Fiberboard vs. Perlite Cover boards: Here’s Everything You Need To Know

perlite cover board installation

According to the CRCA, cover boards have become something of a standard practice for low-sloping roofs. Made of homogeneous materials and formed into boards, they are used over roof insulation to provide protection and a smooth surface during installation. There are several options for cover board materials, each with pros and cons based on the method of installation. This week, we’re focusing on Fiberboard and Perlite cover boards, and why they may work  (or may not work) for your structure.

Fiberboard Roof Cover Boards: 

fibreboard example

Advantages: 

According to Roofing Canada, “cellulosic fiberboard is the most widely used cover board material used in roofing.” One of the main reasons that this material is so popular is its flexibility. Fiberboard is available in multiple thickness and board sizes, and can be treated with different additions (asphalt, clay, or paraffin) to enhance its moisture resistance and compatibility with different kinds of membranes.

Fiberboard also comes in a range of densities, which may be indicative of their compressive strength.  This makes this kind of cover board ideal for high-traffic roofs. Because of its composition, fiberboard cover boards are made from recycled materials, making it a great option for companies who wish to remain eco-friendly.

Disadvantages: 

Fiberboard is a combustible cover board material, therefore contact with direct flame or high temperatures should be avoided. This unfortunately makes it impossible to use this cover board with any membrane that requires a direct torch applied base layer, and is not recommended for structures where fireproofing is a top priority.

Fiberboard systems must also be sealed in order to protect from water damage. Water damage with this particular board will cause the material to permanently expand and warp, which may necessitate repairs.

Key Takeaways For FiberBoard: 

Pros: 

  • Durable and impact resistant
  • Cost effective
  • Environmentally friendly option
  • Appropriate for low-slope roofs.

Cons: 

  • Needs to be sealed for moisture protection
  • Not ideal for flammable environments

Perlite Roof Cover Boards: 

perlite cover board diagram

Advantages: 
Perlite roof insulation, in contrast to fiberboard, is a fire resistant cover board option for your roof. Perlite is a tried and true cover board method, which, according to Roofing Canada, has been used since the 1950’s. Perlite boards are composed of expanded perlite ore, fiber, cellulose fibers, asphalt, and starch binders. Most often, perlite cover boards are made from recycled materials.

Perlite cover boards provide excellent dimensional stability, are water-resistant and lightweight. This makes the installation process much simpler in comparison to heavier cover board materials.

Disadvantages: 
Insulation with higher moisture content may cause blistering during application, the risk of which is increased if there is high humidity. However, your roofing professional should be able to avoid this with expert application.

Key Takeaways For Perlite: 

Pros: 

  • Fire resistant
  • Dependable and widely used
  • Eco-friendly

Cons: 

  • Higher moisture content means that this type of cover board is at risk for blistering

Roofs are made with a combination of multiple materials that work together in order to support the overall function of your building. That’s why there are so many different material options and combinations. If you’d like to learn more about cover board options, click here. If you’re not sure which cover board option is right for you, or have general questions regarding your roof, contact us, we’re here 24/7 to ensure your roof is at its best.