You probably think your roof is just the shingles you see from the street, but there is a hidden layer working hard to protect your Silver Spring, MD, home from the elements. Understanding the various types of roof underlayment is crucial for a long-lasting and durable roof.
This protective barrier sits between the roof sheathing and your shingles. Think of it as the secret weapon against water damage and a key part of your roofing system. Knowing the main roof underlayment options helps you make the best choice for your house and budget.
What Is Roof Underlayment?
Roofing underlayment is a water-resistant or waterproof material installed directly onto your roof’s decking, also known as the roof sheathing. It’s your shingles’ backup, providing a second line of defense against rain, snow, and ice dams. Should a shingle blow off during high winds or a leak develop, this layer is what stops water from compromising your home’s structural integrity.
It also protects the roof deck while your new roof is being installed, especially if the project takes several days. A quality underlayment can add years to your roof’s life. This component is much more than just a thin sheet of material. It’s a critical part of your home’s defense system that sits beneath roofing materials.
The Main Roof Underlayment Types Explained
When you’re looking at roofing products, you’ll mainly encounter three basic types of underlayment. Each one has its own set of advantages and disadvantages.
Asphalt-Saturated Felt
This is one of the oldest types of underlayment, often called felt paper or tar paper, that roofing contractors have used for decades. This asphalt felt is made of a base mat, either paper or fiberglass, that has been soaked in asphalt for water resistance. You’ll typically find this felt underlayment in two standard weights: 15-pound and 30-pound.
The 30-pound felt is thicker, stronger, and offers more protection, though it costs more per square foot. For years, this asphalt-saturated felt was the standard material for almost every roofing job. It’s still a common choice today, particularly for lightweight projects or those on a strict budget.
The biggest plus for underlayment felt is its low cost. However, it’s prone to tearing during the roof installation process and can absorb water over time, leading to wrinkles and potential issues. Long-term exposure to UV rays before the roof covering is installed can also cause it to break down and become brittle.
Synthetic Underlayment
Synthetic roofing underlayment is a popular modern option. It’s made from polymers woven together, like polypropylene, which makes it incredibly strong and lightweight. A whole roll of synthetic material weighs much less than asphalt felt, making it easier and safer for a roofing contractor to handle on the roof.
Its main advantage is durability and how it repels water effectively. This material is very tear-resistant, holding up better against foot traffic and wind during installation. Many synthetic underlayments also feature a specialized upper surface that provides a secure walking surface for roofers, reducing the risk of slips and ladder trips.
Synthetic options do cost more than traditional felt paper, though the price difference is narrowing. A key consideration is that synthetics are not breathable, so your attic must have sufficient ventilation. Without it, moisture can become trapped, potentially leading to mold or rot in the roof deck.
Self-Adhered Underlayment
When you need the absolute best protection, you turn to self-adhered underlayment, which is made from rubberized asphalt. This premium product contains a high concentration of asphalt and rubber polymers for maximum flexibility and sealing power. Most types have an adhesive backing that bonds directly to the roof deck.
This creates a completely waterproof membrane across your roof. It’s the top choice for preventing leaks, especially in vulnerable areas like eaves, valleys, and around chimneys. It’s also an excellent defense in climates with heavy snow and ice because it protects against ice dams, a common cause of roof damage in cold weather.
The biggest drawback is the cost. This is the most expensive of the underlayment options. It’s also heavy and requires a skilled installation process, as the powerful adhesive makes it difficult to reposition. This is a material best left to experienced performance roofing professionals who can withstand high expectations.
Comparing Your Options Side-by-Side
Choosing the right material can feel challenging. Sometimes seeing the details laid out helps clarify which one fits your specific needs. This quick comparison should provide a clearer picture.
| Feature | Asphalt-Saturated Felt | Synthetic Underlayment | Self-Adhered Underlayment |
|---|---|---|---|
| Cost | Low | Medium | High |
| Durability | Fair | Excellent | Superior |
| Water Protection | Resistant | Very Resistant | Waterproof |
| Best For | Budget Projects | Most Homes | Harsh Climates |
Your decision depends on your top priorities. If budget is the main concern, asphalt felt is a functional choice. If you want a great blend of performance and value for your home, synthetic is likely the best option. For homes in areas with extreme weather, the extra cost of self-adhered underlayment provides valuable peace of mind.
Frequently Asked Questions About Roof Underlayment
Here are answers to some frequently asked questions about roofing underlayment.
Can you install a new roof layer over old underlayment?
This is generally not recommended. Old underlayment may be torn, brittle, or ineffective, and leaving it in place can hide existing roof damage on the sheathing beneath the roofing. A reputable roofing contractor will always remove the old layers.
Do you need to follow local building codes?
Absolutely. Local building codes often dictate the type of underlayment required for your area based on climate factors like wind speed and snowfall. Always consult local building regulations or a knowledgeable contractor.
Does my choice of underlayment affect roofing warranties?
Yes, it certainly can. Many shingle manufacturers require specific types or grades of underlayment to validate their warranties, so always check the requirements for your chosen roof shingles.
Final Thoughts
The layer beneath your shingles does important work protecting your home. Choosing between the available roof underlayment types depends on your budget, climate, and desired longevity for your roof. Asphalt felt works for a basic roof, synthetic offers a fantastic upgrade, and self-adhered underlayment provides the ultimate defense.
Consult with a professional roofer about their recommendation. They will have direct experience with how these different roof underlayment types perform in your specific area. Making the right choice for this crucial roof layer helps you get a strong, reliable, and weather-resistant roof that lasts for many years to come.
