If you have a low slope or flat roof, you may be considered applying a roof coating. Roof coatings are an excellent way to extend the life of a roof and improve energy efficiency. Yet, you need to apply the roof coating when the forecast is sunny or overcast, as they require a certain amount of time to cure. If a roof coating hasn’t fully dried before it’s exposed to moisture, there may be problems. So, how long does a roof coating need to dry before rain? Understanding drying times and best application practices can help you avoid a costly mistake.
Key Takeaways
- Roof coatings protect and extend the life of a roof by sealing it against UV damage, water infiltration, and general wear. They must be applied under proper weather conditions for the best results.
- Drying time varies by coating type: Acrylic coatings take 24-48 hours to fully cure, silicone needs about 24 hours, polyurethane requires 8-24 hours, and asphalt-based coatings may need up to 24 hours before they resist rain.
- Roof coatings are not immediately waterproof. While silicone coatings are naturally moisture-resistant, acrylic and polyurethane coatings require full curing before they can withstand rain exposure.
- If a coating gets wet before curing, it can result in washing away, streaking, poor adhesion, or extended drying time, leading to reduced effectiveness and the need for reapplication.
What are Roof Coatings?
Roof coatings are liquid-applied protective layers designed to seal and protect a roof from UV damage, water infiltration, and general wear and tear. These coatings can be used on various roofing materials, including metal, asphalt, modified bitumen, and single-ply membranes.
Common types of roof coatings include:
- Acrylic Roof Coatings: Water-based and highly reflective, these coatings are great for energy efficiency but require dry conditions for proper curing.
- Silicone Roof Coatings: Ideal for wet climates due to their water resistance, but they attract dirt over time.
- Polyurethane Roof Coatings: Highly durable and impact-resistant, often used for commercial roofs with heavy foot traffic.
- Asphalt-Based Roof Coatings: Typically used on built-up roofs, providing strong waterproofing and UV protection.
Best Practices for Roof Coating Application
For optimal results, always check the weather forecast before applying a roof coating. Ideally, you should schedule the application when you can expect at least 24 to 48 hours of dry weather to allow for proper curing. Additionally:
- Apply coatings in temperatures between 50°F and 85°F for the best adhesion.
- Avoid high humidity, as excessive moisture in the air can slow the drying process.
- Follow manufacturer guidelines for re-coating or touch-ups if rain does occur unexpectedly.
A flat roof with visible water droplets and reflections after rainfall.
How Long Does a Roof Coating Need to Dry Before Rain?
Drying time differs, depending on the kind of roof coating applied. That said, for any coating, drying time is important. If a roof coating doesn’t fully dry before exposure to moisture, such as humidity or rain, issues may arise. To avoid adhesion, streaking, or failure, it’s crucial to follow manufacturer recommendations and apply coatings when there is ample time for it to dry completely.
How long does a roof coating need to dry before rain? Here is a breakdown of drying times:
Acrylic Roof Coatings
Acrylic roof coatings are water-based. Within 4-8 hours, they are dry to the touch but take around 24-48 hours to completely cure. Because of the water base, any moisture within the first 24 hours will wash away parts of the coating—if not everything. As such, acrylic roof coatings should be applied only when there is at least two days of no rain in the forecast.
Silicone Roof Coatings
Known for being moisture-resistant, silicone coatings need around 2-6 hours to dry to the touch and 24 hours to cure. Unlike acrylic coatings, silicone is naturally waterproof once it sets, so light rain may not cause significant issues. However, heavy rain before full curing can still weaken adhesion.
Polyurethane Roof Coatings
Solvent-based polyurethane roof coatings are not as waterproof as silicone. They take around 8-24 hours to dry. After 24 hours, these roof coatings are usually cured, but they need at least a full day without rain to ensure proper bonding and durability.
