Can You Apply Elastomeric Roof Coating Over Asphalt Shingles?
Elastomeric roof coatings offer a flexible and protective layer that can enhance roofing longevity. However, many homeowners and contractors ask, can you put elastomeric roof coating over shingles? While elastomeric coatings are excellent for certain roof types, their compatibility with asphalt shingles requires careful consideration. This article explores the feasibility, benefits, and limitations of applying elastomeric roof coatings over shingled roofs, along with proper preparation and application techniques to ensure lasting results.
What Is Elastomeric Roof Coating?
Elastomeric roof coatings are liquid-applied products designed to provide a seamless, highly flexible protective membrane over roofing substrates. Comprised primarily of acrylic polymers, these coatings offer waterproofing, UV resistance, and reflectivity that help extend roof life and reduce energy costs.
Key characteristics of elastomeric roof coatings include:
- Elasticity: Expands and contracts with temperature variations without cracking.
- Waterproofing: Creates a watertight seal to prevent leaks.
- UV Protection: Shields roofing materials from sun damage and degradation.
- Energy Efficiency: Reflects solar heat, lowering cooling expenses.
Common Roof Types Suitable for Elastomeric Coatings
While elastomeric coatings are highly versatile, they are best suited for the following roof types:
- Flat or low-slope roofs: Concrete, modified bitumen, built-up roofs (BUR), and metal.
- Concrete and masonry surfaces such as parapet walls and roof decks.
These substrates provide a suitable base for the adhesive and protective qualities of elastomeric coatings.
Can Elastomeric Roof Coating Be Applied Over Asphalt Shingles?
Technically, elastomeric roof coatings can be applied over asphalt shingles, but this practice is not universally recommended. The suitability depends on several factors:
- Condition of Existing Shingles: Coatings perform best on tightly bonded, intact shingles without damage or curling.
- Roof Slope: Since shingles shed water through overlapping layers, coatings must maintain flexibility and adhesion on sloped surfaces.
- Manufacturer Approval: Some coating products explicitly state compatibility with shingle roofs, while others do not.
In many cases, the performance of elastomeric coatings on shingled roofs may be limited in durability and effectiveness compared to application on flat roofs or non-shingle materials.
Benefits of Applying Elastomeric Roof Coating Over Shingles
When done correctly, elastomeric coatings offer several advantages for shingled roofs:
- Extended Roof Lifespan: Enhanced weather sealing can slow down shingle deterioration.
- Reflection of UV Rays: Coatings reflect sunlight, reducing heat absorption and potentially lowering indoor temperatures.
- Water Resistance: Helps fill small cracks and gaps between shingles, mitigating minor leaks.
- Cost-Effective Maintenance: Applying a coating may delay the need for a full roof replacement.
Challenges and Limitations to Consider
Despite potential benefits, there are inherent challenges:
- Adhesion Problems: Granulated shingle surfaces can affect coating adherence, leading to peeling or blistering.
- Moisture Trapping: Coatings may seal moisture within shingles, accelerating deterioration or mold growth if proper drying isn’t ensured.
- Limited Manufacturer Warranties: Many elastomeric coatings don’t warranty their use over asphalt shingles.
- Appearance Impact: Coatings can alter the visual texture and color of shingles, sometimes negatively affecting curb appeal.
Proper Preparation Before Coating Asphalt Shingles
To improve outcomes, thorough preparation is essential:
- Roof Inspection: Check for damaged, loose, or curling shingles and make repairs or replacements.
- Cleaning: Remove debris, moss, algae, and dirt using appropriate cleaning agents.
- Drying: Ensure shingles are completely dry to avoid moisture entrapment.
- Priming: Some materials require applying a bonding primer designed for shingle surfaces.
Application Process for Elastomeric Coating on Shingles
Correct application techniques include:
- Multiple Thin Layers: Apply several thin coats rather than one thick coat for enhanced flexibility and adhesion.
- Use of Quality Brushes or Rollers: Ensure even coverage and avoid pooling in valleys or gaps between shingles.
- Follow Manufacturer Instructions: Always adhere to recommended drying times and temperature conditions.
Alternatives to Elastomeric Coating on Shingle Roofs
For homeowners considering roof maintenance, other options might better suit shingle roofs:
- Roof Sealants: Seal and fill smaller cracks in shingles without full coating.
- Roof Replacement: When shingles are extensively damaged, replacement may be more cost-efficient long term.
- Cool Roof Shingles: These are specially designed asphalt shingles with reflective coatings integrated at manufacture.
- Professional Roof Inspection and Maintenance: Regular inspections can address issues early and extend roof life without coating.
Summary Table: Applying Elastomeric Coating Over Asphalt Shingles
| Aspect | Considerations | Recommendations |
|---|---|---|
| Surface Condition | Intact, well-adhered shingles required | Replace damaged shingles before coating |
| Adhesion | May be challenging on granulated surfaces | Use primer if recommended; thin coats |
| Water Resistance | Coating improves moderate leak resistance | Address major leaks before coating application |
| Durability | Limited warranty and variable lifespan | Consider professional evaluation to weigh costs |
| Aesthetics | May change shingle appearance | Test on a small area first if appearance matters |
| Energy Efficiency | Reflective coatings can reduce heat load | Choose light-colored elastomeric coatings for best effect |