Roofing is a complex process that involves numerous elements to ensure a durable, long-lasting, and water-resistant cover for our homes. One vital component that often gets overlooked is underlayment. While shingles or tiles make up the outer layer that we see, underlayment is the unseen hero that provides an extra layer of protection against the elements.
In this post, we’ll delve into the role of underlayment, its various types, and some tips on installation.
1. The Basic Function and Importance of Underlayment
- Protection Against the Elements: Whether you’re using metal roofing, tiles, or asphalt shingles, an underlayment acts as a secondary barrier against rain, snow, and wind. Especially in the case of metal roofing, an underlayment can prevent condensation and potential water damage.
- Provides a Smooth Surface: It helps to level out the roof deck ensuring the outer layer of shingles or tiles lies flat. A smoother application means a neater appearance and more efficient protection.
- Enhances Fire Resistance: Many types of underlayment are fire-resistant, adding an extra safety feature to homes.
2. Types of Underlayment
- Asphalt-saturated felt: Once the most common type, this water-resistant underlayment is now being phased out for more synthetic materials but is still in use for specific applications.
- Rubberized asphalt: This is more expensive but offers a higher level of waterproofing. It contains higher amounts of asphalt and rubber polymers, ensuring better adherence to the roof deck.
- Synthetic underlayment: Made of polypropylene or polyester, it is lighter, stronger, and more resistant to water than felt. Its non-skid quality also makes it safer for installers.
3. Factors Influencing the Choice of Underlayment
- Climate: In areas with heavy rainfall or snow, waterproof underlayment like rubberized asphalt may be preferred.
- Roofing Material: Metal roofing, for instance, might require a specific type of underlayment that caters to condensation issues.
- Slope of the roof: Low-sloped roofs might demand a higher waterproofing grade than steeper slopes.
- Local Building Codes: Always ensure that your choice aligns with the requirements set by local authorities.
4. Installation Tips
- Start at the Bottom: Begin installing from the bottom edge of the roof and work your way upwards. This ensures that water flows over the seams, not into them.
- Overlap Layers: By overlapping the underlayment layers, you guarantee that water can’t seep through the seams. A typical overlap is around 2 inches for horizontally laid sheets and 4 inches for vertically laid ones.
- Flat and Smooth: Ensure that the underlayment lies flat and smooth on the roof deck. Wrinkles or bubbles can cause issues with the top layer of shingles or tiles.
- Secure Firmly: Depending on the type of underlayment and the manufacturer’s recommendations, use roofing nails or staples to secure it. Ensure it’s taut and anchored firmly to avoid wind damage.
5. When to Replace Underlayment
Underlayment, just like any roofing material, has a lifespan. If you’re replacing your roof, it’s usually a good idea to replace the underlayment too, even if it appears in decent condition.
Some signs that your underlayment might need replacing include:
- Leaks or water stains in the attic.
- Visible damage or wear when replacing shingles or tiles.
- Consistent dampness or mold growth.
Roofing is about more than just the top layer that we see. It’s a system that works together to protect our homes. While underlayment may remain hidden, its role is crucial. Whether it’s aiding in waterproofing, providing a smooth base for shingles, or enhancing the fire resistance of a home, underlayment is a fundamental component of a well-structured roof.
By understanding its purpose, types, and installation nuances, homeowners can ensure they’re making informed decisions about their roofing choices, leading to safer and more durable homes.