Roof Coating for Shingles – Causes, Tests & Fixes

Shingle roof coatings are thin layers applied over existing shingles to alter or enhance performance. They come in several formulations, including acrylic, silicone, elastomeric, and bituminous types. Each aims to weatherproof the surface, improve reflectivity, or extend the roof’s life.

Use of coating is typically considered when the underlying shingles are in fair condition and the goal is to seal minor leaks, reduce heat gain, or refresh a tired appearance. When the roof shows widespread damage or advanced wear, re-roofing may be the better long-term choice, so verify guidance from product labels and manufacturer instructions before proceeding.

Types of coatings and how they differ

Roof coatings for shingles come in several types, each with its own properties. Let’s briefly look at the main ones:

Acrylic: These are water-based, affordable, and reflect UV rays to keep your roof cool. They’re great for extending life but may not be as durable as others.

Silicone: Silicone coatings are pricey but offer excellent durability and flexibility. They don’t crack or peel easily and can last up to 10 years. However, they might not reflect UV rays as well as acrylics.

Elastomeric: These are thick, rubber-like coatings that provide superior waterproofing. They’re great for preventing leaks but may not be as reflective or durable as other types.

Bituminous: Made from asphalt and oils, these are cheap and easy to apply. However, they can become brittle over time and lose their flexibility in cold weather.

When coating is NOT recommended

While roof coatings can extend the life of your shingles, there are times when they’re not suitable. Here’s when to skip the coating:

Severe damage: If your roof has significant damage like missing or broken shingles, coating won’t fix that. It’s better to replace those sections.

Curling or buckling shingles: Coatings can’t fix structural issues caused by age or improper installation. If your shingles are curling or buckling, it’s time for a new roof.

Multiple layers: Too many layers of shingles can make your roof too heavy and unstable. Coating won’t solve this problem; you need to remove some layers.

Warranty issues: Some warranties don’t cover roofs that have been coated. Check your warranty before proceeding, or consult a roofer to be sure.

Back to top ↑

Root causes often stem from poor adhesion, moisture, or substrate problems. Improper prep, such as inadequate cleaning or failed primer steps, can lead to premature coating failure. Granule loss and surface contaminants also contribute to uneven performance.

Incompatible coating selections or applying into unsuitable conditions can accelerate wear and staining. Always check label directions, substrate compatibility, and local requirements to identify the most likely failure modes for your roof.

Common environmental and installation factors

Extreme weather conditions can wreak havoc on your roof coating. UV rays, for instance, can break down the coating’s chemicals over time, leading to poor adhesion and accelerated wear.

Ponding water, or water that sits on the roof for extended periods, can also cause damage. It weakens the coating, promoting blistering and peeling.

Temperature swings, especially in areas with harsh winters and hot summers, can cause the shingles to expand and contract. This movement can lead to cracking of the coating and granule loss.

Incorrect application conditions, like applying coatings when it’s too cold or humid, can also result in poor adhesion and failure.

Hidden substrate problems (deck, underlayment, ventilation)

The health of your roof’s underlying structure is crucial for a coating’s longevity. Rotten decking can’t provide the solid base needed for proper adhesion and may cause the coating to bubble or peel.

Wet underlayment, often due to poor attic ventilation, can also undermine your coating. Moisture trapped beneath the shingles can cause delamination, leading to premature failure of the coating.

Inadequate attic ventilation is a common culprit for moisture issues. It traps heat and humidity in the attic, which can then condense on the underside of the roof, wetting the underlayment.

To check for these hidden problems, inspect your attic’s ventilation, look for signs of water damage or rot, and ensure your underlayment is dry before applying any coating.

Back to top ↑

Start with a visual survey of all shingles for curling, cracking, or significant granule loss. Look for visible stains, blisters, or lifted edges that hint at moisture issues. Note any signs of previous repairs and coating patches.

Perform simple on-roof tests such as a gentle adhesion check if safe to do so, and inspect the substrate for dampness or mold. When in doubt, consult product instructions and local building guidance to confirm what tests are appropriate for your site.

Visual checkpoints and what to look for

Use this visual checklist during your inspection to identify potential issues with your shingles and roof coating.

Adhesion and water-penetration tests

These simple on-roof tests help assess your shingles’ adhesion and resistance to water penetration, ensuring a successful coating application.

Tape pull test: Clean a small area of the roof. Apply painter’s tape firmly across the surface, then pull it off quickly. If granules come off with the tape, adhesion may be compromised.

Small patch test: Apply a small amount of coating to an inconspicuous area. Allow it to dry according to manufacturer instructions. Scratch at the edge of the dried coating with a coin or nail. If the coating peels off easily, adhesion may be poor.

Water spray/dry time observation: Lightly mist a small area of the roof with water using a spray bottle. Observe how quickly the water is absorbed and how long it takes for the surface to dry. Excessively slow absorption or drying times may indicate underlying issues with the substrate.

Back to top ↑

Clean the roof surface to remove dirt, debris, and organic growth. Use a suitable cleaner and rinse thoroughly, ensuring the surface dries before coating. Address any algae or moss spots to prevent future staining.

Stabilize loose granules and replace visibly damaged shingles or flashing components. Ensure you have a dry, sound substrate and follow product label instructions for cleaning and pre-coating preparation.

