Is Roofing Tar Paper Waterproof and How It Protects Your Roof
Roofing tar paper, also known as felt paper, is widely used in residential and commercial roofing as an underlayment. Many homeowners and builders wonder, is roofing tar paper waterproof? While tar paper offers some water resistance, its main function is to act as a protective barrier against moisture and weather elements. Understanding its properties, uses, and limitations is key to ensuring your roof’s durability and performance.
| Feature | Description |
|---|---|
| Material | Organic or fiberglass felt saturated with asphalt or tar |
| Water Resistance | Water-resistant but not fully waterproof |
| Primary Purpose | Protect roof decking from moisture, secondary weather barrier |
| Installation Location | Under shingles or other roofing materials |
| Types | 15-pound and 30-pound tar paper variants |
What Is Roofing Tar Paper?
Roofing tar paper is a construction material traditionally made from organic felt or fiberglass mats saturated with asphalt or tar. This saturation process makes the felt water-resistant and more durable, serving as a base layer during roofing installation. It is rolled out onto the roof deck before shingles or other roofing materials are applied.
There are generally two types of tar paper based on weight: 15-pound and 30-pound. The higher the number, the thicker and more durable the material. 30-pound tar paper is more commonly used because it provides better protection.
Is Roofing Tar Paper Waterproof or Water-Resistant?
Roofing tar paper is primarily water-resistant, not completely waterproof. This means it repels water to a certain extent but should not be relied upon to keep water out indefinitely if exposed to prolonged water contact.
The asphalt or tar saturation creates a barrier that helps prevent moisture from penetrating the underlying roof decking, but tar paper is not impervious to water seepage. For this reason, it acts as a secondary line of defense, protecting the roof structure from minor leaks and condensation that may bypass the primary roofing material.
How Roofing Tar Paper Functions in Moisture Protection
Tar paper serves several essential functions in roofing systems:
- Temporary Weather Protection: During roofing installation, tar paper shields the roof deck from rain and wind.
- Moisture Barrier: It limits the amount of moisture reaching the roof deck, reducing the risk of wood rot, mold, and mildew.
- Improved Roof Lifespan: By protecting decking and underlayers, it contributes to the longevity of the entire roofing system.
Despite these protections, tar paper works in conjunction with shingles or other roofing materials that provide the primary waterproof seal.
Types of Roofing Underlayments: Tar Paper vs. Synthetic Alternatives
While traditional tar paper is widely used, many builders now opt for synthetic roofing underlayments. These provide enhanced waterproofing and durability.
| Feature | Tar Paper | Synthetic Underlayment |
|---|---|---|
| Material | Organic felt or fiberglass saturated with tar/asphalt | Polypropylene or polyester fabric |
| Waterproofing | Water-resistant, not fully waterproof | Highly waterproof |
| Durability | Prone to tearing and degradation | Stronger, UV resistant |
| Cost | Lower cost | Higher cost |
Common Uses of Roofing Tar Paper
Tar paper remains common in the roofing industry for several reasons:
- Traditional choice for many roof types and designs
- Affordable underlayment in new construction or reroofing projects
- Easy to apply and compatible with most shingle types
- Provides a breathable layer that helps with ventilation and moisture control
Limitations of Roofing Tar Paper
Despite its benefits, tar paper has limitations, especially in its waterproofing capability:
- Not fully waterproof: It does not stop water intrusion during heavy rain or standing water.
- Susceptible to tearing: It can easily tear during installation or under strong winds.
- Degrades over time: Prolonged exposure to sun and weather causes the material to break down.
- Requires proper installation: Overlapping seams and secure fastening are critical to maximize effectiveness.
Tips for Proper Installation of Tar Paper
Correct installation of roofing tar paper is vital for maximizing its protective qualities. Follow these tips:
- Start from the bottom: Roll the tar paper horizontally starting at the eaves with overlaps of at least 2 inches.
- Secure well: Use roofing nails or staples to fasten the tar paper firmly, avoiding wrinkles or bubbles.
- Overlap appropriately: Ensure vertical overlaps are about 4 inches to prevent water seepage.
- Check for damage: Replace any torn or compromised sections immediately.
When to Consider Waterproof Alternatives
In areas prone to heavy rainfall, ice dams, or where roof leaks are a frequent problem, upgrading to more waterproof underlayments may be beneficial. Synthetic desiccated membranes or peel-and-stick roofing underlayments offer superior water barrier protection.
Areas to consider waterproof solutions include:
- Hurricane or tropical storm-prone regions
- Cold climates with frequent freeze-thaw cycles
- Low-slope roofs where water runoff is slower
- Rooftops with complex designs and multiple valleys
Maintaining the Effectiveness of Roofing Tar Paper
Maintenance plays a crucial role in extending tar paper’s performance:
- Inspect roofs regularly for damaged shingles that can expose tar paper
- Replace worn or torn tar paper during reroofing projects
- Ensure gutters and downspouts are clean to prevent water backup
Summary
Roofing tar paper provides essential water resistance and protection to roof decking but is not completely waterproof. It serves as an effective secondary barrier when properly installed under shingles or other roofing materials. For enhanced waterproofing, especially in extreme weather conditions, synthetic or peel-and-stick membranes are preferred. Understanding the capabilities and limitations of tar paper helps homeowners and contractors make informed roofing decisions.