This Web Exclusive comes from Metal-Era, Inc.
The roof is widely recognized as one of the most vulnerable parts of a building. Of the various components of a roof, the roof edge is the most critical because of the way in which wind acts on a building.
Commonly the roof edge receives little attention. It is considered simply an add-on accessory; however, careful selection of an appropriately tested edge is necessary to guard against the effects of potential wind damage. In addition to longevity issues, a tested edge is required by building code in many states and municipalities. This guide will walk you through the often confusing landscape of testing standards, code requirements and key issues related to choosing the appropriately performance tested roof edge for each project.
The Sheet Metal & Air Conditioning Contractors Association (SMACNA) has long been involved in providing guidance on metal gauges, cleat gauge and fastener placement through its recommended details. It is important to note that they provide no performance numbers to match jobsite requirements. The details are not tested to any performance standards and are a prescriptive standard,not a performance standard.
The National Roofing Contractors Association (NRCA) has also long been instrumental in providing guidance to roofing contractors and other design professionals. The NRCA supplies details for edge metal terminations, but is not and has no plans to become a roof edge manufacturer.
The NRCA has created a sub-listing process that is offered to NRCA members, but only limited details and select gauges have been approved. As of January 2006, only one contractor has been sub-listed for ANSI/SPRI ES-1. In order for the ES-1 requirement to be met, a sheet metal fabricator (contractor) must be individually approved and listed by the NRCA and Intertek Testing Services (ITS).
An explanation of the NRCA’s program for listing sheet metal fabricators is found in Mark Graham’s response to “Reader Clarifies FM Approval Information.” The article explains the sub-listing process as follows:
1. Payment of fees to NRCA and FM and/or ITS and execution of sublisting agreements
2. Payment of initial setup fee to NRCA and execution of a sublisting agreement
3. NRCA authorizes FM and/or ITS to begin their sublisting processes,which generally requires:
• Payment of fees
• Factory audit manual reports
• Inspections of the sheet-metal fabricator’s shop
• Execution of sublisting agreements
• Use of FM and/or ITS labels on all listed
edge metal flashings
• Periodic follow-up inspections to ensure continued compliance
For a contractor to meet the FM guidelines and now the ES-1 requirement,they must achieve two things:
• Use an approved detail
• Be an approved contractor
Both items must be in place for a metal edge to meet the code.
Factory Mutual (FM) is formed of a conglomeration of insurance companies.In order to limit their exposure to loss, FM has developed testing standards for materials used on the properties they insure.
This standard became popular to use even on buildings that were not FMinsured, simply because the roofing industry had no standard of its own. Meeting the FM Loss Prevention data Bulletin 1-49 does not make the edge ANSI/SPRI ES-1 tested. FM testing should not be confused with ANSI/SPRIES-1 testing; they are two separate and unique testing methods. Specifiers should carefully list which testing requirement(s) are needed for each building project. Likewise, roofers should fully understand the different testing methodologies in order to supply the appropriate product for each project.
The American National Standard Institute (ANSI) is a non-profit organization that does third party endorsements of performance testing processes and procedures. The Single-Ply Roofing Industry (SPRI) is comprised of manufacturers and professionals in the single-ply roofing industry.
The standard was canvased throughout the industry to develop consensus and followed the below steps on its way to becoming an international code:
1. Developed by SPRI
2. Approved by ANSI
3. Approved by ICC
4. Added to the 2003 IBC
The 2003 version of the International Building Code (IBC) includes the requirement that roof edges be ANSI/SPRIES-1 tested:
2003 IBC § 1504.5: “Edge securement for low-slope roofs. Low-slope membrane roof systems metal edge securement, except gutters, installed in accordance with Section 1507, shall be designed in accordance with ANSI/SPRIES-1, except the basic wind speed shall be determined from Figure 1609.”
Over half the country has adopted the 2003 IBC statewide and countless municipalities have done likewise.The trend is clear, and ES-1 testing is something that all roofing and design professionals will need to become familiar with.
