Synthetic Roof Underlayment Vs. Felt

Getting suitable roofing materials can be difficult sometimes since there are different products available on the market. So, if you need a roof replacement, it’s advisable that you learn about the materials that make up your roof. Roof underlayment is one of the important roofing materials you need to know.

Synthetic and felt roof underlayments are the two common types of underlayment, particularly for residential roofing. As common materials which you can easily see, it would be great to know which one is the best.

There are lots of differences between synthetic roof underlayment and felt. Some include how synthetic underlayment is more expensive yet more durable, lighter, and easier to install than felt roof underlayment. Also, synthetic underlayment offers extra protection (better resistance to tearing) and increased stability.

Synthetic Roof Underlayment Vs Felt

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Synthetic Roof UnderlaymentFelt
DurabilitySynthetic roof underlayment is more durable. It holds nails better and efficiently repels water rather than absorbing it. In other words, this roof underlayment features extra strength and helps protect the roof from weather better than felt roof underlayment.Felt roof underlayment is not as durable as its synthetic counterpart. In fact, it’s much more susceptible to rip during the installation process or from high winds. Also, it’s a roof underlayment that gets wrinkled if it absorbs water or moisture during exposure. This explains why you must install shingles not too long from when felt roof underlayment is laid down.
LightweightWhen it comes to weight, synthetic roof underlayment is lighter than felt roof underlayment. In some cases, synthetic weighs 4 times more lightweight when compared with felt.Felt roof underlayment is not as light as its synthetic counterpart. It’s a heavy material, making it have less material per roll than synthetic. With this, installers will need more of it, which will cost more time and energy to take up the ladder during installation.
InstallationSynthetic underlayment is easy and fast to install. It’s lighter, making it more on the roll than felt. With this, installers will enjoy reduced numbers of trips between the roof and the ground getting new rolls. Also, it features a slip-resistant surface, making it possible for installers to walk confidently on the roof without worrying about sliding off.Felt roof underlayment can be very slippery, which poses a great challenge for installers since they have to be extra cautious while walking on it.
PriceSynthetic is more expensive than felt. It costs around $7 to $10 per square.Felt roof underlayment is cheaper when compared with its synthetic counterpart. So, if you’re on a budget, it’s the best option. It costs around $5 per square.
WaterproofSynthetic roof underlayment is not waterproof but water-resistant.Although felt roof underlayment is not waterproof, it is water-resistant and breathable. Its breathability is a significant advantage for roofing materials such as asphalt shingles. It adds to shingles’ longevity since the plywood roof deck can breathe.

Differences Between Synthetic Roof Underlayment and Felt

We have elaborated some differences between synthetic roof underlayment and felt below. Please go through them to know more about how they are not the same.

Synthetic Roof Underlayment

What We Like

  • Lightweight: Users will enjoy the fact that synthetic roof underlayment is lighter than felt roof underlayment. It’s even claimed that it’s 4 times lighter, making installation super easy and fast. This is due to how installers won’t stress themselves too much moving up and down the ladder getting more rolls– the roofing material has more on a roll.
  • Durable: Synthetic roof underlayment is undoubtedly tough, meaning that it will take time to tear. Also, its strength will make it less prone to damage when installers walk on it. In a situation of being exposed to moisture or UV for a long time, it will still last longer.
  • Safer when installed: Many synthetic underlayment are with a slip-resistant surface.  This makes it less dangerous (sliding off) when installers walk on the roof.

What We Don’t Like

  • Price: When compared to its felt counterpart, synthetic underlayment costs more. But it may sometimes be worth the cost if you want to stay in the house for many more years.

Felt Roof Underlayment

What We Like

  • Price: Felt roof underlayment is cheaper when compared with synthetic roof underlayment. This is a tremendous benefit for those with lower budgets.
  • Supports common tools: Unlike synthetic roof underlayment, felt roof underlayment allows common tools for the installation process.
  • Breathable: Even though felt roof underlayment is not waterproof, it’s water-resistant and breathable. This is an added benefit for roofing materials. Besides, it makes shingles live longer since the plywood roof deck can breathe.

What We Don’t Like

  • Less exposure: By exposing felt roof underlayment to the elements for a length of time can get it damaged. So, it’s advisable to install it as fast as possible when the felt is down– not doing this can lead to a leaky roof.
  • Prone to tear and wrinkle: Felt roof underlayment tears easily. This can occur when it’s windy during installation.  Besides, it can wrinkle and harden if exposed to moisture during installation. This can make laying shingles flat nearly impossible.
  • Very slippery: Unlike synthetic roof underlayment, which is tough, felt roof underlayment places installers at risk of sliding off when walking on it.

Frequently Asked Questions (FAQs)

Is felt underlayment better than synthetic?

When it comes to durability,  synthetic roof underlayment has the upper hand. It also holds nails better and impressively repels water. Notwithstanding felt roof underlayment is cheaper.

How do I choose a roof underlayment?

To choose a roof underlayment that offers a highly significant amount of protection, you can check the ratings. The ratings are from A to C. A is the best, offering high-grade protection against fire. C is the lowest, providing the least fire resistance.

Will synthetic underlayment leak?

Synthetic roof underlayment is exceedingly durable. It’s less prone to tearing, and when installed properly, it is less susceptible to leaks.


To choose the most suitable type of roof underlayment, you must consider several factors. Some of these include the cost and protection.  Synthetic roof underlayment is a better choice if you can afford it, but if you’re on a budget, you may opt for felt roof underlayment. If you need further assistance to decide the best roof underlayment for you, please speak with local roofing professionals.

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