Cover Board 101

When it comes to selecting the products for your commercial roofing system, it can easily become overwhelming. One product that should be included in every roofing system is a cover board, a relatively thin, semi-rigid board installed between the insulation and the roofing membrane.

These products provide protection, separation and support for the roofing membrane, helping protect it against damage from a wide variety of situations. The National Roofing Contractors Association recommends using cover boards with polyisocyanurate insulation to minimize a variety of problems with:

  • Facer-sheet delamination
  • Cupping or bowing of the sheet
  • Crushing or powdering
  • Cavitation at the edges of the sheet
  • Shrinkage

In addition to providing protection, cover boards can help improve roofing assemblies in a variety of ways. They can enhance or reduce fire resistance of the entire assembly and increase resistance against moisture coming from leaks, condensation or rain, or moisture that is introduced during construction. Adding a cover board can also enhance the strength of the entire roofing system, helping it withstand loads from construction and maintenance traffic, hail impact, wind uplift and snow loads.

There are a variety of cover boards available, and the most commonly used types include:

  • Asphaltic board
  • Paper faced gypsum
  • Glass-mat gypsum
  • Perlite
  • Mineral fiber board
  • Wood fiber board

Each type of cover board varies widely in its performance characteristics, so it’s important to compare each one before determining which is the best for your project. The key parameters for comparing performance should include fire resistance, moisture resistance and strength. Use the charts below to compare the performance of the most common cover board types in these critical areas.

Contact your local Garland representative to learn more!