When it comes to roofing, underlayment is an often overlooked but crucial component of a well-constructed and durable roof. While it might not be as visible as the shingles or as exciting as choosing a roof color, the underlayment plays a vital role in protecting your home from the elements and ensuring the longevity of your roof. In this article, we will explore everything you need to know about roof underlayment, from its purpose and types to installation and maintenance.

What is Roof Underlayment?

Roof underlayment, sometimes simply referred to as “roofing felt” or “roofing paper,” is a protective barrier installed between the roof deck and the roofing material, such as shingles or metal panels. Its primary purpose is to provide an extra layer of protection against water infiltration, temperature fluctuations, and other potential sources of damage. Roof underlayment serves as a critical line of defense that enhances the performance and lifespan of your roof.

The Purpose of Roof Underlayment

Waterproofing: One of the primary functions of roof underlayment is to prevent water from seeping into the roof structure. Even if your roof shingles or tiles are damaged or blown away during a storm, the underlayment acts as a secondary barrier against rain, snow, and ice, keeping your home dry and free from water damage.

Protection from Moisture: In addition to preventing water infiltration, roof underlayment also helps manage moisture vapor within your attic and roof structure. This moisture management prevents mold and mildew growth and maintains a healthy living environment.

Temperature Regulation: Roof underlayment can also help regulate temperature by acting as an insulating layer. It can reduce heat transfer from the roof to the attic during hot summer months and minimize heat loss in colder seasons, improving overall energy efficiency.

Protection During Roof Installation: During the roof installation process, the underlayment offers a temporary layer of protection for your home until the final roofing material is installed. This safeguards your property from potential damage while the roof is being replaced or repaired.

Types of Roof Underlayment

Several types of roof underlayment materials are available, each with its own set of advantages and applications. The two primary categories of underlayment are:

Asphalt-Saturated Felt: Asphalt-saturated felt, also known as roofing felt or tar paper, is one of the most common types of underlayment. It consists of a base material, such as paper or fiberglass, saturated with asphalt. This type of underlayment is relatively inexpensive and provides good water resistance. However, it may deteriorate over time due to exposure to UV rays.

Synthetic Underlayment: Synthetic underlayment is a more modern alternative to traditional felt. It is made from polyethylene or polypropylene and is highly resistant to moisture, UV rays, and damage from mold or mildew. Synthetic underlayment is often preferred for its durability and long lifespan.

Installation of Roof Underlayment

Proper installation of roof underlayment is crucial to its effectiveness. Here are the general steps involved in installing roof underlayment:

Clean the Roof Deck: Before installing the underlayment, ensure that the roof deck is clean, dry, and free from debris. Any protruding nails or sharp objects should be removed or properly secured.

Start at the Bottom: Begin installing the underlayment at the eaves (bottom edge of the roof) and work your way up. Overlap each row of underlayment to ensure that water is directed downward and away from the roof deck.

Secure the Underlayment: Use roofing nails or staples to secure the underlayment to the roof deck. Follow the manufacturer’s guidelines for nail spacing and placement.

Proper Flashing: Pay special attention to flashing around roof penetrations, such as chimneys, vents, and skylights. Properly seal these areas with flashing to prevent water infiltration.

Overlap and Sealing: Ensure that each sheet or roll of underlayment overlaps the previous one by a few inches. Seal the seams with roofing cement or adhesive to create a watertight barrier.

Valleys and Edges: Take extra care when installing underlayment in roof valleys and along the edges. These areas are more susceptible to leaks, so ensure that they are well protected.

Maintenance and Inspection

Maintenance and Inspection

Once your roof underlayment is installed, it’s essential to perform regular maintenance and inspections to ensure its continued effectiveness. Here are some tips for maintaining your roof underlayment:

Visual Inspections: Periodically inspect your roof from the ground or hire a professional to check for any visible damage or signs of wear and tear.

Gutter Maintenance: Keep your gutters clean and free from debris to prevent water from backing up and potentially damaging the underlayment.

Trim Overhanging Branches: Trim any tree branches that hang over your roof to prevent them from causing physical damage or promoting moisture buildup.

Address Repairs Promptly: If you notice any issues with your roof, such as missing shingles or damaged flashing, address them promptly to prevent further damage to the underlayment.

Regular Roof Inspections: Consider scheduling regular roof inspections by a professional roofing contractor to catch any issues before they become major problems.


Roof underlayment may not be the most glamorous aspect of your roofing system, but it plays a vital role in protecting your home from the elements and ensuring the long-term durability of your roof. By understanding its purpose, choosing the right type of underlayment, and ensuring proper installation and maintenance, you can enjoy a watertight and resilient roof for years to come.

If you have any questions or need professional assistance with your roof underlayment or roofing needs, contact us at The Superior Group in New London, CT. Our experienced team of roofing experts is ready to assist you in keeping your home safe and secure.

In conclusion, investing in a quality roof underlayment and taking care of its maintenance needs is a crucial step in safeguarding your home from unpredictable weather conditions and ensuring the longevity of your roof. So, when it comes to roofing, remember that it’s not just about what you see on the surface; what’s underneath matters too.