Cleaning methods and products (safe for shingles)

Before you start, understand that aggressive cleaning can damage your shingles. Here’s how to clean safely:

Pressure washing: Keep the pressure low – around 1200 PSI or less. Hold the wand at a 45-degree angle and maintain a consistent distance from the roof.

Soft washing: For algae, moss, or lichen, use a soft wash solution with bleach (3:1 water to bleach ratio) or a specialized cleaner. Apply it gently using a pump sprayer, let it soak for 15-20 minutes, then rinse thoroughly.

Always rinse from top to bottom to avoid streaking and ensure no residue is left behind.

Repair and replacement steps before coating

Inspect your roof thoroughly for damage. Here’s what you need to do:

Replace damaged shingles: If a shingle is cracked, broken, or curling, replace it. Remove the nails with a pry bar, lift out the old shingle, and slide in the new one. Nail it down securely.

Reset loose shingles: If a shingle is just loose, reset its nail tabs by lifting it slightly and hammering the nail back into place. Ensure it’s secure but don’t over-tighten.

Seal nail pops: Nail pops can let water in. Use roofing cement to seal them, then cover with a new shingle tab or flashing.

Check and repair flashing: Ensure all flashings around chimneys, vents, and skylights are watertight. Re-caulk if necessary.

Back to top ↑

Follow manufacturer guidance on temperature and humidity windows and apply with the recommended tools and techniques. Use the specified coverage rate and apply in thin, uniform coats as directed. Allow proper curing time between coats if multiple applications are required.

On-roof adhesion checks and visual cues during cure help verify success. If conditions or results don’t meet the label’s criteria, pause and recheck the product data sheet or manufacturer instructions before continuing.

For peeling or blistering, identify the underlying cause and remove the affected area before reapplying. If staining or discoloration appears, determine whether it’s cosmetic or a sign of bond failure. Replace severely compromised sections as needed.

If adhesion has failed across a large area, stripping may be necessary and reapplication considered, or you might revert to replacing the roof. Always confirm recommended remediation steps via product instructions and warranty terms before proceeding.

Localized repair vs full recoating decisions

First, figure out what’s causing the issue. Refer back to our earlier section on common causes.

If it’s minor – like a few peeling spots due to poor initial application – you might get away with localized repairs. Just clean those areas, prep them, and reapply coating.

But, if the problem is widespread or caused by hidden substrate issues, full recoating or even replacement might be needed. Extensive discoloration, streaking, or blistering are red flags.

Here’s a simple rule: if the bad spots cover more than 30% of your roof, it’s time for a full recoat or replacement. Safety first – don’t DIY if you’re unsure.

Long-term monitoring and maintenance plan

Once you’ve fixed your coating problems, it’s crucial to keep an eye on things. Set a reminder to inspect your roof annually – spring is usually best.

Here’s what to do during each inspection:

– Check for any new peeling, blistering, or discoloration.
– Ensure all vents and valleys are clear of debris.
– Inspect gutters and downspouts for proper water flow.
– Trim back any tree limbs that might scrape against shingles.

Every 3-5 years, give your roof a thorough cleaning. Use a safe cleaner, like one with oxygen bleach or sodium percarbonate. Rinse well afterwards. This helps prevent algae and moss growth, which can damage coating over time.

Back to top ↑

Coatings interact with shingle warranties and building codes, so check compatibility before proceeding. Some manufacturer warranties may restrict coating use or require specific products. Certification or approval notices can influence eligibility.

Read the product data sheet and warranty language carefully, and confirm any local code requirements or endorsements. When in doubt, reach out to the shingle maker or the coating supplier for clarification.

How to verify product compatibility and approvals

Before you start, check the technical data sheet of your chosen roof coating. Look for these:

Adhesion tests: Make sure they’ve tested on similar shingle types to yours.

Primer requirements: Some coatings need a primer. Ensure it’s compatible with your shingles and available.

Temperature limits: Check if the coating can handle your local climate extremes.

What to ask contractors or manufacturers

When hiring a pro, ask these questions to ensure they’re the right fit:

Experience: How many similar jobs have they done?

Insurance: Ask for proof of liability and workers’ comp insurance.

Warranty transferability: Can the warranty be transferred to you if you sell your home?

Expected longevity: How long should the coating last on your specific roof?

Back to top ↑

Consider the upfront material and labor costs along with potential lifespan extension when evaluating coating options. Reflective coatings may reduce cooling loads, depending on climate and roof design. Weigh these factors against the cost of replacement or re-roofing.

Environmental impacts include material sustainability and disposal considerations. Compare coating versus replacement in terms of waste, energy use, and long-term performance by consulting product labels and local guidance.

Estimating costs and expected lifespan gains

The cost of roof coating varies, but expect to pay between $0.50 to $2 per square foot. That’s about half the price of a full replacement.

Lifespan extension? Realistic estimates range from 5 to 15 years. It depends on your climate and the condition of your shingles before coating.

Tip: Get local quotes for accurate pricing. Check with manufacturers or contractors about expected lifespan gains in your area.

Reflective coatings and energy savings

Reflective coatings can lower roof temperatures by up to 30°F. That means less heat transfer into your home, reducing cooling costs.

Expect to save around 7-15% on your cooling expenses. But remember, older shingles might not hold the coating as well, limiting savings.

Note: Energy savings depend on your climate and roof orientation. Expect less savings in cooler regions or with north-facing roofs.

Back to top ↑