FAQ: Is It Possible to Coat an Old Roof Instead of Replacing It?

Also known as liquid-applied roofing systems, roof coatings are an increasingly popular choice for building owners and roofing contractors alike.

When your roof is reaching the end of its life, you’re likely not excited about the cost of a full roof replacement. If your system is structurally sound but simply getting to be on the older side, you can significantly increase the lifespan of your roof by applying a roof coating. Not only does this mean you don’t have to deal with the lengthy interruption to business operations implied by a roof replacement, but it is also a much more affordable solution.

Not all roofs are great candidates for a roof coating, but it’s worth exploring if you have a roof that is in good shape but getting old. Whether or not you can coat your roof will have to do with the type of roofing system, the condition of the roofing system, and more.

Let’s take a look at everything you need to know about coating an old roof rather than replacing it to help you make an informed decision about your roofing system.

Can You Coat an Old Roof Instead of Replacing It?

If you have an old, structurally sound roof system, you can usually coat it to extend the service life. However, this depends on the type of roofing system you currently have. In order to determine whether your roof is a good candidate for a coating, you will want to have a thorough inspection done.

Professional roofing contractors will look for various criteria in order to determine whether you can confidently coat your roof, including:

• ● The age of the roofing system: How old the roof is and how well it has been maintained will determine whether or not you can apply a coating or whether you need a full replacement
• ● Whether the roofing system is structurally sound: Roofs that aren’t structurally sound will need to be replaced rather than having a coating applied to the existing roof
• ● The existing substrate: Contractors will look at how the existing substrate is adhered, how well it is adhering, etc.
• ● Any existing coating: If there is already a coating on your roof, it doesn’t necessarily mean you can’t re-coat your roof. However, it will determine what type of coating you will need to use. For example, silicone can only be re-coated with a silicone coating.
• ● Coating material adhesion: Performing an adhesion test allows roofers to determine whether the coating will successfully “stick” to your existing roof. This is essential to avoid a roof failure down the road.
• ● The climate: The aging process is highly impacted by the climate, including extreme temperature variation between seasons, lots of rain, salty coastal air, and other considerations.

Once you find out that your roof is in good shape for a coating, the next step is to get the surface prepared for a coating. What preparation entails will depend on your specific roof, but it could include the following:

• ● Reinforcing seams
• ● Removing and replacing substrate saturated with moisture
• ● Making required repairs
• ● Cleaning the surface

Why Might You Want to Coat an Old Roof Instead of Replacing It?

What are the benefits of coating an old roof versus installing a brand-new roof? While one of the most compelling arguments for many building owners is the cost, there are a number of other advantages to this strategy.

The Cost

You are likely already aware that installing a new roof is a significant investment. When you replace your roof, the entire existing roof has to be removed, and a new one is installed. With a roof coating, you will not be removing and replacing any more than 25% of your roof (otherwise, it is likely not a good candidate for a coating in the first place.) This means that installing a roof coating system usually costs building owners half of what they would pay for a complete replacement.

As an additional point, a roof coating isn’t considered a “roofing system” according to building codes but is instead considered maintenance. You typically can not have more than two roofing systems on a commercial structure, meaning you would have to remove at least one of them before replacing your roof if you already have two. You can avoid this expense and hassle by installing a roof coating.

The Warranty

You can usually receive a manufacturer’s 10- to 20-year warranty when applying a roof coating.

This warranty typically includes both materials and labor.

The Protection

Most roof leaks occur at the seams of a roofing system. They can separate from years of temperature fluctuations as well as the adhesive wearing away over time.

When you apply a roof coating, you create a seamless layer over your entire roof. This means that the risk of experiencing a roof leak is significantly reduced.

The Quick Installation

The installation of a roof coating is comparatively very quick compared to a roof replacement. This means that you don’t have to deal with nearly as much interruption to your business operations compared to replacing your roof.

Beyond that, the interruption is reduced because much less equipment is required, and there’s only minimal tear-off.

The Reflectivity and Energy Efficiency

Dark-colored roofs will get much hotter under the heat of the sun, which increases the temperature of your building. If you choose a roof coating that is light in color (such as white or gray), it will bring down the temperature of your roof and your structure. This means that you can pay less for your utility bills and put less wear and tear on your HVAC equipment.

Not a good candidate for a roof coating but interested in benefiting from a more energy-efficient roofing system? You can learn more about the different “cool roofs” types from the U.S. Department of Energy.

What’s the Best Type of Roof Coating?

There isn’t one set answer regarding the best type of roof coating. The right choice for your building will depend on a number of different factors, one of the most important of which is the existing roof type. Other essential considerations are the climate and location.

There are a variety of options when it comes to roof coatings, including silicone, polyurethane, and acrylic. For more information about selecting a roof coating, check out our guide to picking the best roof coating for your commercial roof. You can also learn more about roof coatings in our post comparing silicone and acrylic roof coatings, as well as our article comparing elastomeric roof coatings to other types of roof coatings.