The ES-1 document is called “ANSI/SPRI ES-1 Wind Design Standard for Edge Systems Used with Low Slope Roofing Systems,”and it can be downloaded for free on SPRI’s Web site.
The ANSI/SPRIES-1 standard is comprised of three pull-off tests: two tests for fascia and one test for coping.
The tests use a pull-release, pull-release method rather than a continuous pull. This allows for a realistic simulation of wind,which acts on a building in periodic gusts rather than one long, continuous gust. It is also important to understand that the corner of a building receives the most wind uplift stress, and that stress will suddenly increase and decrease with wind gust strength. The RE tests measure the following:
1. Ability of edge treatment to resist the pull of the roof material inwardly
2. Resistance of the edge to outward & upward forces which tend to blow or “peel”edge systems off
Roof Edge Test RE-1
• A static test with a 100 lb. load every foot
• The membrane is pulled at a 45˚ angle to the roof deck to simulate a billowing membrane
• The termination must withstand a minimum force of 100 lbs./foot
Roof Edge Test RE-2
• Determines the maximum load at failure
• Failure is the loss of securement of any component of the roof edge system
Roof Edge Test RE-3
• Simultaneously tests the vertical and horizontal wind gust load coefficient
• Failure is loss of securement of any component of the roof edge system
The equation for calculating the design pressure is found in “ANSI/SPRI ES-1 Wind Design Standard for Edge Systems Used with Low Slope Roofing Systems.” This calculation involves five key elements.
1. Building Height
The building height should be the height at which the roof edge is to be installed.If there are multiple roof levels, each level is considered a different building height.
2. Wind Speed
Use the ANSI/ASCE 7-02 document,“Minimum Design Loads for Buildings and Other Structures.” This document provides wind maps of the United States and its territories,which are to be used to determine the wind speed for a particular region.
3. Building Location (exposure level)
• Exposure A: Now classified as Exposure B
• Exposure B: Urban & suburban areas, single family dwellings
• Exposure C: Open terrain with scattered obstructions
• Exposure D: Flat, unobstructed areas; open water for one mile or greater
4. Building Occupancy Factor (importance factor)
• Category I: Buildings & other structures that represent a low hazard to human life in the event of failure (i.e.agricultural facilities, certain temporary facilities and minor storage facilities)
• Category II: All buildings & other structures except those listed in Categories I, III & IV
• Category III: Buildings & other structures that represent a substantial hazar
d to human life in the event of failure (i.e.buildings where more than 300 people congregate, elementary, secondary schools & daycare facilities with a capacity greater than 250 people, health care facilities with a capacity of 50 or more resident patients, but not having surgery or emergency treatment facilities and jails or detention facilities)
• Category IV: Buildings & other structures designed as essential facilities (i.e.hospitals & other health care facilities having surgery or emergency treatment facilities, fire, rescue & police stations & emergency vehicle garages and communication centers & other facilities required for emergency response)
5. Special Terrain Characteristics
Obstructions or special terrain characteristics such as hills, escarpments, etc. will influence the wind patterns on your building.
No area of the country is exempt from wind related roofing damage, and one of the leading causes of commercial roofing damage has proven to be improperly designed and installed edge details. Conservative estimates show that 75% of all wind-related roofing failures are attributed to insufficient or poorly installed perimeter metals.
It is important to check your local code requirements because additional states, counties and municipalities are in the process of adopting the 2003 IBC. Understandably, it can be difficult and sometimes confusing to keep track of each locality’s requirements, so in order to avoid the risk of not meeting the code, specify ES-1 tested roof edges.
In order to help design professionals choose a product that has been tested to meet the specific design requirements of each project, Metal-Era has developed a Wind Design Calculator. The calculator allows users to enter basic project data to receive the design pressure needed and a list of appropriate Metal-Era products. The testing provides customers with the piece of mind that they are not liable for a building code violation.