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How to read structural drawings

A beginner's guide to understanding structural engineering plans

Structural drawings show the bones of the building: the columns, beams, slabs, and foundations that hold everything up. Understanding them is essential for coordination, safety, and avoiding costly mistakes. This guide covers the basics.

Step 1: Understand the Sheet Organization

Structural sheets typically follow this order:

S-001
General Notes, Symbols, Abbreviations
S-100 series
Foundation Plans
S-200 series
Framing Plans (floor by floor)
S-300 series
Roof Framing Plans
S-400 series
Sections and Elevations
S-500 series
Details and Schedules

Step 2: Read the General Notes First

The first structural sheet contains critical project-wide information:

  • Design loads (live load, dead load, snow load, seismic criteria)
  • Concrete strength specifications (typically in PSI)
  • Steel grades (A36, A992, etc.)
  • Reinforcing bar grades and cover requirements
  • Foundation bearing capacity assumptions
  • Reference codes and standards

Step 3: Understand the Grid System

The column grid is the reference system for the entire building:

Grid Line Conventions

Letters (A, B, C...): Typically run in one direction (often east-west)

Numbers (1, 2, 3...): Run perpendicular (often north-south)

Grid Intersections: Columns are located at grid intersections (e.g., "Column at B-3")

Intermediate Grids: Use decimals or letters (A.5 or AA) for grids between main lines

Step 4: Read Framing Plans

Framing plans show the structural members at each level:

Beams
Lines with size callouts (W16x40, W21x62)
Columns
Squares or circles at grid intersections
Joists
Parallel lines with joist designation (24K9)
Slab Edges
Heavy lines at perimeter and openings
Openings
Dashed rectangles with "OPENING" note

Step 5: Decode Member Designations

Structural member callouts contain specific information:

Steel Wide Flange: W16x40

W = Wide flange shape

16 = Nominal depth in inches

40 = Weight in pounds per linear foot

Steel Tube: HSS 6x6x1/4

HSS = Hollow Structural Section

6x6 = Width x height in inches

1/4 = Wall thickness in inches

Concrete Beam: 12x24

12 = Width in inches

24 = Depth in inches

Reinforcing shown separately in sections/schedules

Step 6: Find Elevation Information

Structural elevations are critical for coordination:

T.O.S. (Top of Steel)
Top elevation of the steel member
B.O.S. (Bottom of Steel)
Bottom elevation, which is critical for clearances
T.O.C. (Top of Concrete)
Finished concrete surface elevation
B.O.D. (Bottom of Deck)
Underside of metal deck
T.O.F. (Top of Footing)
Top elevation of foundation

Step 7: Use the Schedules

Schedules provide detailed information referenced from plans:

  • Column Schedule: Sizes, reinforcing, and splice locations
  • Beam Schedule: Sizes, reinforcing, camber requirements
  • Footing Schedule: Sizes, reinforcing, bearing elevations
  • Connection Details: Standard connection types referenced by number

Keep exploring

Related references and guides for structural drawing review.

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Structural Plan Symbols Guide

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Structural Abbreviations

Decode abbreviations on structural drawings.

Concrete Mix Design Basics

Understanding concrete specifications on structural plans.

Structural RFI Prevention

Catching structural issues before they become RFIs.

Helonic for Structural Engineers

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Find structural coordination issues fast

Understanding structural drawings is the first step. Finding where they conflict with other disciplines is the next. Helonic's AI automatically identifies coordination issues between structural and MEP drawings.