Steel Angle Uses in Structures: Bracing, Light Trusses, Lintels and an Angle Weight Table

The steel angle is one of the simplest rolled sections, yet it turns up all over a building: as bracing in a steel frame, as members of light roof trusses, and as lintels over doors and windows. This guide walks through the main steel angle uses in structures, the design points that matter for each, and the equal leg angles in the Ahan Asa catalog with their mass per metre, so you can read a size and estimate tonnage before you order.

What a steel angle is and how its size is written

An angle is an L-shaped hot-rolled section, with equal or unequal legs. Their nominal dimensions are set by EN 10056-1; the BSI listing describes the standard as specifying "requirements for the nominal dimensions of hot-rolled equal and unequal leg angles".

An equal angle size is written as leg × leg × thickness in millimetres, so 50×50×5 means two 50 mm legs, 5 mm thick. The equal angles we supply are grade S235JR to EN 10056-1:

To estimate weight, multiply the length by the mass per metre: 12 m of 50×50×5 is about 45.24 kg. Nominal mass is for estimating; delivered weight is what the weighbridge shows.

Angles in bracing

Bracing provides stability and resists lateral loads. Steel Construction Info notes that vertical bracing is usually diagonal members between two lines of columns. A single diagonal must be designed for tension or compression, while crossed diagonals allow slender members that carry tension only.

The "Steel Buildings in Europe" guide to portal frames lists four usual forms of vertical bracing: a single diagonal hollow section, hollow sections in a K pattern, crossed flats considered to act in tension only, and crossed angles. It adds that hollow sections are very efficient in compression, which removes the need for cross bracing; our hollow section buying guide covers that option.

One design point matters on site. An angle is usually connected through one leg, so the load does not pass through its centroid. The Canadian Institute of Steel Construction (CISC) notes that single-angle diagonal braces typically serve as tension-only braces because of their limited compression resistance, and that where one must resist significant compression with only one leg connected it must be designed as an eccentrically loaded column. Take sizes and gusset details from the structural drawings, and do not swap a brace section without the designer's approval.

Angles in light trusses and towers

According to Steel Construction New Zealand's technical note on angle trusses, angle sections are commonly used as members in lightweight triangulated structures such as trusses and towers. Their attraction is ease of fabrication, though they are more complex to design than other structural sections. For column choices in light steel frames, see our comparison of box columns and double I-beams.

Angles as lintels and shelf angles

RMIT University's Build Right guide states that lintels are required wherever brickwork runs over window and door openings, that they are usually angles, flats or T-sections in hot-dip galvanised mild steel, and that they need adequate bearing at each end. Its table gives a 100×100×8 angle with at least 100 mm end bearing for spans over 1 m up to 2.1 m. That is an example from one guide, not a substitute for your designer's calculation.

Brian Trimble's 2009 article in STRUCTURE magazine draws a useful distinction:

• Loose lintels bear on either side of the opening and are not bolted to the structure.
• Shelf angles are bolted to the frame and carry the facing brickwork; leave a gap below them so the angle can deflect or rotate without bearing on the brick below.

Because both sit in damp masonry, corrosion protection matters; our guide to storing steel on site covers care before installation.

Before you order angles

• Copy the full size from the drawings: both leg widths and the thickness.
• Check grade and standard: our angles are S235JR to EN 10056-1.
• Order by kilogram, tonne or metre, and convert lengths to weight with the table above.
• For lintels and external facades, agree corrosion protection with the designer.

Browse all sizes in the angle category, and contact us for a quotation.

Summary

Steel angles have three main structural uses: bracing (especially tension-only cross bracing), members of light trusses and towers, and lintels or shelf angles in masonry. They are easy to fabricate and connect, but they are weaker in compression and the one-leg connection must be allowed for. The designer sets size and detail; the buyer's job is to read the size exactly, estimate weight from the mass per metre, and confirm grade and standard before ordering.