Most people associate roofs with metal roofing or shingles. What many people don’t know is that there’s an additional layer of protection on top of your roof deck and underneath the roof covering. This protects your home from moisture damage. It’s called roofing underneath.
Learn more about this crucial component of your roof’s structure.
What is Roofing Underlayment?
The roofing underlayment, also known as roof sheathing or roof deck, is the layer between the shingles, roof sheathing, or roof deck. It is usually plywood or OSB. It is installed directly on the roof deck, providing a second layer of protection against the elements including rain, snow, and wind.
Types of roofing underlayment
There are two types of roofing underlayment.
Felt
Synthetic
Every product has its advantages and disadvantages. The type of product you choose will depend on where you live, the roofing materials you use, your budget, and any suggestions from your roofing contractor.
Felt Roofing Underlayment
Felt roofing is the oldest type of roofing underlayment. It is made of saturating paper with asphalt or fiberglass mat.
There are two types of felt roofing underlayment: No.15 and No. 30. 30 felt. Comparable to No. 15 felt No. 30 felt is thicker and stronger than 15 felt. It may also be less susceptible to being ripped off during installation.
Pros
The primary advantage of using felt roofing underlayment is its cost. Felt roofing underlayment is often less expensive than synthetic, making it a popular choice for budget-conscious homeowners.
Cons
There are many disadvantages to using felt roofing underlayment. Traditional felt roofing underlayment can’t be left out for more than a few hours. The heat can cause the material to dry out and leach oils. This could impact the felt’s ability to protect against moisture.
Another drawback to felt underlayment is:
High winds and the strain of installation can cause tearing.
The mat can absorb moisture and wrinkle the felt making it difficult for the shingles not to lie flat if they are exposed to moisture. To ensure maximum protection, shingles should always be installed as soon as the felt roofing underlayment has been installed.
Felt underlayment is also heavier, making it more difficult for roofing contractors and roofers to lift it up onto a roof.
It can also be slippery, making it difficult to install.
Also, the weight of the material means that there is less material per roll. This results in more seams than a single course that has no laps.
Warranty and Underlayment for Felt Roofing
Felt underlayment may be installed to prevent you from receiving manufacturer’s warranties. This may lead to synthetic underlayment being required.
Synthetic Roofing Underlayment
Many roofers choose to use synthetic roofing underlayment for enhanced water resistance and protection from the elements. These products are often made of long-lasting polymers that provide greater strength and durability. This underlayment is usually water-resistant and, when installed correctly, offers greater protection against the elements than felt.
Different manufacturers make synthetic roofing underlayment materials differently. This means that they may have different performance levels. Talk to a trusted contractor to help you choose the best roofing material to protect your home.
Pros
Synthetic roof underlayment is better than felt for four reasons. Synthetic roofing underlayment has the following advantages over felt:
Tough
Installation is quick
Secure
Repels water
Synthetic underlayment is durable and tough construction that can withstand a lot more than felt.
The synthetic roof underlayment can be very durable. It is extremely durable and won’t tear.
The synthetic underlayment is also resistant to boots traffic. This is especially important for roofing contractors who are walking on the surface while it is being installed. Owens Corning Roofing calls this “use after abuse”. The product can still perform as intended even after being subject to a lot of abuse during installation.
Also, synthetic roofing underlayment tends to be:
Lighter* – Some cases up to four times lighter
It is fast to install – Synthetic roofing underlayment has a greater material density than felt. This means that your roofers will need to make fewer trips up the ladder, which may result in them spending less time and possibly making the job go faster. A typical 2700-square-foot home may require three rolls of a synthetic underlayment, while No.30 felt would take 14 rolls to cover the same area.
Safe – Synthetic roofing underlayments are also safer for workers. Many synthetic roofing underlayments, such as those made by Owens Corning have slip-resistant surfaces that allow for better walking. It is also marked with overlap guides and indicators that indicate where fasteners should go, which helps to ensure consistency and accuracy in installation.
Moisture-resistant: Synthetic roofing underlayments repel water. Unlike felt products, which tend to absorb water. This is especially important for homeowners who are concerned about moisture infiltration.
Synthetic underlayment is made from plastic and has a higher resistance to mold growth than felt.
Cons
Although synthetic roofing underlayment can be competitively priced, it is still more expensive than felt. However, the upfront investment in better-quality roofing materials could help you save money later. It’s hard to beat the comfort of knowing your roof is adequately protected from water.
The right underlayment for your roof
There are many things to consider when choosing the right type of underlayment for your project, whether it’s new construction or a re-roofing. Synthetic roofing underlayment offers many benefits over felt and can be a good investment to protect your roof from moisture and water infiltration.
Contact us anytime for a free roof inspection, or estimate on your roofing project!
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