Pros of felt underlayment:

• It is the least expensive option.
• It is water-resistant, which helps keep water from penetrating the surface if any leaks through the roofing structure.
• It is available almost anywhere because it is more commonly used.

Cons of felt underlayment:

• It does not last as long as synthetic
• It may not respond well to high-temperature environments.
• It cannot be left exposed for a significant amount of time. It can be vulnerable to rips from high winds.
• Asphalt is made from petroleum, which is a highly flammable substance and brings a concern for fire resistance.

Synthetic sheet underlayment

Synthetic underlayment is a newer innovation that is taking over the metal roofing industry as a better, more advanced replacement for felt underlayment. Synthetic underlayment is a roofing accessory created by weaving/spinning together polypropylene or polyethylene and a polymer to form an all-overprotective barrier

Pros of synthetic sheet underlayment:

• Synthetic is very light compared to felt.  Most roofers prefer this material because of its weight, it goes on faster and covers more area.
• It typically has a longer lifespan than felt underlayment.
• It is more durable because it is developed with thermoplastic polymers. It is more resistant to tearing, moving, and other types of damage.
• It has a tolerance for high temperatures.

Cons of synthetic sheet underlayment:

• It is more expensive than felt underlayment.
• It has a low permeability rating (which is good for keeping out moisture), but that will also make it more difficult to have proper ventilation.

High Temp Underlayment

Pros of high temp underlayment:

• Peel-and-stick allows a high temperature suitable for metal roofs.
• Helps make low slope roof conditions weather-tight
• Protects high risk areas on the roof.
• Unlike traditional felt paper, a peel-and-stick underlayment’s rubberized features keep it from easily tearing thus providing consistent protection while being installed and against severe weather.

Cons of high temp underlayment:

• It can be more expensive than the other options.

At the end of the day, each product has their own pros and cons. It will come down to what is most important to you. In every case, it is best to consult a professional to determine which underlayment would be best for you.

How long do you want to have the roof? Does your budget allow for a more expensive underlayment? Are you concerned about it being fire resistant? Those are typical questions you will have to think through when deciding what is best for you and your situation.

If you would like to discuss more about what underlayment would be best for your situation, please contact us at one of our 21 branch locations.