I’m not actually going to review the 2022 New York City Building Code because I don’t want to write that and you don’t want to read that. What I want to do is take a look at some of the significant changes in terms of structural issues and specifically those places that the NYC code deviates from the IBC code that was used as the starting point.
The second disclaimer is that I claim no insider knowledge. Rather, I’m going to provide links to the 2022 and 2014 codes and say what I think about the publicly-available text. Codes always have some ambiguity, which is why building officials in general and the NYC Department of Buildings specifically issue various clarifications – Buildings Bulletins in the case of the NYC DoB – between new editions of codes. So in theory anything I say could be wiped out by a future bulletin.
The third disclaimer is that I’m starting with a topic that is not the focus of my work. A lot of what goes into underpinning is the work of geotechnical engineers, not structural engineers. I’m approaching this topic with regard to structural issues.
Enough preface… Underpinning was addressed by section 1814 of the 2014 code, here. Chapter 18, Soils and Foundations, got longer in the new code, so underpinning is section 1817 of the 2022 code, here.
The first and most obvious change is the length of the section. The 2014 code section is over 400 words, including headings; the 2022 code is almost 3400 words. This is not meaningless blather: a lot of topics are now in the code that were previous not. The one that jumps out at me is, in 2022, section 1817.3 Evaluation of Adjacent Buildings for Suitable Method of Support, which provides detailed instructions for reviewing both the soil and the existing buildings before underpinning. In 2014, this was addressed with two general sentences, but it is now clear what has to be reviewed. There are specific requirements for two common existing conditions with older buildings, rubble-masonry foundations and unreinforced-masonry walls. This was not put in simply to placate people like me, but because underpinning old rowhouses, tenements, and other nineteenth-century masonry buildings has caused a lot of damage over the years.
Other changes include requirements for deep underpinning design, detailed requirements for ordinary (pit-pier) underpinning, and minimum requirements for drawings. What all of the changes have in common is that they are not changes to ordinary practice. Rather, they are codification and explanation of good practice. This is in broad terms what building codes always have been. I don’t have to refer to the New York code section on steel design very often because I’m already doing what that chapter describes. It’s only when dealing with edge cases – peculiar conditions – that I have to look at that chapter. Similarly, I’m sure that the geotechnical engineers who helped write most of section 1817 knew what is in there long before they worked on the section. For someone who does not work with soils every day, this section provides guidance far more than the old section 1814 did.
