Rolled Roofing Over Shingles

Rolled Roofing Over Shingles: A Practical Guide for Homeowners

When it comes to roofing repairs, many homeowners consider applying rolled roofing over existing shingles as a cost-effective method. This approach can prolong the life of the roof and reduce labor costs, but it requires careful planning and understanding of roofing principles. Rolled roofing, also known as roll roofing, is a material that comes in large rolls and is typically used for low-slope roofs. This article explores the feasibility, benefits, drawbacks, and best practices for installing rolled roofing over shingles, helping American homeowners make informed decisions for their roofing needs.

What Is Rolled Roofing?

Rolled roofing is a roofing material supplied in rolls approximately 36 inches wide and up to 33 feet long. It is made mainly from asphalt and is surfaced with granules or other coatings to protect against UV rays and weather. There are two common types:

• Mineral-Surfaced Rolled Roofing: Similar granule composition to asphalt shingles, designed to resist weather and UV exposure.
• Polymer-Modified Rolled Roofing (Rubberized): Enhanced flexibility and durability, often self-adhering and waterproof.

This type of roofing is traditionally installed on low-slope roofs or small structures like sheds and garages due to its affordability and ease of installation.

Is It Possible to Install Rolled Roofing Over Existing Shingles?

Yes, it is technically possible to install rolled roofing over existing shingles, but there are several conditions and considerations.

• Roof Condition: The existing shingles must be firmly adhered, undamaged, and free from active leaks.
• Roof Slope: Suitable on low to moderate slopes (generally between 2:12 and 4:12) to ensure proper water runoff.
• Weight and Ventilation: Adding a second layer increases roof weight and can affect ventilation systems.
• Building Codes: Some municipalities restrict the number of roofing layers allowed (commonly not more than two). Check local codes before proceeding.
• Warranty Concerns: Installing rolled roofing over shingles may void existing shingle manufacturer warranties.

Proper preparation of the surface, such as cleaning and patching any loose shingles, is essential for a successful overlay.

Advantages of Installing Rolled Roofing Over Shingles

• Cost Savings: Eliminates the expense of tear-off and disposal of old shingles.
• Quick Installation: Rolled roofing is easier and faster to install than individual shingles or other roofing types.
• Temporary Roofing Solution: Can extend the roof’s lifespan for 5 to 10 years, providing a buffer before a full replacement.
• Reduced Waste: Applying roofing over existing layers minimizes construction debris and landfill waste.

Drawbacks and Potential Risks

• Reduced Roof Lifespan: Rolled roofing generally has a shorter lifespan compared to asphalt shingles (5-10 years vs. 20-30 years).
• Poor Aesthetics: Rolled roofing does not offer the same visual appeal or architectural distinction as shingles.
• Heat Accumulation: Multiple roofing layers can trap heat, potentially stressing the roof deck and increasing cooling costs.
• Pitfalls in Leak Detection: Overlays can mask underlying damage or leaks, making inspections and repairs challenging.

Preparation Steps for Rolling Roofing Over Shingles

Proper surface preparation ensures optimal adhesion and performance of rolled roofing over shingles.

1. Inspect the Existing Roof: Check for loose, curling, or missing shingles, and repair or replace as necessary.
2. Clean the Roof Surface: Remove debris, dirt, moss, and algae that could interfere with adhesion.
3. Repair Leaks or Damage: Patch any leaks or damaged areas with roofing cement or an appropriate sealant.
4. Smooth the Surface: Use roofing cement to nail down any shingles that lift or curl, creating an even surface.
5. Apply Primer or Underlayment: Some manufacturers recommend a primer or roofing felt layer to improve adhesion and moisture protection.

Installation Process for Rolled Roofing Over Shingles

The installation involves careful alignment, adhesive application, and sealing to ensure durability and waterproofing:

1. Start at the Lowest Point: Roll out the roofing material from the bottom edge, working upward to facilitate water runoff.
2. Cut to Fit: Trim rolls as needed to fit roof dimensions and avoid overlaps that could cause bumps.
3. Adhesive Application: Use roofing cement or manufacturer-approved adhesives to bond rolled roofing to shingles firmly.
4. Fastening: Secure the edges with roofing nails or staples, placed at recommended intervals.
5. Seal Seams and Edges: Apply roofing cement over nails and seams to prevent water infiltration.
6. Install Flashing and Drip Edges: Ensure roof edges are protected to direct water away from the roof decking.

Comparing Rolled Roofing to Conventional Shingles

Building Code and Warranty Considerations

Before installing rolled roofing over shingles, it is critical to:

• Check Local Building Codes: Many codes limit roofing layers to two; adding rolled roofing as a second layer is usually acceptable but verify with your local authority.
• Review Manufacturer Warranties: Overlaying may void manufacturer warranties on existing shingles or the new roofing material.
• Hiring Licensed Contractors: Professional installers ensure compliance and proper application.

Maintenance Tips for Rolled Roofing Over Shingles

To maximize the lifespan and performance of rolled roofing installed over shingles, homeowners should:

• Regular Inspections: Conduct twice-yearly checks for cracks, blisters, or edge lifting.
• Immediate Repairs: Address minor damage promptly to avoid leaks.
• Clear Debris: Remove leaves, branches, and dirt that can trap moisture.
• Maintain Gutters and Downspouts: Proper drainage prevents water buildup and damage.

When to Consider Full Roof Replacement Instead

Rolled roofing over shingles is a viable interim solution but not ideal for severely deteriorated roofs. Homeowners should opt for a full roof replacement if:

• The existing shingles are extensively damaged or curling.
• There are repeated leaks or water damage inside the home.
• The roof decking shows signs of rot or structural issues.
• Long-term investment and aesthetics are a priority.

Summary