We may earn revenue from the reviewed options, we ordered seven top sealants and put them to the test. Since we had a roofing project coming up, it was the perfect opportunity to take some of these products for a spin.
First, we wanted to test how difficult each product was to apply. We followed the manufacturer’s instructions (most recommend three coats), applying the sealants to our roof as well as a sheet of sheathing for side-by-side comparisons. To test the tapes and caulk, we covered some gaps we created between scrap boards and left them out in the rain and snow.
At the end of the 2-week test period, we scored each product and gave it an award based on performance. Overall, these products do exactly as they claim: create effective barriers against moisture and seal gaps.
What to Consider When Choosing a Roof Sealant
With so many roof sealants on the market, choosing the best one for your specific needs can be difficult. To narrow down the choices, it helps to review and compare the characteristics of roof sealants. The following considerations can help take the guesswork out of determining the best roof sealant for you.
Purpose
Roof sealants serve two main purposes: protecting roofs by creating a barrier against moisture and sun, and repairing minor leaks before they cause serious damage. Although some roof sealants will be effective on virtually any type of roof, most are formulated to work with specific roofing materials.
Roofing materials like asphalt shingles, composite shingles, metal, and rubber have different characteristics that require special attention when choosing a sealant. Additionally, whether a roof is flat or slanted can impact which sealant is ideal. Finally, whether the goal is to repair minor damage or seal an entire roof also needs consideration when choosing the best type of roof sealant.
Roof sealants can be divided into two categories: solvent-based and water-based. While solvent-based sealants are highly resilient against the elements, they are generally more expensive, thicker, and harder to apply. Water-based sealants are more affordable and emit fewer odors, but they aren’t as weather-resistant. They may degrade several years earlier than solvent-based sealants and, therefore, may require more frequent maintenance.
Solvent-based sealants also require the use of a respirator during application to avoid inhaling the solvent fumes, whereas no mask is needed for water-based sealants. Disposing of solvent-based sealants can also be trickier since they may be considered household hazardous waste and must be disposed of at an appropriate facility. Water-based sealants can be discarded in a household trash bin after the container’s contents have fully dried.
Within the two main categories, there are five types of roof sealants: acrylic, polyurethane, silicone, rubber, and sealant tape.
- Acrylic: The most common variety, acrylic roof sealants are specifically made to deflect UV rays. They are popular in western and southwestern states where sun damage to roofs may be the primary concern. Acrylic sealants are also moderately moisture-resistant but don’t provide a waterproof barrier or hold up well against standing pools of water, which is a common issue on flat roofs.
- Polyurethane: Polyurethane sealants are resilient against moisture but not very resilient against UV rays. This makes polyurethane sealants preferable in areas with more rain and snow than sun.
- Silicone: Silicone sealants offer excellent protection against moisture and UV rays, making them suitable for any weather, including heavy rain and sun. The main downside of silicone sealants is that they’re often expensive, which can make coating a whole roof financially prohibitive.
- Rubber:Rubber sealants consist of liquid rubber that acts as a powerful guard against the sun and rain. These sealants are often available in thin, water-based formulas that are easy to apply. Their watery consistency makes them great for sealing small cracks and leaks.
- Sealant tape: Sealant tape is a thin strip of moisture-resistant material for repairing minor leaks and sealing vulnerable roof seams. The tape has an adhesive backing that applies directly to the roofing material, making it easy to use without a messy or labor-intensive application process. Sealant tape is generally more affordable than other types of sealants, but it’s not designed to cover large sections of a roof.
Waterproofing
Every type of roof sealant offers some protection against water, but not all are capable of producing a completely waterproof membrane. If the main goal is waterproofing the roof, the best sealant types are rubber, silicone, and polyurethane. Each tolerates heavy rain and pooling water that acrylic sealants and sealant tapes can’t handle.
Regardless of the type of sealant used, multiple coats are often required to create a completely waterproof seal over the entire roof. If that’s the intended purpose, it’s especially important to follow the manufacturer’s directions for application. Repairing isolated leaks may be an exception, however, as a single coat of most sealants is sufficient for waterproofing small areas.
Reflectivity
A roof’s solar reflectivity is the amount of sunlight it’s capable of reflecting, which translates into less heat absorption, which equates to an overall cooler home, reduced air conditioning use, and a lower electricity bill. Depending on the sealant’s material and color, adding a layer of roof sealant can dramatically enhance a roof’s solar reflectivity. Some manufacturers claim their products can deflect up to 92percent of UV rays.
Rubber, acrylic, silicone, and polyurethane sealants all possess high levels of reflectivity. Along with the sealant’s material composition, the color of the sealant will play a major role in its level of reflectivity. White and light-colored sealants generally possess the highest reflectivity, while black and darker-colored sealants offer the lowest reflectivity.
Longevity
A roof sealant’s longevity will vary among manufacturers and the sealant’s material, but most will last between 10 and 20 years. Sealant tapes will usually last this long without any special application process, but the longevity of liquid sealants depends on the thickness of the applied coating. A coating of liquid sealant 30 mils (a mil is equal to 1/1000 inch) thick can last 10 years longer than a sealant 20 mils thick. Obtaining the proper thickness might require several coats of sealant, and sealant manufacturers will often specify the required coats to obtain the desired thickness.
Another factor that impacts a roof sealant’s longevity is proper application; a roof sealant applied during cold weather, to a wet or dirty roof, or before rain without adequate time to cure, won’t last as long as a correctly applied sealant. Maintaining the performance includes inspecting the roof at least once a year under normal weather conditions and repairing any damage after adverse weather, like heavy rain, snow, and intense sun exposure. Some sealant manufacturers and roofing contractors recommend resealing a roof every 5 years, regardless of its condition, to maximize longevity.
Ease of Application
Thicker, solvent-based sealants, like silicone and some rubber sealants, are harder to apply than water-based sealants, like acrylic and water-based rubber sealants. However, thinner sealants will likely require multiple coats to achieve the necessary thickness, especially when aiming for a waterproof seal on the entire roof. Also, thicker sealants may be easier to work with in hot weather since thin sealants can become too runny to achieve a thick coat.
Both thick and thin sealants can be applied with a paint brush or a roller, but with thinner sealants, there is the additional option of using a paint sprayer. For isolated repair work, sealants in caulking tubes can more easily access nooks and crannies that would be difficult to reach with a brush, and sealant tapes can be easily applied to the affected area with minimal effort and no additional tools.
Q. How do you use roof sealant?
Depending on the sealant’s thickness, you can apply it with a paint brush, paint roller, paint sprayer, or hand trowel. Some roof sealants come in tubes that are applied with caulk guns.
Q. How long does a roof sealant take to dry?
The drying time for a roof sealant will depend on the sealant’s composition and the weather at the time of application. Most sealants take between 8 and 24 hours to fully dry.
Q. How do you remove roof sealant?
You can usually use a plastic putty knife to remove roof sealant. Just be careful not to damage the underlying roofing material.
Meet the Tester
Tom Scalisi is a full-time DIY and construction writer for many of the largest websites in the industry, including BobVila.com, This Old House, Family Handyman, and Forbes as well as his own pest control blog.
Additional research provided by James Fitzgerald.
