Hollow Structural Sections (HSS) are the second most common structural steel section after wide flange beams. They appear in columns, bracing, trusses, canopies, handrails, and secondary framing on almost every structural steel project. Here's the complete reference for estimators.
What Is an HSS Section?
HSS (Hollow Structural Section) is the North American term for structural hollow sections — rectangular, square, and round steel tubing produced to ASTM A500 (Grade B or C is most common) or A1085. The material is stronger per unit weight than older pipe standards and is purpose-designed for structural applications.
In the UK and Australia, equivalent sections are called SHS (Square Hollow Section), RHS (Rectangular Hollow Section), and CHS (Circular Hollow Section). The dimensions are similar but not identical and the sections are governed by different standards.
How to Read an HSS Designation
Rectangular HSS
Format: HSS[height]x[width]x[wall thickness]
All dimensions in inches (US) or mm (metric).
- HSS8x6x1/4 — 8 inches tall, 6 inches wide, 1/4 inch (0.250") wall thickness
- HSS12x4x3/8 — 12 inches tall, 4 inches wide, 3/8 inch wall
- HSS6x4x1/4 — 6 inches tall, 4 inches wide, 1/4 inch wall
The height dimension is typically the dimension in the structural loading direction (depth in bending).
Square HSS
Format: HSS[size]x[size]x[wall thickness]
- HSS6x6x1/4 — 6 inches square, 1/4 inch wall
- HSS10x10x1/2 — 10 inches square, 1/2 inch wall
- HSS4x4x3/16 — 4 inches square, 3/16 inch wall
Square HSS is very common for columns, bracing, and truss members.
Round HSS
Format: HSS[outside diameter]x[wall thickness]
- HSS6.000x0.250 — 6-inch OD, 1/4-inch wall
- HSS10.000x0.375 — 10-inch OD, 3/8-inch wall
- HSS3.500x0.216 — 3.5-inch OD, 0.216-inch wall
Note that round HSS outside diameter designations use decimal inches. This distinguishes them from pipe, which uses nominal pipe size (NPS) designations (a 6" pipe has an actual OD of 6.625").
Common HSS Sizes and Weights
Rectangular HSS — Frequently Used in Structural Work
| Designation | Weight (lb/ft) | Typical Use | |---|---|---| | HSS4x2x3/16 | 5.41 | Light bracing, secondary | | HSS6x4x1/4 | 11.35 | Bracing, secondary framing | | HSS8x4x5/16 | 16.96 | Bracing, canopy framing | | HSS10x6x3/8 | 29.23 | Heavy bracing, light beams | | HSS12x6x1/2 | 45.61 | Transfer beams, crane support | | HSS14x10x5/8 | 76.07 | Heavy columns, specialty |
Square HSS — Frequently Used for Columns and Bracing
| Designation | Weight (lb/ft) | Typical Use | |---|---|---| | HSS4x4x3/16 | 8.15 | Light column, bracing | | HSS5x5x1/4 | 12.21 | Mezzanine column | | HSS6x6x1/4 | 14.72 | Standard column | | HSS6x6x3/8 | 21.63 | Heavier column | | HSS8x8x5/16 | 26.41 | Industrial column | | HSS10x10x1/2 | 54.48 | Heavy column | | HSS12x12x1/2 | 65.87 | Major column | | HSS14x14x5/8 | 100.27 | Very heavy column |
Round HSS — Common Sizes
| Designation | Weight (lb/ft) | Typical Use | |---|---|---| | HSS3.500x0.216 | 7.58 | Railing posts, light secondary | | HSS4.500x0.237 | 10.79 | Railing, light column | | HSS6.000x0.250 | 15.58 | Column, brace | | HSS8.000x0.322 | 27.48 | Column | | HSS10.000x0.365 | 38.74 | Heavy column | | HSS12.000x0.375 | 47.90 | Major column |
Wall Thickness Designations: Fractions vs. Decimals
AISC uses fractional wall thickness designations (1/4", 5/16", 3/8", 1/2", 5/8") for rectangular and square HSS. Structural drawings may use either fractions or decimals. Common equivalences:
| Fraction | Decimal | Actual wall (design) | |---|---|---| | 3/16 | 0.188 | 0.174" (ASTM A500) | | 1/4 | 0.250 | 0.233" | | 5/16 | 0.313 | 0.291" | | 3/8 | 0.375 | 0.349" | | 1/2 | 0.500 | 0.465" | | 5/8 | 0.625 | 0.581" |
Note that ASTM A500 allows the actual wall thickness to be up to 10% less than the nominal. The AISC section database uses design wall thickness (about 93% of nominal) for section property calculations. This matters for weight calculations — the AISC tabulated weight already accounts for the A500 tolerance.
