Architecturally exposed steel still has challenges

Innovative techniques for the architectural expression of structural steel have come a long way but there are still many challenges, says University of Waterloo School of Architecture Professor Terri Boake.

At one of the seminars at the recent Construct Canada Show the architect provided an overview of the new Canadian Institute of Steel Construction guide for specifying Architecturally Exposed Structural Steel (AESS) which is intended to help the design and construction professions meet those challenges.

AESS is steel that has been purposefully left exposed but still has to meet the structural requirements, as well as the aesthetic ones, said Boake.

“It usually requires detailing, finish and handling that requires more attention and care than regular structural steel and adds to the cost of the contract.”

Exquisite/expensive detailing needs to be close enough to be seen and even touched to be warranted, said Boake, cautioning that AESS can be priced out of sight on projects if excessive requirements are added “out of ignorance.”

Primary factors which define AESS include mostly bolted or welded connections, close tolerances at both the fabrication and erection stages, and access to detail when performing the required finish. There is some leeway in those definitions, such as when a component of the steel is in a very high location that it is not readily noticeable, said Boake.

The AESS guide is a hierarchal system with categories ranging from one to four, which will appear on architectural, detailing and erection documents. It is expected that AESS 2 for elements viewed at a distance and AESS 3 for elements viewed at a close range (plus or minus six metres) will be the categories most commonly specified, she said.

Even with the guide, some basic rules still apply, said Boake. One of her slides was titled “Keep It Clean. Keep it Durable” and that rule was a major focus of her talk.

“You have to tell the client that durability is an issue,” said the architect, relating the numerous times she’s fulfilled a desire to see a building she long wanted to visit, only to be disappointed.

The audience was shown several slides of high-profile buildings where the steel elements are deteriorating because of pollution, corrosion, damage caused by pigeons, or because they are extremely difficult to clean and maintain because of the design and/or location.

“It (the deterioration) almost makes you want to cry. Steel should be forever.”