Asphalt-Based Roof Coatings
Typically drying within 6 to 12 hours, asphalt-based coatings vary depending on their formulation. Some may need up to 24 hours before they can fully resist rain. These coatings often contain oils that need time to evaporate, so moisture exposure too soon can lead to softening or improper curing.
Are Roof Coatings Waterproof?
The answer depends. While most roof coatings are designed to increase a roof’s water resistance, they are not immediately waterproof upon application. The degree of waterproofing depends on the coating type and whether it has fully cured.
For example, silicone roof coatings offer the highest level of waterproofing. Once cured, they create a seamless, watertight barrier that repels moisture effectively. Meanwhile, acrylic roof coatings need to fully cure before they can withstand any moisture. If exposed to moisture too son, they will degrade or wash away, leaving open holes that water can breach.
What Happens If a Roof Coating Gets Wet Before It Cures?
Water droplets form on a flat roof after rain, demonstrating the effectiveness of a recently applied waterproof roof coating.
If a roof coating is exposed to rain or moisture before it has fully cured, several problems can arise:
- Washing Away: Water-based coatings, such as acrylics, are especially vulnerable to being washed away by heavy rain. If this happens, the coating will need to be reapplied.
- Streaking and Discoloration: Rain can cause uneven drying, leading to streaks, blotches, or an inconsistent finish. This not only affects the appearance but may also reduce the coating’s effectiveness.
- Poor Adhesion: Moisture trapped under the coating can prevent it from bonding properly to the roof surface, leading to peeling, bubbling, or flaking over time.
- Extended Drying Time: High humidity and unexpected rain can slow down the curing process, delaying when the roof is fully protected.
If rain is in the forecast within 24 to 48 hours, it’s best to reschedule the application to ensure the coating has ample time to dry. If a sudden storm occurs after application, check for damage once the roof is dry and reapply the coating as needed.
Reasons to Use a Professional Roof Coating Service
Apply a roof coating may seem like a simple task, but improper application may lead to costly repairs. Here are some reasons why you should hire a professional roofing contractor:
- Correct Application: A professional team will be diligent about the application, ensuring even coverage and proper thickness.
- Weather Monitoring: Professionals will schedule the coating at the most opportune time to avoid any weather-related issues. In the event rain does end up on the radar, the team will do whatever necessary to make sure the coating doesn’t fail.
- High-Quality Materials: Contractors use top-grade products suited to your roof’s specific needs.
- Long-Term Performance: Properly applied coatings last longer, reducing the need for frequent reapplications.
FAQs About Roof Coatings and Rain
1. Can I apply a roof coating if rain is expected within 24 hours?
No, it’s not recommended. Most roof coatings need 24-48 hours of dry weather to fully cure. Applying a coating when rain is expected increases the risk of poor adhesion and wash-off, particularly with acrylic coatings.
2. How can I tell if my roof coating is fully cured?
A roof coating is fully cured when it is no longer tacky to the touch and has achieved its intended hardness. This process can take anywhere from 24 to 48 hours, depending on the coating type, temperature, and humidity levels.
3. What should I do if unexpected rain falls on my freshly applied roof coating?
If rain occurs before the coating cures, inspect the surface for streaking, peeling, or areas where the coating has washed away. In most cases, reapplication or touch-ups may be necessary once the roof is dry.
Five workers in safety vests and hard hats apply a white reflective coating to a flat commercial roof, with some areas still showing the underlying black layer.
Get Your Liquid-Applied Roof Coatings from a Trusted Roofing Contractor
How long does a roof coating need to dry before rain? At least 24 hours, in most cases. Roof coatings are a great way to extend the life of your roof and get better protection from the elements. However, coatings need to be applied when the temperature and weather is right. To ensure your roof coating is applied correctly and dries before rain, trust the professionals at RGB Construction. Our experienced team knows how to work with various roof coatings to provide long-lasting protection for your home or business.
Call us today at 856-264-9093 or fill out our online form to schedule a consultation. Protect your roof with expert roof coating services from RGB Construction!
