NY State Building Codes- Roofing Specifications
In 2003 New York State chose to adopt the newly defined standards established by the federal government. With concerns for our limited energy supply and the cost to the federal government as the result of natural disasters (hurricanes) the government has taken on the responsibility of ensuring that structures are made safer and energy efficient. As a result a recent wave of regulations have been developed by the Federal government and adopted by the State of New York. Based upon the current NEW YORK STATE BUILDING CODES there are several conditions which must be addressed prior to finalizing the roofing specifications which will be used on a building in the state of New York.
The first issue is that the Building Code includes specific Energy Codes requiring that a minimum R-20 (thermal resistance) is achieved based upon the amount of insulation included within the new roof system being installed. When roofing a commercial building a rigid foam insulation 3.3” thick must be included. However, if you are performing a reroof (installing a new roof while leaving the existing roof system in place) you are not required to meet this code.
The next consideration is that at the time of a reroof the specifications for the new roof system must provide positive pitch. This means that the installation must provide some means for the water to drain off of the roof. The requirement, as it applies to a reroof, is not specific as to how much pitch must be provided, only that the roof can not be dead flat. The typical way of achieving pitch during a reroof is to install tapered insulation, the most commonly used insulation has 1/8” pitch for each horizontal foot. In the case of new construction, however, you must provide 1/4” pitch. The most cost efficient method is to pitch the deck during construction which allows the roof system to simple comply with Energy Code. But on occasion 1/4” tapered insulation is used on structures with a level roof decks.
The next consideration is that on all reroofs after January 1, 2003 it is no longer permitted to install a third roof on a building. This requirement applies to buildings with either flat or pitched roof decks. The purpose for this code is to provide for the safety of building occupants. Many buildings have been constructed prior to strict weight load studies. Therefore, the code is intended to avoid having the weight of multiple roofs overburden the structural limits of a building.
While this requirement has the effect of increasing the cost of a roofing project it is almost always better to remove the existing roof prior to the installation of a new roof system. When reroofing flat buildings it is not uncommon for there to be moisture trapped within the existing assembly as a result of the leaks which have caused the owner to decide to reroof the building. This trapped moisture will expand and contract after a reroof and studies have shown that the moisture will take years to dry. During this time the water will be causing the entire assembly to deteriorate prematurely.
In the case of pitched roofs the reroof of a structure will eliminate valuable air flow qualities in the system and cause the shingles to fail prior to their intended life expectancy. This is because the shingles will super heat and the petroleum components will dry out more quickly than normal.
A relatively new component of the building codes is the wind uplift specifications. Historically the insurance industry, Factory Mutual, was the leader in the study of the cause of roof blow-offs. They were motivated to do this because they covered the building owner for the loss of the roof and any interior damage during a wind event. Therefore, FM has studied thousands of failures and designed a series of wind uplift specifications which allow a roof system to meet I60 through I120 wind load requirements.
This code provides increasingly stringent requirements as the risk of blow-off increases based upon the location of a building, what is around it, the height of the building, vertical openings (doors and windows) in the structure, etc. As a result of these studies the Building Code requires the use of six nails (versus the standard four nails) if a structure is within one mile of the shoreline.
This report is intended to act as a summary of the basic requirements when a building owner is considering installing a roof on their building. I t should demonstrate the need to have a qualified roofing contractor able to analyze a structure and determine what the code means to the design of the new assembly.
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