How To Install Synthetic Underlayment On Roof? (9 Steps)

When it comes to roofing, one of the lesser-known but critical components is the underlayment. Often overlooked by homeowners, underlayment plays a vital role in ensuring your roof not only protects your home but also lasts as long as possible.

In recent years, synthetic underlayment has gained popularity due to its superior performance and durability compared to traditional materials. In this post, we will explore:

• What synthetic underlayment is
• Its pros and cons
• How it compares to other types of underlayment
• The cost of installation
• Its longevity
• Whether you can install new underlayment without a full roof replacement

What is Synthetic Underlayment?

Synthetic underlayment is a type of roofing underlayment made from polymers, such as polypropylene or polyethylene. It serves as a protective layer between the roof deck and the final roofing material (such as shingles, tiles, or metal roofing). Its primary function is to provide an additional layer of protection against moisture, wind, and other environmental factors that can damage your roof’s structural integrity.

Unlike traditional underlayments made from materials like asphalt-saturated felt, synthetic underlayments are designed to be lightweight, durable, and resistant to water, mold, and UV rays. They come in rolls and are typically installed directly onto the roof deck before the final roofing material is applied.

✅ Pros of Synthetic Underlayment

When considering synthetic underlayment, homeowners can benefit from several significant advantages over traditional options.

• Durability: Synthetic underlayment is known for its exceptional strength and durability. It can withstand harsh weather conditions, including heavy rain, high winds, and extreme temperatures, far better than traditional felt underlayment.
• Water Resistance: One of the most significant advantages of synthetic underlayment is its superior water resistance. It acts as a barrier to prevent water from seeping into the roof deck, reducing the risk of leaks and water damage inside your home.
• Lightweight: Synthetic underlayment is much lighter than traditional felt, which makes it easier for contractors to handle and install. This can also contribute to faster installation times and potentially lower labor costs.
• Mold and Mildew Resistance: Because synthetic underlayment is not organic, it does not provide a food source for mold and mildew, making it resistant to these common issues associated with traditional roofing materials.
• UV Protection: Many synthetic underlayments offer UV ray resistance, which is beneficial if your roofing material installation is delayed. This feature helps protect the roof deck and extends the life of your underlayment.
• Tear Resistance: Synthetic underlayment is less prone to tearing compared to felt, which can be easily damaged during installation or in high winds.
• Longer Lifespan: Generally, synthetic underlayments tend to last longer than traditional felt options, providing a more reliable roofing solution over time.

❌Cons of Synthetic Underlayment

While synthetic underlayment offers numerous benefits, it is important for homeowners to also consider potential drawbacks before making a decision.

• Cost: Synthetic underlayment tends to be more expensive than felt underlayment. However, it’s essential to consider the long-term benefits and durability that synthetic options provide, which can offset the initial investment.
• Slick Surface: Some synthetic underlayments can have a slick surface, which can make them more challenging to walk on during installation. Many manufacturers compensate for this by adding a textured surface to improve traction.
• Installation: While synthetic underlayment is relatively easy to install, it requires precise installation techniques to ensure maximum effectiveness. Hiring professional, experienced roofers is recommended to avoid any issues.

Comparing Synthetic Underlayment to Other Types of Underlayment

In this section, we will undertake a detailed comparison of synthetic underlayment with traditional felt and other contemporary underlayments to assist you in making an informed choice for your roofing needs.

Asphalt-Saturated Felt

• Durability: Felt underlayment is less durable compared to synthetic. It can become brittle over time and is susceptible to water damage.
• Water Resistance: Felt offers basic water resistance but can absorb water if exposed for prolonged periods, potentially leading to roof deck damage.
• Installation: Felt is heavier and more cumbersome to install than synthetic underlayment.
• Cost: Felt is generally cheaper upfront but may require more frequent replacement.

Rubberized Asphalt

• Durability: Rubberized asphalt underlayment is quite durable and offers excellent waterproofing but is typically used in specific scenarios like low-slope roofs or areas prone to ice dams.
• Water Resistance: Offers superior water resistance due to its adhesive properties.
• Cost: Typically more expensive than both felt and synthetic underlayments.

Non-Bitumen Synthetic

• This is another category of synthetic underlayment, similar in material to the polymer-based underlayments discussed.
• Offers flexibility, UV protection, and is lightweight.

