Structural abbreviations guide

Helonic is an AI construction drawing analysis platform for teams researching structural abbreviations during drawing review.

100+ structural engineering abbreviations used on construction drawings, organized by category.

Quick jump

Steel Members & Shapes Concrete & Masonry Reinforcing Foundations Elevations & Dimensions Connections & Welding Loads & Design Wood & Timber

Steel Members & Shapes

Wide Flange Beam

Wide Flange

HSS

Hollow Structural Section

Tube Steel

Angle (Steel)

Channel

Miscellaneous Channel

Structural Tee (cut from W)

Structural Tee (cut from M)

H-Pile (bearing pile)

Plate

Brace

STF

Stiffener

BRG

Bearing

DPH

Diaphragm

Concrete & Masonry

CONC

Concrete

CMU

Concrete Masonry Unit

Precast Concrete

Post-Tensioned

Reinforced Concrete

CIP

Cast-in-Place

SOG

Slab on Grade

SOD

Slab on Deck

FRC

Fiber Reinforced Concrete

GRT

Grout

LWC

Lightweight Concrete

NWC

Normal Weight Concrete

PSI

Pounds per Square Inch (strength)

FC'

Concrete Compressive Strength

Reinforcing

Rebar Bar Size Number

REINF

Reinforcing

Each Face

Each Way

T&B

Top and Bottom

CLR

Clear (cover)

CTR

Center-to-Center

Dowel

Splice

LAP

Lap Splice

STR

Stirrup

TIE

Tie (column)

WWF

Welded Wire Fabric

WWR

Welded Wire Reinforcement

GR 60

Grade 60 Rebar (60 ksi yield)

GR 40

Grade 40 Rebar (40 ksi yield)

Foundations

FTG

Footing

GRD BM

Grade Beam

PIR

Pier

CAP

Pile Cap

Micropile

H-Pile

Pipe Pile

DRL

Drilled Shaft/Pier

MAT

Mat Foundation

FFE

Finish Floor Elevation

B.O.F.

Bottom of Footing

T.O.F.

Top of Footing

BRG

Bearing (soil capacity)

Elevations & Dimensions

Elevation

T.O.S.

Top of Steel

B.O.S.

Bottom of Steel

T.O.C.

Top of Concrete

T.O.W.

Top of Wall

B.O.D.

Bottom of Deck

T.O.D.

Top of Deck

T.O.P.

Top of Parapet

FIN FLR

Finish Floor

SFL

Structural Floor Level

CLR HT

Clear Height

AFF

Above Finish Floor

BFF

Below Finish Floor

Connections & Welding

BLT

Bolt

HSB

High-Strength Bolt

A325

ASTM A325 Bolt (bearing type)

A490

ASTM A490 Bolt (high strength)

Slip-Critical (connection)

STD

Standard (hole)

OVS

Oversized (hole)

SSL

Short Slotted (hole)

LSL

Long Slotted (hole)

CJP

Complete Joint Penetration (weld)

PJP

Partial Joint Penetration (weld)

Fillet (weld)

Base Plate

Anchor Bolt

Loads & Design

Dead Load

Live Load

Snow Load

Wind Load

Earthquake (seismic)

PSF

Pounds per Square Foot

PLF

Pounds per Linear Foot

KSF

Kips per Square Foot

KLF

Kips per Linear Foot

KIP

1,000 Pounds

KSI

Kips per Square Inch

Yield Strength

Ultimate Strength

SDC

Seismic Design Category

Wood & Timber

Douglas Fir

SPF

Spruce-Pine-Fir

SYP

Southern Yellow Pine

GLB

Glue-Laminated Beam (Glulam)

LVL

Laminated Veneer Lumber

PSL

Parallel Strand Lumber

LSL

Laminated Strand Lumber

TJI

Engineered Wood I-Joist

PLY

Plywood

OSB

Oriented Strand Board

Pressure Treated

NOM

Nominal (lumber dimension)

What steel grades appear most often on drawings?

Most structural drawings use A36, A992, and A500 grades, and the grade must match the general notes.

