When building or repairing a roof, the materials beneath the surface are just as important as the outer layer. Roofing felt and underlayment are two key components that are crucial in protecting your roof from water damage, weather elements, and structural wear over time. So, what sets these two materials apart, and how can you determine which one is best suited for your project?
In this blog, we’ll explore the distinct characteristics, benefits, and applications of roofing felt and underlayment, providing you with the knowledge to make an informed choice for your roofing needs. Whether you’re a homeowner tackling a renovation or a contractor managing a large-scale project, understanding these materials is crucial for achieving a strong and long-lasting roof.
What is Roofing Felt?
Roofing felt, commonly referred to as tar paper, is a traditional material used in roofing systems to create a protective layer between the roof deck and the outer roofing materials, such as shingles or tiles.
Key Features of Roofing Felt
Material Composition:
Roofing felt is made from organic or synthetic fibres, typically saturated with asphalt to enhance its water-resistant properties.
Durability:
While effective, roofing felt may be less durable than modern alternatives, particularly in extreme weather conditions.
Water Resistance:
It provides a basic level of water resistance, preventing water from penetrating the roof deck in case of leaks or damage to the top layer.
Affordability:
Roofing felt is a cost-effective option for basic roofing projects.
Benefits of Roofing Felt
- Budget-Friendly: Roofing felt is an affordable option, making it ideal for homeowners working within a budget.
- Easy to Use: Its lightweight design makes it simple to handle and install.
- Basic Protection: Offers a reliable barrier against water infiltration during initial roof construction.
What is Roofing Underlayment?
Underlayment is a broader term encompassing various materials placed between the roof deck and the outer roofing layer. It serves as an extra layer of protection, shielding the roof deck from water penetration, wind, and debris.
Key Features of Roofing Underlayment
Durability and Longevity:
Modern underlayment options are designed to withstand harsh weather and last for the roof’s lifespan.
Enhanced Protection:
Underlayment offers better resistance to water, wind, and UV exposure than roofing felt.
Price Range:
Although more expensive than roofing felt, underlayment provides greater long-term value due to its durability.
Types of Underlayment:
- Synthetic Underlayment: Made from durable materials like polypropylene or polyethylene, offering enhanced strength and water resistance.
- Rubberised Asphalt Underlayment: Contains asphalt and rubber polymers, providing superior waterproofing.
Benefits of Roofing Underlayment
- Enhanced Weather Resistance: Synthetic underlayment provides superior protection against extreme weather conditions.
- Durability: Engineered to match the lifespan of the roofing materials, minimising the need for frequent replacements.
- Improved Safety: Slip-resistant surfaces on some underlayment options make installation safer for roofers.
Comparing Roofing Felt and Underlayment
Here’s a direct comparison to emphasise the key differences:
| Feature | Roofing Felt | Roofing Underlayment |
| Material Composition | Organic or synthetic fibres with asphalt | Synthetic polymers or rubberised asphalt |
| Durability | Moderate | High |
| Water Resistance | Basic | Superior |
| UV Resistance | Limited | Excellent |
| Ease of Installation | Relatively simple | Slightly more complex |
| Cost | Affordable | Higher upfront cost |
Uses and Applications
Roofing Felt Applications:
- Ideal for smaller residential projects.
- Often used in traditional roofing systems.
- Suitable for regions with mild weather conditions.
Underlayment Applications:
- Preferred for larger or commercial projects.
- Commonly used in modern roofing systems, particularly with metal or tile roofs.
- Essential in areas with heavy rain, snow, or high winds.
Installation Considerations
Roofing Felt:
- Easier to install and suitable for DIY enthusiasts.
- Requires careful alignment to avoid overlaps and gaps.
Underlayment:
- Typically installed by professionals due to its heavier weight and specialised application methods.
- Requires precise installation to maximise its protective benefits.
Choosing the Right Material for Your Roof
The choice between roofing felt and underlayment depends on several factors:
1. Budget:
Roofing felt is more economical upfront, while underlayment offers better long-term value.
2. Weather Conditions:
Underlayment is preferred for areas with severe weather conditions thanks to its superior durability and water resistance.
3. Type of Roofing Material:
Metal and tile roofs often require synthetic underlayment for optimal performance.
4. Project Size and Scope:
Smaller residential projects can use roofing felt, while larger or commercial projects benefit from synthetic underlayment.
Why Roofing Felt is Still Relevant
Despite the rise of synthetic underlayment, roofing felt remains a popular choice for traditional roofing projects. Its affordability and straightforward installation make it a viable option for homeowners seeking a reliable yet economical solution.
The Future of Roofing Underlayment
Advancements in technology have led to the development of underlayment materials with exceptional durability, weather resistance, and eco-friendly features. These materials are gradually becoming the industry standard for both residential and commercial roofing projects.
Conclusion
Both roofing felt, and underlayment plays vital roles in protecting a roof and ensuring its longevity. While roofing felt is a traditional and budget-friendly option, modern underlayment offers superior performance and durability, making it the preferred choice for most roofing systems today.
When deciding between the two, consider your budget, regional weather patterns, and the specific needs of your roofing project. Whether you’re a homeowner or a contractor, understanding the distinctions between these materials will enable you to make a well-informed choice and ensure a strong, long-lasting roof.