How to Install Synthetic Underlayment: 9 Key Steps

Installing synthetic underlayment is a process that can significantly enhance the longevity and performance of your roof, but it requires precision and attention to detail. Below are the steps to guide you through the installation:

1) Prepare the Roof Deck:

Ensure that the roof deck is clean, dry, and free of any debris or protruding nails. This step is crucial to create a smooth surface for the underlayment which will prevent potential damage or tears.

2) Safety First:

Prioritize your safety by using the necessary equipment like safety harnesses and sturdy ladders. Wearing slip-resistant shoes and ensuring a stable work environment can prevent accidents, especially on sloped roofs.

3) Install the Drip Edge:

Begin by installing a metal drip edge along the eaves of the roof. This acts as a safeguard against water damage by directing water away from the fascia.

4) Position the Underlayment:

Start at the lowest point of the roof and roll out the synthetic underlayment parallel to the eaves. Make sure the material is flat and wrinkle-free to avoid any issues during shingle installation.

5) Secure the Underlayment:

Use roofing nails or staples to secure the underlayment. Fasten it adequately according to the manufacturer’s guidelines, which typically recommend spacing nails at every 6-12 inches along the edges and 24 inches in the field.

6) Overlap Rows:

When starting a new row, overlap each subsequent layer by at least 4 inches to ensure comprehensive coverage and prevent water infiltration. This is critical for maintaining the moisture-resistant barrier.

7) Work Around Protrusions:

Carefully cut the underlayment around any roof penetrations, such as vents, chimneys, or skylights. Utilize chalk lines to maintain consistent alignment and leverage adhesive underlayment strips or tapes to seal around these complex areas.

8) Install the Drip Edge on the Rakes:

Once the underlayment is in place, install metal drip edges along the rakes of the roof to ensure full protection against wind-driven rain.

9) Final Inspection:

Inspect the entire surface to confirm that the underlayment is securely fastened and free of damage. Address any loose areas or wrinkles promptly to maintain roof integrity.

By ensuring each of these steps is followed carefully, you’ll set a solid foundation for your roofing material, maximizing the life and reliability of both the underlayment and the roof itself. Considering its enhanced benefits, investing in a professional roofer is often a worthwhile consideration to ensure the job is executed with precision and professionalism.

Cost to Install Synthetic Underlayment

The cost to install synthetic underlayment varies based on several factors, including the size of your roof, the particular brand or type of synthetic underlayment chosen, local labor rates, and the complexity of your roof’s design. On average, homeowners can expect to pay between $0.75 and $1.50 per square foot for synthetic underlayment materials. Labor costs will add to this estimate, with total installation costs ranging from $1.50 to $3.00 per square foot.

While synthetic underlayment may cost more than traditional felt options, its durability and longevity can lead to savings in the long run by reducing the need for repairs and replacements.

How Long Does Synthetic Underlayment Last?

Synthetic underlayment can last anywhere from 20 to 40 years, depending on the brand, quality, and installation conditions. Factors such as climate, exposure to sunlight, and the quality of installation will all influence its lifespan. Properly installed synthetic underlayment offers homeowners peace of mind, knowing their roof has an extra layer of protection that can last for decades.

Can You Install New Underlayment Without a Full Roof Replacement?

In some cases, it may be possible to replace underlayment without doing a full roof replacement, but this depends on the condition of your existing roof materials. If the roofing material (shingles, tiles, etc.) is still in good condition, it can be carefully removed and reinstalled once the new synthetic underlayment is in place. However, if the roofing material is nearing the end of its life or has sustained damage, a full roof replacement is often more cost-effective and efficient.

It’s essential to have a professional roofing contractor assess your roof’s condition before making a decision. They can provide expert guidance on whether replacing the underlayment alone or opting for a complete roof replacement is best for your situation.

Your Go-To Roofing Contractors

Synthetic underlayment offers homeowners a robust, durable, and reliable solution for roof protection. Its numerous benefits, such as enhanced water resistance, longevity, and improved tear strength, make it an attractive choice over traditional felt underlayment. While the initial cost may be higher, the long-term savings and peace of mind it provides are invaluable.

If you’re considering installing synthetic underlayment or have questions about your roof’s condition, contact our team at Roof Medic. With expert advice and quality service, we’ll help you make the best choice for your home’s protection. Don’t hesitate to reach out and learn more about how synthetic underlayment can enhance your roof’s performance.