In the context of construction, “AESS” stands for “Architecturally Exposed Structural Steel.” AESS refers to structural steel elements that are intentionally left visible and exposed in a building or structure, rather than being hidden behind finishes or cladding. This includes steel columns, beams, trusses, and other components that contribute to the structural integrity of the building.
Architecturally Exposed Structural Steel is often used in architectural designs to create an aesthetically pleasing and visually distinctive appearance. It allows the structural steel to become an integral part of the building’s design, showcasing its strength and beauty. AESS elements are typically fabricated and finished with special care to achieve a desired architectural finish, which may involve techniques such as sandblasting, painting, or even applying a specific texture or patina.
Recommended for you: Surface preparation for structural steel.
The use of AESS can be seen in various types of buildings, such as bridges, stadiums, museums, and high-rise structures. It requires close collaboration between architects and structural engineers to ensure that the exposed steel elements meet both structural requirements and the desired aesthetic vision for the building.
What are the categories of AESS?
Both AISC and CISC developed definitions to establish different AESS categories for the steel based on the viewing distance, type/function of the structure, and cost increase to achieve sequentially higher AESS categories:
AESS 1: Basic elements
This level represents the simplest and least visually demanding appearance for exposed structural steel. It typically involves minimal surface preparation and edges ground smooth. Welds and other connections may be visible, but they are not required to have a high-quality finish.
 |
| AESS 1: Ricoh Coliseum in Toronto |
AESS 2: Feature elements viewed at a distance greater than 20 ft (6 m)
At this level, there is an increased emphasis on the appearance of the exposed steel elements. The surface preparation and fabrication techniques are improved, resulting in a more refined finish. Welds uniform or ground smooth, fabrication marks disappeared and there is greater attention to detail in achieving a consistent appearance.
 |
| AESS 2: Skylight in Les Ailes (Montréal) |
AESS 3: Feature elements viewed at a distance less than 20 ft (6 m)
AESS 3 requires a high level of craftsmanship and attention to detail. It involves extensive surface preparation, which may include grinding, blending, or polishing of welds and connections. Mill marks are removed, and joint gap tolerance minimized. The steel elements are expected to have a smooth and refined appearance, with minimal visible imperfections.
 |
| AESS 3: Ottawa International Airport |
AESS 4: Showcase elements with special surface and edge treatment beyond fabrication
This is the highest level of AESS and demands the most exacting standards for appearance. AESS 4 requires exceptional craftsmanship and precision. The surfaces filled and sanded, HSS seams disappear, weld contoured and blended resulting in a near-perfect finish. The steel elements are expected to have an exceptional aesthetic appeal, with virtually no visible imperfections.
 |
| AESS 4: Brookfield Place in Toronto |
AESS C: Custom elements with characteristics described in the contract document
The last category is about creating custom structures where there doesn’t need to be smooth at the close view or can have sharp edges on other spaces; it allows for more flexibility than different categories.
Also read: What is galvanization and what are galvanizing methods.
What is the difference between AESS and regular steel?
Unlike regular structural steel, AESS is crafted to achieve both a structural purpose and an aesthetic one. To achieve a look that will last for generations, all debris, oil, and grease must be removed, and all welds must be ground smooth.
Can AESS steel be galvanized?
 |
| Harley Davidson Museum in Wisconsin |
The Harley Davidson Museum in Wisconsin is a great example of hot-dip galvanized steel used in an AESS design. More and more, specifiers are looking to hot-dip galvanize Architecturally Exposed Structural Steel (AESS) to create artful, durable, and sustainable structures for generations to enjoy.