The roof underlayment is one of the most important layers on your roof. It is an even and smooth layer for your final roofing material and protects the underlying materials like decking, joist, truss, etc.
At RST Roofing and Renovations, LLC, we are your trusted roofing company serving Atlanta and the surrounding areas of Georgia. In today’s article, we will walk you through the construction, types, cost, and importance of roof underlayment.
To discuss your project with professional roofing experts, feel free to call us today at (404) 548-8901.
What Is Roof Underlayment?
As we have already said, roof underlayment is a very important component in any roofing system. It serves as a protective barrier between the roofing material and the structural components beneath (such as the roof deck).
Roof underlayment helps keep your roof waterproof, energy-efficient, and durable against harsh weather conditions.
Roofing underlayments are made using asphalt-saturated felt, rubberized asphalt, or synthetic materials. These materials provide various levels of waterproofing, flexibility, and durability, based on your roofing needs.
The installation of roof underlayment directly onto the roof deck ensures your home is protected against moisture, wind-driven rain, and thermal fluctuations.
Is A Roof Underlayment Necessary?
While yes, a roofing underlayment is necessary, it is technically possible to install a roof without it. But remember that doing this generally comes with consequences.
Without an underlayment, your roof is more susceptible to water damage, leaks, and mold growth. Also, it lacks an additional layer of insulation that helps regulate indoor temperatures.
Additionally, many building codes and roofing warranties require underlayment for compliance. So, skipping this step may result in structural problems and voided warranties.
What Are the Different Types of Roof Underlayment?
Now, as you know what roof underlayment is and why it’s important, you should also know about the types available.
There are a few types of roof underlayments on the market, and to choose the best fit for your roof, you should be aware of the characteristics of each.
Here, we will quickly go over all the common types of roof underlayments.
#1 Felt Underlayment
Lifespan: 10 to 20 years
Construction: Made from organic or fiberglass mat saturated with asphalt.
Suitability: Best for budget-friendly roofing projects and moderate climates.
Felt underlayment, also known as asphalt-saturated felt, has been widely used for years due to its affordability and ease of installation. It provides a water-resistant layer that helps prevent moisture penetration, but it is not entirely waterproof.
You can find felt underlayment in two common thicknesses: #15 and #30 felt.
The #30 variant is more durable and tear-resistant, making it a better choice for areas prone to extreme weather conditions.
However, it is important to know that felt underlayment can absorb moisture over time. This may result in wrinkling or deterioration.
#2 Synthetic Roof Underlayment
Lifespan: 25 to 50 years
Construction: Made from polypropylene or polyethylene polymers.
Suitability: Best for all types of roofing materials (especially metal and tile roofs).
Synthetic roof underlayment has gained popularity because of its durability and performance. Unlike felt underlayment, synthetic roof underlayment is lightweight, tear-resistant, and does not absorb moisture. This reduces the risk of wrinkling.
It also provides really nice UV resistance, allowing it to remain exposed for longer periods before the final roofing material is installed.
Plus, a synthetic underlayment provides nice slip resistance, which improves safety for roofers during installation. It is particularly recommended for steep-slope roofs and metal roofing systems because of its high-temperature tolerance.
#3 Rubberized Asphalt Underlayment
Lifespan: 30 to 50 years
Construction: Asphalt modified with rubber polymers for enhanced flexibility.
Suitability: Recommended for areas with extreme weather conditions and high-temperature roofs.
Rubberized asphalt underlayment is one of the most advanced and durable roofing underlayment options that you will find on the market. It consists of asphalt infused with rubber polymers, which improves its flexibility and self-sealing properties around nails and fasteners.
This roofing underlayment is highly resistant to temperature fluctuations, making it an excellent choice for regions that experience extreme heat or cold.
It can also withstand prolonged UV exposure and can be used for projects with extended installation times.
Because of its high cost, rubberized asphalt underlayment is mostly used in premium roofing projects or areas with extreme weather conditions.
#4 Ice and Water Shields
Lifespan: 20 to 30 years
Construction: Modified bitumen
Suitability: Very important in areas with heavy snow and rainy weather.
