Underlayment for Metal Roof and the Material Types

Underlayment is a layer that is put underneath the metal roof as the waterproofing method and thermal protection for a building. It is considered important, as the metal roof can be scorching on summer days due to high temperatures, cold during winter, and loud during rainy weather.

However, choosing underlayment for metal roof is a matter of its own. Read and learn how to pick the best and most suitable material for it in the following.

Best Underlayment for Metal Roof

You might have wondered, what do you put under a metal roof? The answer is underlayment, which is consisted of waterproof or vapor barrier material. This piece is installed on the roof system’s decking directly to combat extreme weather and climate circumstances.

Underlayment for Metal Roof

If you aren’t using underlayment for a metal roof, the roofing system and the rest of the building might be exposed to elements such as moisture, wind, resin, or chemical.

Read also: Metal Roof Underlayment

Selecting the best underlayment is important to maintain the lifespan of your home. There are three underlayment types that most commonly available, that you can read about below:

Felt underlayment

This underlayment might be referred to by different names such as asphalt felt, roofing tar paper, or felt paper. Compared to the other two, it is the most used material type because it is easy to find almost everywhere and is more affordable.

Synthetic sheet underlayment

The second underlayment material is relatively new but has gained popularity in its respective industry recently. A synthetic sheet is a protective barrier made by spinning or weaving polypropylene or polyethylene together with a polymer. Compared to felt material, it is more expensive but has better durability.

Self-adhering membrane underlayment

The last material of underlayment is the self-adhering membrane, which is the type of peel-and-stick item adhered to the roof deck. It’s considered the most suitable for high-temperature underlayment because it can resist temperatures up to 240ºF.

However, it might perform rather poorly at low temperatures.

Synthetic Metal Roof Underlayment

As mentioned in prior, synthetic underlayment is a newly innovated material that’s currently taking the industry over. This protective sheet layer is considered a good underlayment to use on metal roofs because of its qualities. Here are the advantages and disadvantages of using this material:

Synthetic Underlayment for Metal Roof


Many homeowners choose to use synthetic sheet because:

  • It generally has better durability compared to the felt underlayment
  • It has a higher resistance to various types of damage, moving, or tearing because it is created with thermoplastic polymers.
  • It has quite a good tolerance for extreme temperatures.


The downsides of using synthetic sheet underlayment for a metal roof are:

  • It is pricier compared to the felt underlayment
  • It has a low rating or permeability, so it is not the best material to have proper ventilation, but otherwise is great to combat moisture.

Is Underlayment Necessary for Metal Roof

Metal is definitely a durable material for the roofing system. In fact, they can last up to 70 years. Its resistance to weather such as blizzards or rainstorms and its excellent durability are part of why it is commonly used worldwide.

However, it still needs to be taken care of to last as long as it should. If you still wonder if adding underlayment for a metal roof is necessary, then the answer is yes! Underlayment is highly recommended to be added to metal roofing.

There are many potential issues if you choose to go without it, such as roof leakage, trapped moisture, and other problem assortment that might deteriorate the quality of your roofing system and reduce the metal roofing’s longevity in the future years to come.

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RoofLast is an experienced author and roofing expert. With years of practical experience in the field authored several informative articles on various aspects of roofing, including installation, maintenance, and repair