Cover Boards for Low-Slope Roofing Systems
Learning Objectives:
- Discuss durability, fire resistance and energy efficiency benefits to using a cover board in the design of a low-slope roofing system.
- Assess the external factors impacting the long-term performance and energy efficiency of a commercial roof system.
- Compare the different types of cover boards available and identify which type to use on various low-slope roofing systems to prevent moisture intrusion, mold, wind uplift and other external factors.
- Explain the pros and cons of various cover boards to help prevent threats to the roof and occupant wellbeing from fire, moisture, wind, sound intrusion and foot traffic.
Credits:
A well-designed building is only as durable as the roof that protects it. Without a properly designed, specified, installed and maintained roof, the building below it will suffer. The reputations of the building professionals involved will also suffer. For a relatively minor investment, roofing cover boards solve many issues that cause damage to a roof during installation and into the warranty period.
Potentially negative forces on a roof include fire, wind uplift, impact and hail, moisture, mold, sound intrusion and foot traffic.
Low-slope and flat roofs endure more additional stresses than ever before, from unpredictable weather events, to increased usage for photovoltaic, staging for large HVAC equipment and the workers who install them, to a growing trend toward “green roofs.”
“The roof is a commercial building’s first line of defense from natural hazards such as wind, rain, fire, hail, ice, snow, and extreme heat.,” states the Insurance Institute for Business & Home Safety. “It is also the most vulnerable part of your building.”i
In this article, we’ll discuss cover boards as part of a well-designed, smartly specified, properly installed low-slope roofing system. We’ll talk about where a cover board fits into the whole design, the different types of roofing systems, the different types of cover boards, and which boards perform best in which applications.
Overview of Low-slope Roofing Systems
A roof is not just one element; it is an assembly, where all components perform together.
The typical low-slope roof assembly consists of the following components:
- Structural roof deck — steel, concrete or wood.
- Thermal barrier (if applicable).
- Insulation, including such rigid foam types as polyisocyanurate (ISO), expanded polystyrene (EPS) and extruded polystyrene (XPS).
- Fasteners and/or adhesives, including mechanical fasteners, low-rise adhesives, rock ballast or concrete pavers, hot asphalt or cold-applied liquid adhesives.
- Cover Board.
- Membrane system, with types including single ply systems such as thermoplastic membranes (TPO, PVC) and thermoset membranes (EPDM). Also, there are asphalt-based systems, such as B.U.R. (built up roofing), or fluid applied, and polymer-modified bitumen. The latter are accomplished with torch (APP) or mop (SBS). Another type is spray polyurethane foam.
- Roof covering such as rock ballast, concrete pavers, coatings, etc. (if applicable).
In simplest terms, the cover board goes on top of the insulation and below the membrane.
Photo courtesy of National Gypsum®
For a relatively small cost, roofing cover board protect the roofing insulation and membrane from the negative forces of fire, wind uplift, impact and hail, moisture, sound intrusion and foot traffic. Above, workers lay out 1/4" glass mat roof board over high density poly ISO. Workers in the background mechanically fasten the assembly to the roof deck with plates and long fasteners.
Images courtesy of National Gypsum®
A roof is not a material or a product; it is an assembly.
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