building footprint right next to a setback line. Any field adjustment puts you in violation.
  • No drainage features shown. Means none were planned. Means you'll be planning them in the field.

What to bring to the pre-dig walk

When we walk a site with a homeowner or builder, the conversation goes faster if you bring:

  • A printed site plan (not just on a phone screen)
  • A tape measure
  • The 811 locate ticket and any mark-outs already on the ground
  • A list of trees to preserve
  • The grading and drainage notes from the plan

A clear 30-minute walk catches things that would cost days to fix later. For complex builds, the same conversation belongs in your building pad and footings planning.

FAQ

Do I need a site plan for a small project?

For a single driveway extension or a shed pad, sometimes a sketch is enough. For anything that needs a permit — house, addition, pool, large structure — a site plan is usually required.

Who draws the site plan?

Typically a surveyor or civil engineer. Some builders draw their own for permitting. Architects produce them for the building itself.

Can the excavator change the plan in the field?

Small adjustments, yes — to dodge a rock shelf, save a tree, or improve drainage. Changes that move building footprint or grades should go back to the designer.

What does "benchmark" mean on a plan?

A reference elevation everyone agrees on — often a survey monument, a manhole rim, or a marked stake. All other elevations are measured relative to it.

Ready to break ground?

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