Homeowners often wonder if it is possible and practical to install roll roofing over existing asphalt shingles. This question arises mainly when considering cost-effective roof repairs or quick fixes. Understanding the feasibility, benefits, and risks of layering roll roofing on top of shingles can save money while maintaining roof integrity. This article explores the technical aspects, building code considerations, and installation best practices for using roll roofing over shingles.
| Aspect | Key Points |
|---|---|
| Feasibility | Possible but not always recommended |
| Building Code | Restrictions on multiple layers in many areas |
| Installation | Surface prep and ventilation critical for success |
| Longevity | May reduce overall roof lifespan |
| Cost | Cheaper upfront but potential higher long-term costs |
What Is Roll Roofing and How Does It Compare to Shingles?
Roll roofing is a type of roofing material made from asphalt-saturated organic or fiberglass mats, typically sold in rolls measuring about 3 feet wide. It is often used on low-slope roofs and provides a quick, affordable roofing solution. Asphalt shingles, on the other hand, are individual overlapping elements designed for pitched roofs and generally last longer and offer better aesthetic appeal.
Is It Technically Possible to Install Roll Roofing Over Existing Shingles?
Yes, it is technically feasible to apply roll roofing over asphalt shingles. The existing shingles provide a base, potentially reducing labor as the old roof does not need removal. However, this practice is generally only advisable for roofs in good condition without significant damage or moisture issues. The success depends on proper surface preparation and ensuring no underlying roofing defects.
Building Codes and Regulations Around Layering Roofing Materials
Many local building codes limit the number of roofing layers allowed. In most U.S. jurisdictions, a maximum of two layers is permitted. If two layers already exist, additional roofing often requires full removal.
Before applying roll roofing over shingles, homeowners must verify local roofing regulations to ensure compliance and avoid issues during future inspections or when selling the property.
Advantages of Installing Roll Roofing Over Shingles
- Cost Savings: Eliminates the cost of tear-off and disposal of old shingles.
- Time Efficiency: Faster installation process.
- Temporary Protection: Useful for short-term roof warranty extensions or quick fixes.
Potential Risks and Disadvantages
- Trapped Moisture: Layering can trap water, causing rot and mold growth.
- Reduced Lifespan: Additional layers add weight and may decrease overall roof durability.
- Warranty Voidance: Manufacturer warranties might not cover roofs with multiple layers.
How to Properly Prepare and Install Roll Roofing Over Shingles
For optimal results when installing roll roofing over shingles, follow these steps:
- Inspect Roof: Check the shingle layer for damage, leaks, and decay.
- Clean Surface: Remove dirt, debris, and loose granules from shingles.
- Repair Imperfections: Fix any cracks or damaged shingles before installation.
- Apply Roofing Primer: Use a primer compatible with shingles and roll roofing to enhance adhesion.
- Install Underelement: Consider placing a synthetic underlayment for added moisture barrier protection.
- Roll Roofing Installation: Follow manufacturer guidelines for overlapping, nailing, and sealing edges.
When Is It Better to Remove Old Shingles Before Installing Roll Roofing?
Removing old shingles is recommended when:
- There are existing multiple roofing layers.
- The current shingles are damaged, curling, or missing granules.
- Roof ventilation is inadequate.
- The roof structure shows signs of rot or water damage.
Performing a full tear-off ensures a clean, smooth surface to properly install roll roofing, improving roof performance and lifespan.
Cost Comparison: Overlay vs. Tear-off and Replacement
| Option | Estimated Cost per Square (100 sq ft) | Pros | Cons |
|---|---|---|---|
| Roll Roofing Over Shingles | $75 – $120 | Lower upfront cost, faster | Shorter lifespan, possible code issues |
| Removing Shingles + New Roll Roofing | $150 – $250 | Better durability, code compliant | Higher cost, longer duration |
Common Questions About Applying Roll Roofing Over Shingles
Will Roll Roofing Stick Well to Asphalt Shingles?
When properly prepared and primed, roll roofing adheres effectively to asphalt shingles. On older or dirty shingles, adhesion can fail, increasing risk of leaks.
Does Roll Roofing Over Shingles Affect Roof Warranty?
Most roofing product warranties do not cover failures related to multiple roofing layers. Always check warranty terms before overlay installation.
Can Roll Roofing Prevent Leaks When Laid Over Shingles?
Roll roofing creates a waterproof layer; however, if the underlying shingles have damage, leaks can still occur through penetrations or edges.
Tips for Maintaining Roofs with Roll Roofing Over Shingles
- Regularly inspect for signs of moisture or deterioration.
- Ensure gutters and downspouts direct water away properly.
- Address any roof damage immediately to avoid layered roof complications.