Can You Coat a Shingled Roof?

The Asphalt Roofing Manufacturers Association (ARMA) has the following to say about coating a roof with asphalt shingles:

“Many types of roofing permit the application of a coating for a variety of reasons, such as increasing solar reflectivity, resisting biological growth, improving impact resistance, or increasing roof life. However, ARMA strongly advises against the application of any type of field-applied coating over installed asphalt shingles.”

They go on to say that you will always want to consult with the manufacturer of your shingles before you decide to move forward with a roof coating since there are so many different formulations and types of roof coatings. According to ARMA, local or state building codes might prohibit coating shingles, and the shingle manufacturer might not recommend field coating their products.

There are a number of reasons why it might not be a good idea to put a roof coating on a shingled roof, including that the performance characteristics of shingles might be negatively impacted by field coating, such as:

• ● The impact resistance
• ● The algae resistance
• ● The fire classification

Applying a roof coating to asphalt shingles can result in a number of unfavorable outcomes, including:

• ● The granule surface of the asphalt shingles loosening
• ● Cupping or curling of the shingles
• ● Shrinking of the coating

Beyond that, roof coatings are so successful in creating a non-permeable layer on roofs that it could actually mean that moisture might accumulate within the system.

You also cannot apply roof coatings to tile roofs, whether they are clay, synthetic, or concrete. This is due to the air gaps that occur between the columns and rows of tiles, which create a space where moisture could accumulate underneath the coating.

So, What Kind of Roofing Systems Can You Coat?

You will always want to refer to your manufacturer’s suggestions regarding roof coatings to ensure that your roofing system is a good candidate.

However, there are a number of substrates that are typically well-suited for coatings, including:

• ● TPO: Thermoplastic single-ply roofing material is an increasingly common material used on commercial structures. You will typically need to apply a single-ply primer before coating.
• ● Metal roofs: Metal roofs can be great candidates for coatings, but a special primer will need to be applied beforehand. Additionally, professional roofing contractors will take extra care when applying the coating to any screws, seams, and penetrations.
• ● EPDM: Commonly referred to as “rubber roofs,” you can usually coat this type of roof after applying and washing a rinse-able primer before applying a single-ply primer.
• ● Modified bitumen: An asphalt, plastic/polymerized rubber, and fiberglass material that creates a flexible yet durable membrane, modified bitumen is also a good candidate for roof coatings. It is typically recommended to apply an asphalt bleed-blocking primer first if you are using a silicone coating.
• ● Spray foam roofing: SPF is commonly installed over an existing roof, and applying a coating on top helps to provide necessary UV protection.
• ● Built-up roofing: This type of roofing system has been used in the U.S. for more than one hundred years and is still a common choice for low-slope or flat roofs. Also known as tar and gravel roofs, you can sometimes coat built-up roofs (BUR). You will usually need to apply a spray foam roof first after the gravel has been scraped away and a bleed-blocking primer is applied.

For more information about all of the different types of roofing systems you can use on a flat or low-slope roof, check out our complete guide to flat roofing materials.

How Much Does It Cost to Coat an Old Roof?

A variety of factors will impact the cost of applying a roof coating, including:

• ● Roof size
• ● Type of coating system selected
• ● Amount of preparation required for the substrate
• ● The number of coats
• ● The application rate

Using this information, a roofing contractor can calculate how much of the product will be required to coat your roof. An additional factor is the cost of labor that will be necessary for both preparation and installation.

Building owners won’t just save money with a roof coating versus a full roof replacement, but there can also be tax benefits. You will want to discuss this with your financial advisor if you are curious whether or not this could apply to you, but it’s possible that you could expense the cost of the coating during the installation year rather than simply taking advantage of depreciation over the system’s lifetime.

Do You Want to Extend the Life of Your Existing Roof?

Coating your roof is an excellent way to extend the life of your existing roof rather than incurring the cost of a full replacement. Beyond that, you can usually receive a ten or twenty-year warranty from the manufacturer for both materials and labor, and it can provide added energy efficiency benefits. Perhaps most importantly, a properly installed roof coating can ensure that your building is fully protected from water intrusion.

The first step in the process, if you’re interested in a roof coating system, is to have a reputable professional roofing contractor come out and take a look at your roof. They will be able to let you know whether your roof is a good candidate and, if so, what type of roof coating systems will work with your existing roof.

If you’re thinking about coating a roof in the greater Atlanta area, Colony Roofers is your go-to roofing company. A locally owned and operated business, our entire team is hand selected for their work ethic, integrity, and experience. If you’re looking for a company that specializes in offering the best customer service, high-quality roofing systems, and the most affordable prices, you’ve come to the right place!

Are you wondering whether your roof is a good candidate for a coating? If so, contact us today to schedule a free estimate.