Can You Apply Elastomeric Roof Coating Over Asphalt Shingles?
Elastomeric roof coatings are popular for their waterproofing, durability, and energy efficiency benefits. A common question for homeowners and contractors is whether elastomeric roof coatings can be applied over asphalt shingles. This article explores the feasibility, benefits, and considerations of using elastomeric coatings on shingled roofs, particularly focusing on asphalt shingles, the most widely used roofing material in American homes.
| Aspect | Elastomeric Coating Over Shingles |
|---|---|
| Compatibility | Generally not recommended for standard asphalt shingles |
| Common Uses | Metal roofs, flat roofs, concrete surfaces |
| Benefits | Seamless waterproofing, flexible, UV reflective |
| Concerns Over Shingles | Adhesion issues, limited longevity, trap moisture |
| Preparatory Work | Requires clean, sealed surface; extensive repair recommended |
What Are Elastomeric Roof Coatings?
Elastomeric roof coatings are specialized liquid-applied membranes made from acrylic, silicone, or polyurethane polymers. They form a flexible, elastic barrier over roofing materials that helps protect against water infiltration and UV damage. These coatings can accommodate the natural expansion and contraction of building materials, much like rubber, which is why they are termed “elastomeric.”
Common uses include flat and low-slope commercial roofs, metal roofs, concrete, and built-up roofing systems. The coatings enhance energy efficiency by reflecting sunlight and reducing roof surface temperatures.
Can Elastomeric Coatings Be Applied Directly to Asphalt Shingles?
In general, applying elastomeric roof coating directly over asphalt shingles is not advised. Asphalt shingles have a granulated surface designed to shed water and allow ventilation beneath. Coating over shingles can trap moisture underneath, potentially causing premature shingle deterioration and roof damage.
Additionally, the rough texture and loose granules of old or weathered shingles can prevent proper adhesion of the coating. Without a pristine surface, the elastomeric membrane may peel or crack prematurely.
Why It’s Usually Not Recommended
- Moisture Trapping: Coatings can seal moisture in the shingles, promoting rot and mold.
- Adhesion Issues: The granules on shingles can prevent a secure bond.
- Thermal Movement: Asphalt shingles expand and contract, potentially leading to coating cracks.
- Warranty Concerns: Most shingle manufacturers do not endorse coating applications.
Situations Where Elastomeric Coating Over Shingles May Be Viable
Although not typically recommended, there are circumstances where an elastomeric roof coating might be applied over shingles, such as:
- New, High-Quality Shingles: When shingles are in excellent condition, properly cleaned, and prepared, applying a coating may temporarily extend roof life.
- Underlayments Applied: Installation of a heavy-duty underlayment or reinforced fabric before coating can improve adhesion and waterproofing.
- Specific Products Designed for Shingles: Some manufacturers now produce elastomeric coatings tailored for asphalt shingles with formulas that enhance adhesion and flexibility.
Benefits of Elastomeric Coating on Appropriate Surfaces
When used on compatible roofing materials, elastomeric coatings offer:
- Seamless Waterproof Barrier: Reduces leaks on flat and metal roofs.
- UV Resistance: Protects roofing material from sun damage.
- Energy Savings: Reflects heat and lowers indoor cooling costs.
- Extended Roof Life: Protects against cracking and aging of roof surfaces.
Steps to Prepare a Roof Before Applying Elastomeric Coating
Proper surface preparation is critical for coating success. Steps include:
- Inspect Roof Condition: Check for damage or missing shingles; repairs may be necessary.
- Clean Thoroughly: Remove dirt, moss, algae, and loose granules using a soft brush or pressure washer on low setting.
- Seal and Prime: Use a compatible primer on shingles if recommended by the coating manufacturer.
- Repair Flashing and Roof Penetrations: Ensure all joints, seams, and penetrations are watertight.
- Apply Coating as Directed: Use manufacturer guidelines for temperature and application thickness.
Alternatives to Elastomeric Coating for Asphalt Shingles
For those looking to protect or refresh asphalt shingles without the risks associated with elastomeric coatings, several alternatives exist:
- Shingle Sealers: Specialized sealers designed for asphalt shingles to restore waterproofing and granule adhesion.
- Roof Cleaning and Maintenance: Regular cleaning and moss removal preserve shingle life.
- Cool Roof Coatings for Shingles: Certain mineral-based or silicone coatings specifically formulated for shingled roofs.
- Complete Roof Replacement: If shingles are nearing end-of-life, replacement is often the most cost-effective and safest option.
Common Mistakes to Avoid When Considering Elastomeric Coatings on Shingles
- Skipping Roof Inspection: Failing to assess the shingle condition before application.
- Ignoring Manufacturer Guidelines: Using coatings not designed for asphalt shingles.
- Poor Surface Preparation: Applying over dirty or damaged shingles.
- Applying in Unsuitable Weather: Extreme temperatures or wet conditions can affect adhesion and curing.
Conclusion
Elastomeric roof coatings offer tremendous benefits on many roofing types but are generally not recommended for direct use over asphalt shingles. Issues surrounding adhesion, moisture entrapment, and shingle movement make the application questionable without specialized products or extensive preparation. Homeowners with asphalt shingle roofs should consult with roofing professionals to explore appropriate maintenance and coating options designed specifically for shingled surfaces to ensure long-lasting protection and avoid costly damage.