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Construction glossary · Steel and structural

What is HSS in construction?

HSS (hollow structural section) is square, rectangular, or round steel tubing, produced to ASTM A500, used in commercial buildings for columns, braces, canopy framing, and handrail posts. A designation like HSS6x6x3/8 gives the outside dimensions and wall thickness, and that size runs about 27.5 lb per ft. Estimators take HSS off the same way as other steel members: linear feet by size, converted to pounds using the weight per foot.

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Updated August 2026 · Reviewed by the Ruh construction team

HSS = hollow structural sectionShapes square, rect, roundCommon in columns & braces

HSS tube wall section

Outer steel wallHollow coreOuter steel wall0.25 in wall6x6 in tube
The definition

HSS (hollow structural section), explained.

HSS shows up all over a commercial steel job: column schedules call out square and rectangular tube columns, brace elevations show diagonal HSS bracing, and the architectural sheets hide more of it in canopy details, stair and handrail details, screen wall framing, and storefront support. The fabricator details it, the erector sets it, and the steel estimator quantifies it alongside wide flange and plate, but it deserves its own line items because it does not price like W shapes. Tube is more expensive per pound, and connecting to a closed shape usually means welded connections, through plates, cap plates, and slotted gussets instead of simple bolted webs. New estimators predictably get burned three ways: pricing HSS at the same per pound rate as the wide flange package, missing the AESS finish premium when the architect exposes the tube and wants ground welds and a paint grade surface, and forgetting the miscellaneous metals scope where HSS hides, such as handrail posts and bollard sleeves that never appear on the structural framing plans. Flag exposed versus concealed HSS in the takeoff from day one.

How it is measured

HSS is taken off in linear feet per size, then converted to pounds using the published weight per foot and rolled up to tons with the rest of the structural steel. Quantities come from the column schedule, framing plans, brace elevations, and the canopy, stair, and railing details on the architectural sheets. Convention is to keep each HSS size as its own line, add a connection allowance for cap plates, base plates, and gussets (often 8 to 12 percent on light tube framing), and round purchase lengths up to mill stock lengths. In the estimate it lands in the structural steel or miscellaneous metals division, with exposed AESS members broken out separately so the finish premium is visible and defensible.

Worked example

A worked HSS (hollow structural section) example.

Worked example

A storefront canopy is framed with 12 HSS6x6x3/8 columns, each 14 ft from baseplate to cap. Step 1, length: 12 x 14 ft = 168 lf. Step 2, weight: HSS6x6x3/8 runs about 27.5 lb per ft, so 168 lf x 27.5 lb/ft = 4,620 lb. Step 3, connection allowance: cap plates, base plates, and gussets typically add about 10 percent on light tube framing, so 4,620 lb x 1.10 = 5,082 lb. Step 4, tons: 5,082 lb / 2,000 = 2.541 tons, carried as 2.54 tons. Step 5, price: at an illustrative fabricated and erected rate of $1.40 per lb, 5,082 lb x $1.40 = $7,114.80, carried as $7,115. If the architect tags these columns as AESS, the finish premium goes on top of that number as its own visible line, never buried inside the base rate.

How Ruh handles it

How Ruh handles HSS (hollow structural section).

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HSS (hollow structural section): frequently asked questions

Why does HSS cost more per pound than wide flange?+

Tube is formed and seam welded from coil rather than hot rolled as an open shape, and fewer mills produce it, so the material itself carries a premium over W shapes. Fabrication adds to the gap: you cannot bolt through a closed section easily, so connections lean on welding, through plates, and cap plates, which means more shop labor per pound. Carry HSS on its own unit rate rather than blending it into the wide flange tonnage.

What does AESS mean for an HSS takeoff?+

AESS is architecturally exposed structural steel: the spec assigns a finish category that can require ground and filled weld seams, eased corners, continuous welds where stitch welds would otherwise do, and a paint grade surface. Exposed HSS at canopies and lobbies is a common AESS target, and the premium over plain shop primer is significant. Take off exposed members as separate line items so the finish cost stays visible.

How do I read a designation like HSS6x6x3/8?+

The first two numbers are the outside dimensions in inches (6 in by 6 in square here) and the last is the nominal wall thickness (3/8 in); round HSS is called out as outside diameter by wall, like HSS6.625x0.280. For takeoff, pull the weight per foot from the AISC tables for that exact designation. The design wall thickness reduction on A500 tube matters to the engineer sizing the member, not to the weight you carry in the estimate.

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Related terms

Steel channelWide flange beamWeld typesBaseplate

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Figures on this page are illustrative. Construction estimates depend on project-specific conditions, source documents, market pricing, and professional judgment. Ruh's AI assists the estimator and does not replace professional review: your team reviews, validates, and approves every estimate, bid, and pricing decision.

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