Frequently Asked Questions
1. How are expansion and contraction handled since the panel clips are not slotted?
Expansion and contraction are accommodated by thermal bowing of the panel between its attachments to the roof structure and is equally divided between the individual spans.
2. Do the panels provide useable diaphragm load for helping brace the building structure?
Unlike single-skin, standing-seam roof systems, the CFR roof system when installed with Metl-Span diaphragm clip provides structural diaphragm. Consult Metl-Span’s engineering department for details and capacities.
3. What is the minimum recommended roof pitch?
Recommended roof pitch for CFR minimum is 1/2″ in 12″.
Why are CFR panels typically not recommended for pitches less than ½” in 12”, like many single skin trapezoidal rib panels?
The panels when installed must resist momentary flooding, such as that caused by heavy rain and wind gusts. In addition to typical loads like HVAC equipment, CFR roof panels are subject to potential ponding at the endlaps when the roof bows under thermal load. Single skin panels on the other hand expand and contract linearly rather than by bowing up between the structural supports.
4. Do the panels meet the uplift requirements of Factory Mutual 1-90, Factory Mutual 4471, Underwriter’s Laboratories UL-90, ASTM E-1592 and Florida Building Code?
CFR roof panels have been tested and have received approval for Factory Mutual 1-90, Factory Mutual 4471 and UL-90. The panels have also been subjected to ASTM E-1592 and Florida Building Code testing with acceptable results.
5. Do the panels meet code requirements for a Class A roof covering?
CFR roof panels meet Class A fire classification requirements of the major model building codes.
6. How are roof penetrations handled?
Penetrations for small pipes and ducts may be flashed with standard metal roof pipe flashing consisting of a flexible boot and a metal-backed sealing flange. For larger penetrations, a curb is attached to the roof to close the perimeter of the opening. Curbs must be purchased from specialty manufacturers.
7. Will the panels support foot traffic?
The panels will support foot traffic during erection and for roof and equipment maintenance. However, the panel should be protected from excessive wear and tear by the application of a proper roof walkway system.
8. What is the biggest advantage of CFR roof panels over a single skin standing seam panel?
CFR roof panels are factory assembled self-contained units consisting of roof weather membrane, roof insulation and liner decking. This provides factory control of the roof’s materials, fit-up and performance, eliminates the potential for misapplication of the vapor barrier and provides the efficiency and control of a single-source installation for the complete roof system. One-step installation process assures rapid completion of the roof system. Multiple steps to separately lay down a deck, vapor barrier, insulation and a metal panel or membrane are eliminated.
9. What is the maximum panel length available and how are long runs from ridge to eave accommodated?
The typical maximum length is 50’. Endlaps are required for longer runs from ridge to eave. Endlaps consist of an extension of the top metal skin of the panel and butt joining of the foam core and the bottom skin. The end of each panel is supported by the roof structure. The lapped faces are sealed with specially designed sealants and fasteners to create a gasket-type joint that effectively resists water penetration.
10. Are weather-tightness warranties offered for CFR panels?
Various weather-tightness warranties are available depending on the level of coverage that is desired by the customer. Metl-Span engineering and marketing must review the architectural and structural blue-line drawings to determine whether the project will qualify for a weather-tightness warranty.
11. How do the insulating characteristics of the CFR roof system compare to other insulation systems used in roofing?
The CFR roof system provides a uniform insulation value of R8 per inch. The insulation value of polyisocyanurate boards is R6.25 per inch, extruded polystyrene is R5.5 per inch and fiber glass is R3 per inch. A unique characteristic of Metl-Span’s polyurethane foam is the increase in thermal resistance that occurs as the mean core temperature of the panel decreases.