You can Rock on the Roof but No Rocks Please
By Austin Regan
Some building owners are fortunate enough to have buildings located in the correct zoning and community board districts, and had enough foresight to have their buildings designed to accommodate a rooftop bar or party space.
Those buildings may have revelers dancing on the roof to Hip-Hop and Rock, but, if it is a 2014 Code building, that roof will have no rocks. Starting with the 2014 Code, gravel or stone ballast or roof coverings will not be allowed. BC 1504.8 bans aggregate from being used in “hurricane prone regions. Per BC 1609.2 the definition of a hurricane prone region states “New York City is within the hurricane-prone region.”
This new restriction is a result of changes to the Code spurred by the aftermath of Hurricane Sandy. While many parts of the Code were affected, Chapter 16 – Structures – has seen some major revisions. Many of these changes have to do with designing for wind loads.
Starting with BC 1609.4, the relevant exposure categories have changed. The least restrictive category – Exposure A – no longer applies to any part of the five boroughs. Category D, which was not in the 2008 Code, now applies to certain areas like Jamaica Bay.
New factors are taken into account to determine these categories. Wind directions and sector (BC 1609.4.1) now must be evaluated based on the predominant wind direction plus 45% in either direction. Surface roughness categories (BC 1609.4.2) taking into account surrounding terrain are also a factor in determining the exposure category.
The concern over flying debris also effects other building elements. BC 1609.1.2 now calls for impact resistant glazing up to 60 feet above grade and 30 feet above buildings within 1500 feet that have aggregate roofs. Louvers also must be impact resistant within 30 feet of grade. The effect of Sandy’s winds are lingering long after the storm has passed. Designers of both low and high rise buildings must take this new reality into account for the overall building design and it’s components.