Structural abbreviations guide
100+ structural engineering abbreviations used on construction drawings, organized by category.
Quick jump
Steel Members & Shapes
W
Wide Flange Beam
WF
Wide Flange
HSS
Hollow Structural Section
TS
Tube Steel
L
Angle (Steel)
C
Channel
MC
Miscellaneous Channel
WT
Structural Tee (cut from W)
MT
Structural Tee (cut from M)
HP
H-Pile (bearing pile)
PL
Plate
BR
Brace
STF
Stiffener
BRG
Bearing
DPH
Diaphragm
Concrete & Masonry
CONC
Concrete
CMU
Concrete Masonry Unit
PC
Precast Concrete
PT
Post-Tensioned
RC
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
EF
Each Face
EW
Each Way
T&B
Top and Bottom
CLR
Clear (cover)
CTR
Center-to-Center
DN
Dowel
SP
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
MP
Micropile
HP
H-Pile
PP
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
EL
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)
SC
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)
FL
Fillet (weld)
BP
Base Plate
AB
Anchor Bolt
Loads & Design
DL
Dead Load
LL
Live Load
SL
Snow Load
WL
Wind Load
EQ
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
FY
Yield Strength
FU
Ultimate Strength
SDC
Seismic Design Category
Wood & Timber
DF
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
PT
Pressure Treated
NOM
Nominal (lumber dimension)
Steel Grade Quick Reference
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.
MG
Manas Gandhi
Co-founder & CTO, HelonicManas 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 · May 2026
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