In 2004 most states and municipalities adopted the new “International Building Code” (IBC). This code differs dramatically from the previous building codes in many ways. The most important to you and your project is how it looks at the design load for wind uplift pressures subjected to the roof. Different from years past, the roof is now divided into three zones: The “Field” or central areas of the roof, the “Edge or Perimeter” and the “Corner” zones of the roof. The loads for each “Zone” as shown in the below illustration must now be calculated separately to determine attachment points of the new roof panel system to the Roof Hugger framing system. Essentially, these locations are the same as “Panel Clip” spacing in the case of standing seam metal roofs or fastener placement for thru-fastened metal roofs. It is very important to understand that the required locations of new Roof Huggers on the existing roof will be governed by the new metal roof system’s ASTM E-1592 tested values.
The new roof must withstand the full forces calculated for each of these “Zones” on a per project basis. It is important to understand that code based reductions allowed in the past are usually no longer permitted. Since no two buildings are exactly alike, the size and shape of these “Zones” vary from building to building and depends on numerous factors. Included in these factors are height above ground, roof geometry, exposure of the roof to surrounding obstructions, distance from coastal areas, etc. Each building must be considered individually and engineered based on the existing conditions and proposed changes. The basic steps in the evaluation process are as follows:
If you need assistance with the above process please feel free to call Metl-Span Estimating: 877-585-9969 to discuss your specific project.