Ice and water shields are another important waterproof membrane that protects your roof from potential leaks.
It comes in three types: granular (the least expensive), smooth (most flexible), and high-heat (best for metal roofs). Some high-heat options come with a cotton-fiber backing, which prevents it from sticking to the roofing material during extreme temperatures.
This underlayment is usually not used across the entire roof, and instead is installed on the most vulnerable areas of your roof, like valleys, around penetrations, and along the roof edges. This added protection keeps water out of the roof structure during severe storms.
What Are The Common Signs Of A Damaged Roof Underlayment?
Because underlayment is a hidden component of your roof, it is important to know the common signs of damage. Below, we will go over the signs that indicate it’s time to get your roof underlayment checked by a professional.
#1 Water Leaks
Starting with a most alarming sign, persistent leaks in your ceiling or attic are a strong indication that your underlayment has failed. Water seeping through compromised underlayment can lead to costly repairs and mold issues.
#2 Mold or Mildew Growth
Excessive moisture retention can create an environment where mold and mildew thrive. If you see mold inside your attic or on your ceiling, your underlayment might not be doing its job properly.
#3 Increased Energy Bills
A damaged underlayment can impact your home’s insulation, forcing your HVAC system to work harder. If your energy bills have increased unexpectedly, it could be due to deteriorating underlayment, reducing your home’s energy efficiency.
#4 Aging Roof
Roof underlayment has a limited lifespan, and as it ages, it becomes less effective. If your roof is over 20 years old and has not been replaced, it’s wise to have it inspected to ensure the underlayment is still in good condition.
How to Install Roof Underlayment
For a successful underlayment installation, it is very important to understand the steps involved. However, professional installation is always recommended over DIY.
Step 1: Prepare the Roof Deck
Before starting, make sure that the roof deck is completely dry and free of dirt, dust, or debris. Any nails or protrusions should be removed to create a smooth surface.
If there are damaged or rotten sections of the deck, they should be replaced to create a stable foundation for the underlayment.
Step 2: Install the Drip Edge
Attach the drip edge along the eaves to prevent water from going under the roofing materials. This metal flashing protects the roof edge, which reduces the risk of moisture damage.
Secure the drip edge with roofing nails, ensuring proper overlap at the corners.
Step 3: Roll Out the Underlayment
Starting from the lowest point of the roof, roll out the underlayment horizontally across the roof deck.
Each row should overlap the previous one by at least 2 inches for steep-slope roofs and 19 inches for low-slope roofs.
Your roofer must make sure that the underlayment lays flat without wrinkles to prevent future issues with water pooling.
Step 4: Secure the Underlayment
Use cap nails or staples to fasten the underlayment, spacing them according to manufacturer recommendations.
Generally, fasteners should be placed along the edges and in the center of each roll. Avoid overdriving nails, as this could damage the material and reduce its effectiveness.
Step 5: Overlap and Seal
Proper overlapping is necessary to create a completely waterproof layer. Follow the underlayment manufacturer’s guidelines for overlap width.
In high-wind areas and on particularly vulnerable sections of your roof (like valleys and ridges), consider using roofing tape or an adhesive seal to reinforce the underlayment.
Step 6: Install the Final Roofing Material
Once the underlayment is securely in place, proceed with installing the final roofing material, whether it be shingles, metal panels, or tiles.
Ensure that the roofing material aligns with the underlayment for maximum protection and longevity.
Do Roof Underlayments Need Professional Installation?
While you can try installing your roof yourself, it is best to leave it to professionals. This is because they have the right experience, expertise, and knowledge to handle the job.
Your roof needs a very proper installation to maintain its performance and lifespan. Even a minor installation problem can result in bigger problems down the line.
Get High-Quality Roof Installation In Georgia
At RST Roofing and Renovations, LLC, we are your local roofing company serving Atlanta and the surrounding areas of Georgia. Our team understands the importance of a well-installed roof.
We only use the right practices and industry-certified materials to make sure that roofs not only look nice but also perform well for many years to come.
To schedule a non-obligation discussion with our professionals, contact us at (404) 548-8901.
