In September of 2011, Anton Nelson of the New York-based engineering firm Dewhurst Macfarlane and Partners PC wrote the attached specification for AESS (Architecturally Exposed Structural Steel). The purpose of creating this new spec was to close some of the loopholes in the AISC-based spec that had been exploited by unscrupulous subcontractors.

Possibly in response to the current economic climate, fabricators had used these loopholes to claim that obviously substandard work met the technical requirements of the AISC spec, even though it was not visually appealing. During the rewriting process, Mr. Nelson consulted with Julian Bowron of Vector Praxis. The collaboration resulted in the inclusion of text which borders on “instructional”, specifically with regard to selection and handling of material, welding procedures and other practical techniques for the production of AESS. Please note that these techniques are routinely implemented by high quality fabricators, but they do add cost, so they are the first thing to go if a fabricator is financially stressed.

The “DewMac” spec includes some interesting features. Two that stand out are as follows:

1) The AESS spec incorporates parts of the sample CISC (Canadian Institute of Steel Construction) spec for AESS which was developed in 2007 by a committee of the CISC (chaired by Walter Koppelaar, President of the Walters Group and co-owner of Feature Walters). The most prominent feature is the matrix which creates 5 categories of AESS work based on viewing distance, while allowing for the addition of even more stringent criteria in high-profile areas.

2) In keeping with the “instructional” model of specification, visual inspection techniques are described which are designed to reveal irregularities in the plant before they become apparent in the field.

This article is presented in the form of a downloadable annotated version of the DEWMAC AESS spec and is directed to engineers, architects and contractors who need to understand the cost and / or supervisory implications of the spec. The annotations are highlighted in yellow in the downloadable document (below).