The Difference in Metal Roofing Panel SubstratesDecember 28, 2022

What are Panel Substrates?

Panel Substrates are a key component to a metal roofing system that rest under the metal panels. These are sometimes referred to as underlayment or roof decking. Panel Substrates have two main functions:
  1. Structural: transfers weight to supporting joints.
  2. Base: acts as a base attaching the metal roof using clips and fasteners.

What are the types of substrates?

  • Plywood- easy to install and affordable, but may weaken over time
  • Solid Timbers- durable and water resistant, but prone to warping
  • SPF Substrates (Spray-in-Place Foam)-can help pitch a roof and act as an insulator but needs support and is dependent on the quality
  • Concrete- great structural integrity which makes it perfect for multi-story buildings, but is limited to the type of roof coating that can be used.
  • Metal- there are several metal substrates with galvanized and aluminum being the most popular. They are strong, lightweight, and moisture-resistant.

Aluminum, galvanized, or galvalume?



Steel and aluminum substrates are both well-performing materials. However, aluminum has both pros and cons over steel. Aluminum is a lighter material, so if weight is a factor, aluminum would be a better choice. However, aluminum is more expensive than steel. It is more resistant to seawater corrosion than steel and is more malleable. However, steel is inherently stronger.


Galvanized and Galvalume are both types of steel substrates; the difference being their coatings. Galvanized substrates are coated with a zinc alloy. Due to the higher amount of zinc, there is greater protection against panel corrosion. This allows for increased panel longevity and long-term aesthetics.


Galvalume is coated with zinc, aluminum, and silicone. Galvalume is the most durable of the 3 metal substrates discussed. Galvalume has been proven to have superior performance and is superior in corrosion resistance, making it the optimal choice for marine sites. Additionally, most galvalume substrates have warranties.   Please contact Sentrigard’s Roofing Technical Services team for more information regarding metal substrates and warranties.

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