HSS Estimating: Weight Calculation
Like W shapes, HSS weight calculation is straightforward:
Piece weight = weight per foot × length in feet
For HSS6x6x1/4 at 18 feet: 14.72 lb/ft × 18 ft = 264.96 lb = 0.132 tons.
The weight per foot values come from the AISC section database (available in the Steel Construction Manual or online). Don't calculate from the nominal wall dimensions — use the tabulated weight which accounts for the design wall thickness.
How HSS Appears on Structural Drawings
HSS sections are labeled with their full designation on structural drawings: HSS6x6x1/4, HSS8x4x5/16, HSS6.000x0.250. Some older drawings use "TS" (Tube Steel) prefix instead of HSS — TS6x6x1/4 is the same as HSS6x6x1/4 for estimating purposes. Metric drawings label sections in mm: HSS152x152x6.4 (equivalent to HSS6x6x1/4 in imperial).
Some drawings use "pipe" designations for round sections. Know the difference: 6" Std. pipe (6.625" OD, 0.280" wall, 18.97 lb/ft) is different from HSS6.000x0.280. The structural engineer should specify which — if you're unsure, ask. For understanding steel drawing labels and abbreviations, that reference guide covers the full range of markings.
HSS vs. W-Shape: When Each Is Used
HSS sections have advantages and disadvantages compared to W shapes:
HSS advantages:
- Efficient in compression (torsion-resistant, no torsional buckling)
- Architecturally clean (no protruding flanges)
- Good for diagonal bracing where loading is axial
- Visually preferred for exposed structural applications
W-shape advantages:
- More efficient in bending (more material farther from neutral axis)
- Easier to connect (flanges and webs are accessible)
- Wider range of section sizes and weights
- Generally lower cost per ton for heavy sections
In practice: W shapes dominate for beams and girders; HSS dominates for columns, bracing, trusses, and exposed architectural steel.
Common HSS Estimating Mistakes
Confusing HSS with pipe. They are different products with different designations and properties. HSS round and structural pipe look similar but have different ODs at the same nominal size.
Missing brace connections. HSS bracing in X-patterns requires gusset plates at each end and at the intersection. These are often significant connection elements — sometimes heavier than the bracing itself.
Assuming standard availability. Very large HSS sections (HSS14x14x5/8, HSS16x16+) are not standard stock items at most service centers. Longer lead times and higher prices apply.
Using nominal wall thickness for weight. Always use the AISC tabulated weight, which accounts for the A500 wall tolerance. Calculating your own weight from nominal dimensions overestimates weight by approximately 7%.
For a comprehensive extraction approach including HSS and all other section types, see the steel takeoff overview. Tools like SteelFlo identify and cross-reference HSS designations across all formats (HSS, TS, pipe, metric equivalents) in the section database automatically.
Frequently Asked Questions
What is the difference between HSS and tube steel?
They are the same product. "Tube steel" (TS) is an older designation. The current AISC standard uses HSS (Hollow Structural Section). If you see TS6x6x1/4 on an older drawing, it's equivalent to HSS6x6x1/4.
What ASTM standard covers HSS for structural use?
ASTM A500 (Grade B or C) is the most common specification for cold-formed HSS in North America. ASTM A1085 is a newer, higher-quality specification with tighter tolerances and a defined minimum yield. Some designers specify A1085 for applications where the A500 wall tolerance is a concern. A500 Grade B has a 46 ksi minimum yield; A500 Grade C has 50 ksi; A1085 has 50 ksi with tighter tolerances.
How do I tell if a section on a drawing is HSS square or HSS rectangular?
If the first two dimensions are equal (HSS6x6x1/4), it's square HSS. If the dimensions differ (HSS8x6x1/4), it's rectangular HSS. On drawings, both types use the same designation format — the size values tell you which you're looking at.
What does the weight per foot for HSS steel depend on?
Weight per foot depends on outside dimensions and design wall thickness. The AISC tabulated weights use design wall thickness (about 93% of nominal for ASTM A500). Larger sections with thicker walls weigh more per foot. The exact values are in the AISC Steel Construction Manual HSS section property tables.
Are HSS and SHS/RHS/CHS the same thing?
They describe the same shape types but are governed by different standards. HSS is the North American designation (ASTM A500/A1085). SHS, RHS, and CHS are the European and Australian terminology (EN 10219, AS/NZS 1163). Dimensions are similar but properties are defined differently, and they're not interchangeable on specification-sensitive work. For international projects, always verify the applicable standard.