Felt Underlayment vs Synthetic Underlayment
Roofing underlayment is the layer of protection that is between the roof deck (the plywood base of your roof) and the shingles. There are two different options you could use as underlayment: synthetic and felt. While there are pros and cons to both, each product will help give your roof the extra layer of protection it needs. The type you need for your roof may depend on the geographical location of your home, the other materials used for your roof, your roof’s design, or your budget, so be sure to speak with your roofing contractor to see what their suggestion is before selecting one over the other.
Felt Underlayment is one of the oldest types of roofing underlayment and is created by saturating either paper or a fiberglass mat with asphalt. It’s typically available in two types: No. 15 and No. 30. When compared, No. 30 is usually thicker, stronger, and less prone to tearing or ripping off during installation or weather events.
Pros:
Cost - Felt underlayment tends to cost less than synthetic underlayment, and is often the go-to for homeowners on a budget.
Cons:
Exposure - When exposed for more than a few hours, the material is prone to drying out or leaching oils in the heat.
Wrinkling - When exposed to moisture, the mat can absorb water and the felt can wrinkle which makes it harder for the shingles to lay flat. To help prevent this, it is best to install the shingles immediately after the underlayment is installed to ensure optimal protection.
Prone to Tearing - Tears easily in high winds and during installation.
Slippery Material - Since the material is slippery, it can make it harder for roofers to walk on after installment and can make it dangerous for them.
Heavier Material - Since it’s heavier than synthetic underlayment, it can make it harder for the roofers to install and it also will have less material per roll. This means you will have more seams instead of a single course with no lapses.
Warranty Issues - Depending on your manufacturer’s warranty, felt underlayment may not be protected. Be sure to talk to your contractor about wether or not it’s covered if this is the route you are going with.
Synthetic Underlayment has more enhanced water-resistance and protection from the elements and is usually made from long-lasting polymers which provide added strength and longevity. When installed correctly, it offers better protection from the weather compared to felt.
Pros:
Tough Material - Since the material is tougher than felt, it typically doesn’t tear and can still perform as designed after the workers have walked on it.
Fast to Install - Since it’s a lighter weight than felt and there’s more on a roll than felt underlayment, synthetic underlayment is faster to install.
Less Slippery - Since the material is less slippery than felt, it is safer for the workers to walk on after installing on the roof. It is also more durable so it won’t rip as easily.
Moisture Resistant - Synthetic underlayment is built to repel water, and is more suitable for extended UV and moisture exposure.
Eco-Friendly - While it is still made of plastic, it is more eco-friendly than asphalt felt as it can be recycled.
Cons:
Cost - One of the main cons to synthetic underlayment is the cost. However, the cost may end up being worth it when compared to felt due to the higher quality of the material.
Non-Standardized - Being a non-standardized material, synthetic underlayment can be made differently depending on the manufacturer and may therefore have different levels of performance. Be sure to do your research and talk with your contractor to help select the right type of synthetic underlayment for your roof.
After comparing the two underlayments, synthetic seems to take the cake. Although it might cost you more at the moment, it will more than likely pay off because it is better quality than felt and will probably last longer. However, as mentioned above, it is important to consider other factors such as location, budget, roof design, and more. Make sure to speak with your contractor about which option is best for you and your home before making a decision.
