Exploring Architecturally Exposed Structural Steel

May 30, 2024

Custom Metal Canopies with Lights

Structural steel finishing is a vital surface treatment technique that transforms the properties of steel structures, enhancing both their functionality and aesthetics.

This step in the fabrication process prepares the steel for various applications, ensuring optimal performance and appearance.

Expert assistance offered by Feature Walters can greatly aid in identifying the optimal finish for a particular application. Let’s look into the diverse types of Architecturally Exposed Structural Steel (AESS) finishes we offer.

What is Architecturally Exposed Structural Steel?

Shelter Canopies made of AESS

AESS, or Architecturally Exposed Structural Steel, is designed to meet both structural and aesthetic requirements as it remains visible.

Architecturally Exposed Structural Steel (AESS) is a type of structural steel that’s designed and finished to be aesthetically pleasing because it’s intended to be visible in the finished construction of a building.

Unlike standard structural steel elements, which are typically hidden behind walls or other materials, AESS is left exposed and often serves as a prominent architectural feature.

An architect might opt to use AESS in more modern designs, including in commercial buildings, bridges, airports, and other structures where the steel elements are intended to be a visible and integral part of the architectural aesthetic.

Given its visibility, AESS demands meticulous detailing and finishes, surpassing conventional structural steel hidden behind other materials.

Incorporating AESS into steel design requires careful consideration to achieve a balance of form, symmetry, and cost-effectiveness, alongside structural integrity and performance. AESS is categorized into different levels, each representing varying degrees of finish and detailing.

AESS in Action ↓

Feature Walters fabricated and installed VivaNext canopy bus shelters for the York Region of Ontario.

The canopies began as three separate nine-metre pieces of high-level AESS finish joined seamlessly together. They were then coated in automative grade external paint to minimize maintenance costs.

AESS Categories

The AESS category systems are based on the level of finish, detailing, and visual quality required. The categorization helps guide the design, fabrication, and erection processes to ensure the desired aesthetic and functional outcomes.


  • This form of AESS is used for basic elements and achieves high fabrication tolerances.
  • It should be utilized for elements with a viewing distance greater than 20 metres away.
  • There is a lower to moderate cost premium over standard structural steel.
  • AESS 1 does not focus on or affect the surface finishing of elements, but rather fabrication and connection tolerances.
  • Any weld splatter is removed.

AESS 2 & 3

  • This form of AESS is used for high-end ornamental elements and has a moderate cost premium.
  • It should be utilized for elements that have a 10-to-20-meter viewing distance.
  • AESS 2 & 3 do not focus on or affect the surface finishing of elements, but rather fabrication and connection tolerances.
  • Welds are smooth.

What is the difference between AESS 2 and AESS 3?

AESS 2 and AESS 3 differ primarily in the level of finish and detail required.

AESS 2 is suitable for elements viewed from 20 feet or more, where minor surface imperfections are acceptable, and the finish is moderately smooth.

Welds are generally smooth but may have minor flaws, and standard fabrication tolerances apply, with visible but treated connections to ensure a decent overall appearance.

In contrast, AESS 3 is intended for elements viewed up close, within 20 feet, demanding a higher quality finish with no surface imperfections. Welds in AESS 3 are ground smooth and continuous, requiring extensive grinding and polishing.

Tighter fabrication and erection tolerances are necessary, and connections are meticulously detailed to minimize visual impact, often concealing bolts or treating them to blend seamlessly with the surrounding steel.


  • This form of AESS focuses on the surface of the steel.
  • Welds are ground smooth, with no blemish on the surface.
  • AESS 4 is often referred to as an automotive finish.

AESS in Action ↓

These AESS steel canopies were designed to be a horizontal extension of the undulating curtainwall of the iconic Manhattan high-rise, One 57.

The constantly curving geometry of the curtainwall transitions into our scope of steel structure, stainless cladding and glass soffits.

How Amazing is AESS!

Custom Metal Canopies with Lights

Offering a wide array of possibilities, architecturally exposed steel elevates steel structures to new heights of elegance and durability.

It’s suitable for a variety of projects, from feature stairs to unique metal work, seamlessly blends aesthetics with functionality, and offers a finish that can withstand both time and weather.

At Feature Walters, we pride ourselves on our ability to guide clients in selecting the ideal finish for their projects. With our commitment to detail and innovative solutions, we ensure that everything we build stands out in both form and function. Partner with us, and let’s bring your architectural visions to life with AESS.

Stay tuned for our upcoming post on brush finishes as we continue to explore steel finishes!

The Feature Walters Design Guide


Our Feature Walters team has created this guide as a resource to help educate and inspire you with the many styles, materials and finishes available for architects seeking leading-edge architectural options for feature staircases.

"*" indicates required fields

This field is for validation purposes and should be left unchanged.

Browse News by Category