Roof Underlayment Materials: A Comprehensive Guide

Choosing the right roof underlayment material is crucial for a durable and watertight roof. It's a layer that protects the roof deck from moisture and damage, and can make or break the longevity of your roof.

One of the most common types of roof underlayment is felt paper, which has been used for decades. Felt paper is made from asphalt-saturated paper and is relatively inexpensive to install.

There are also synthetic underlayment options available, such as polyethylene and polypropylene. These materials are more durable and resistant to tears than felt paper, but can be more expensive.

In addition to felt paper and synthetic underlayment, there are also modified bitumen underlayment options. These materials are made from a combination of asphalt and rubber, and are known for their high durability and resistance to tears.

Roof underlayment materials come in various forms, each with its own set of features and benefits.

There are six main types of roof underlayment, including Asphalt-Saturated Felt, Rubberized Asphalt, Synthetic, Self-Adhering, Waterproof, and Foam. Each of these types offers unique characteristics, such as durability and waterproofing properties.

Here's a breakdown of the main types of roof underlayment:

Underlayment is a vital part of the roof that provides another layer of protection beneath the shingle, preventing leaks from getting into your house.

It's semi-breathable, allowing air and humidity to flow from the deck below, which is essential for keeping your roof functioning for years to come.

The main purpose of underlayment is to protect the roof deck below with a watertight seal.

It's designed to prevent water from seeping into your home if the shingle has a leak, making it a crucial layer of protection.

Underlayment helps keep your roof functioning for years to come, which is why it's not hard to see why it's essential.

See what others are reading: How to Build a Lean to Roof over Deck

The type of roof underlayment you choose will depend on several factors, including the type of roofing material you're using and the climate where you live.

Cost is always a consideration, but it's essential to balance budget with the need for a high-performance roof system that will protect your home from water damage.

In areas with high winds and rain, such as Florida, a more robust underlayment like VaporDry SA self-adhered acrylic roofing membrane may be worth the investment.

If your attic is conditioned, you'll want to choose a vapor-permeable underlayment like VaporDry SA to help moisture escape and prevent rot.

Felt paper is a popular choice because it meets code and is less expensive, but it can be a hassle to install and may require extra steps to fix tears and wrinkles.

Here are some key factors to consider when choosing the right roof underlayment for your project:

Ultimately, the right roof underlayment for your project will depend on your specific needs and circumstances.

Asphalt-saturated felt underlayment is a traditional and widely used option for roof underlayment. It's made from a base mat saturated with asphalt for water resistance.

Asphalt-saturated felt comes in two thicknesses: 15-pound and 30-pound. The 30-pound felt is thicker and heavier than the 15-pound felt. The 15-pound felt is thinner and lighter, making it easier to handle and install.

The pros of asphalt-saturated felt include being easy to install, budget-friendly, and light and pliable. It's a good option for steep-slope roofs and metal roof underlayment material.

Here are the key options to consider:

Felt underlayment is made from recycled corrugated paper mixed with sawdust.

It's available in different types, including organic reinforced and inorganic reinforced.

Synthetic underlayment is a far superior product compared to felt, made from laminated polypropylene or polyethylene plastic.

Synthetic underlayment has superior tear resistance and durability compared to felt.

If you're on a tight budget, felt might be the obvious choice, but it requires immediate placement of shingles.

Asphalt-saturated felt is a traditional roofing underlayment that's been used for decades. It's made from organic or fiberglass material saturated with asphalt, which makes it water-resistant.

Asphalt-saturated felt comes in two main thicknesses: 15-pound and 30-pound. The 30-pound felt is thicker and heavier than the 15-pound felt, but it's also more durable.

One of the benefits of asphalt-saturated felt is that it's easy to install, which makes it a great option for DIY roofers. However, it's not as durable or resistant to damage as other options.

Asphalt-saturated felt is also budget-friendly, which is a major advantage for many homeowners. It's much cheaper than other options, but it still provides effective protection for your roof.

Here are the key differences between 15-pound and 30-pound asphalt-saturated felt:

Overall, asphalt-saturated felt is a reliable option for roofing underlayment, but it's not the best choice for everyone. If you're on a tight budget and need a quick solution, it's definitely worth considering.

Synthetic sheet underlayment is a relatively new concept, having only been on the market for the past 20 years. It's made from polypropylene or polyethylene and a polymer to form an all-over protective barrier for a roof.

Synthetic underlayment is a more expensive alternative to felt, but it's a very durable option made of plastic polymers like polyethylene. It's far easier to work with than felt because it's lightweight and won't wrinkle or rot as easily.

Synthetic underlayment is available in various types, including ones made from materials like polyethylene, polypropylene, polyester, or fiberglass. These types offer durability, tear resistance, and waterproofing.

Here are some key features of synthetic sheet underlayment:

Sharkskin is a type of underlayment material that's gaining popularity among flooring installers. It's made from a unique blend of polypropylene and polyester fibers.

Sharkskin is known for its high density and water resistance, making it an excellent choice for areas prone to moisture, such as bathrooms and kitchens.

The material's unique texture also provides excellent grip and stability, preventing the flooring from shifting or moving over time.

One of the key benefits of sharkskin is its ability to reduce noise levels and provide a smooth, even surface for flooring installation.

Synthetic sheet underlayment is a relatively newer concept, having only been on the market for the past 20 years.

It was created as a solution to fix the problems with felt underlayment. Synthetic sheet underlayment is a more expensive alternative to felt.

It's usually made of plastic polymers, such as polyethylene, and it's a very durable option. This makes it far easier to work with than felt.

Synthetic underlayment is very lightweight, which makes it easy to handle and install. It won't wrinkle or rot as easily as felt because it's made of plastic rather than organic materials.

Synthetic underlayment can last a while longer than felt, making it a worthwhile investment for some homeowners. It's also more weather-resistant on its own, so you won't have to rush to get shingles on after it has been installed.

Foam is a type of synthetic roofing material that provides insulation and waterproofing benefits. It's often self-adhering, making it easy to install.

Foam underlayment offers strong resistance to wind and guards the roof from wind-driven rain. It's a great option for most climates.

This type of underlayment can also be an SPF, or Spray Polyurethane Foam, which is a foam underlayment applied directly to the roof deck using specialized spray foam rigs. SPF offers thermal resistance.

Here are some key benefits of foam roof underlayment:

Pre-weatherized sheathing combines two products in one—a sheathing with an integrated weather barrier—allowing for faster roof construction and a quicker dry-in time.

It's a versatile option and can also be specified in insulated panel options.

Installation of pre-weatherized sheathing requires precise taping at seams.

Over-driven fasteners can create an entry point for water if not treated with care.

ProArmor is a great option for synthetic roof underlayment. It has dual-surface slip resistance, making it a safe choice for roofing projects.

You can leave ProArmor exposed for up to 90 days, which is a convenient feature if you're working on a project that takes a bit of time to complete.

It's available in 42” rolls, making it easy to work with and store.