A36Fy = 36 ksi

General structural steel, plates, angles, channels

A572 Gr 50Fy = 50 ksi

Higher strength structural shapes and plates

A992Fy = 50 ksi

Standard for W-shapes (wide flange beams)

A500 Gr BFy = 46 ksi

Cold-formed HSS (tube steel)

A500 Gr CFy = 50 ksi

Cold-formed HSS (higher strength)

A53 Gr BFy = 35 ksi

Pipe (standard weight)

A325Fy = 92 ksi min

High-strength bolts (bearing type)

A490Fy = 130 ksi min

High-strength bolts (higher capacity)

Practitioner insight

“The structural abbreviations that get misread most often are not the dramatic ones, it's the small stuff. TOS vs. TOC on a podium-to-tower interface, or CLR vs. COVER vs. the actual rebar size. We've seen 1-1/2 inch cover specs misread as bar size and built that way. The fix is always reading the abbreviation against the project's general-notes legend, not what you remember from another job.”

Conversations with structural EORs, structural shop drawing reviewers, and VDC engineers working on cast-in-place and post-tensioned concrete projects.

Frequently Asked Questions

What are the most common structural abbreviations on construction drawings?

The most frequently used structural abbreviations are BM (beam), COL (column), FTG (footing), CONC (concrete), REINF (reinforcement), CLR (clear cover), EL (elevation), TYP (typical), TOS (top of steel), TOC (top of concrete), CIP (cast-in-place), CMU (concrete masonry unit), and SOG (slab on grade). On steel projects, AISC member callouts like W14x68 (wide flange), HSS6x6x1/4 (hollow structural section), and L4x4x3/8 (angle) function as both designation and abbreviation.

What does CLR or COVER mean in structural drawings?

CLR (clear cover) is the distance from the outside face of concrete to the nearest face of reinforcing bar. It's a critical structural specification governed by ACI 318, typical values are 3/4 inch for slabs not exposed to earth or weather, 1-1/2 inch for beams and columns, 2 inches for concrete exposed to earth, and 3 inches for concrete cast against earth. Insufficient cover compromises fire rating, corrosion protection, and bond strength.

What does TOS, TOC, BOS mean?

TOS (top of steel) is the finished top elevation of structural steel framing, used to dimension where decking lands. TOC (top of concrete) is the finished top elevation of a concrete slab or footing. BOS (bottom of steel or bottom of slab, context-dependent) is the bottom elevation. These appear next to elevation marks on framing plans and sections, for example 'TOS EL +12'-0"' means the top of steel at that point is at elevation +12 feet.

What are AISC steel section abbreviations?

AISC (American Institute of Steel Construction) defines standard section designations: W = wide flange (e.g., W14x68 means 14 inches deep, 68 pounds per foot), HSS = hollow structural section (HSS6x6x1/4 = 6" square tube, 1/4" wall thickness), L = angle (L4x4x3/8 = 4" leg, 4" leg, 3/8" thickness), C = channel (C12x20.7), MC = miscellaneous channel, S = American Standard beam, WT = T-section cut from a W shape, and PL = plate (PL 1/2 = 1/2 inch plate). The full reference is the AISC Steel Construction Manual.

What is the difference between CIP, P/T, and PC concrete?

CIP (cast-in-place) is concrete poured in formwork on-site. P/T or PT (post-tensioned) is concrete that has high-strength steel cables tensioned after the concrete cures, used for thinner long-span slabs and beams. PC (precast) is concrete manufactured off-site and erected, often pre-tensioned (PT cables tensioned before concrete pour). The abbreviation tells you where the structural element was made and how it carries load, three very different shop-drawing review processes.

Where can I find the abbreviation legend for a specific project?

Every structural drawing set has an abbreviation legend on the general-notes sheet, typically S0.0, S0.1, or S001. That legend is the authoritative list for the project, abbreviations vary slightly between firms and structural disciplines (concrete EORs and steel EORs sometimes use different conventions). On large projects with multiple structural consultants (e.g., podium + tower), each consultant's section may have its own legend.

Manas Gandhi

Co-founder & CTO, Helonic

Manas is the co-founder and CTO of Helonic, where he leads engineering and AI research for construction drawing analysis. He works directly with structural, MEP, civil, and fire protection engineers to translate the way they review drawings into AI systems that flag the issues that actually matter in the field. Before Helonic, he built machine learning pipelines for technical document understanding and has spent the last several years interviewing licensed design engineers and discipline leads to ground product decisions in real practice rather than industry assumptions.

Areas of focus

AI for technical document understanding
Cross-discipline coordination workflows
Code compliance automation (IBC, NEC, NFPA, IPC, IMC, ASCE)
Structural and MEP drawing review systems

Last reviewed by Manas Gandhi · August 8, 2026

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