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What Is The Best Roof Coating?

A roof coating can be the right choice for a property, especially in a time when labour costs and environmental concerns are rising. A coating acts as a barrier to help protect the roof from the elements by increasing UV protection to fight against the sun’s harmful rays and helping to reduce the building’s energy costs. 

It also limits expansion and contraction cycles that lead to premature failure of the underlying membrane in maintenance applications. A coating is also water-resistant, but some materials are better than others when it comes to preventing ponding water. 

A coating can be a good cost-effective option over a full roof replacement. Still, it’s important to do your research concerning the condition of the roof and its location, slope, and exposure to chemicals, heat, and UV rays. 

Types of Roofs

There are many benefits to roof coatings. First, they are the least expensive, most effective way to help make flat roof structures become more energy efficient. Buildings that have roof coatings are much easier to control the temperature inside. 

They also produce less strain on HVAC systems because the coating’s reflective and emissive benefits help reduce energy use. They also prevent chemical damage as well as physical or water damage. Roof coatings can increase your roof’s life by several years, and there is always the option to recoat your roof.

Flat Roofs

Many suggest using silicone for flat roofs such as Gaco S-2000 Roof Coating. One of the primary reasons is because it’s resistant to the standing water that tends to collect on flat roofs. 

Silicone doesn’t absorb water like some of the acrylic-based coatings because it is naturally resistant to water and dampness.

It also doesn’t shed over time or require reinforcing with fabric. This saves time and money on extra labour. A little goes a long way, so you use less of this material than acrylic coatings.

Concrete Green

For concrete roofs, the best choice of the roof coating system is a silicone one such as Acrylic or Urethane based Elastomeric Roof Coatings. 

This solution is seamless and water-based to protect roofs from problems with leaking and rusting. Since it is very reflective, it helps reduce temperatures on rooftops.

Different Types of Roof Coatings on the Market Today

Below are four major types of coatings when considering what the best roof coating is.

Acrylic Roof Coatings

Acrylic is a cost-effective solution that is suitable for a variety of roofs. These are water-based and reflect sun rays, but will lose its mil thickness as it weathers.

Acrylic roof coatings contain different types of acrylic polymer, which are designed to help elongate the coating’s life and improve durability. This roof coating is durable yet cost-effective.

Asphalt emulsions

Another widely used roof restoration material is asphalt emulsion. This product consists of asphalt particles dispersed in water with clay used as a bonding element. 

Generally black or brown in colour, asphalt emulsion contains organic and inorganic compounds, as well as other fillers to add strength and durability.

These coatings are emulsified asphalt and consist of asphalt particles dispersed in water. They utilise clay as the emulsifying component. 

These coatings also contain many types of organic and/or inorganic fibres and fillers to provide extra strength to the coating. 

The coatings are available in black, brown, or as a reflective coating when titanium dioxide or aluminium pigments are added.

These coatings can be applied at approximately 5.6 litres per 100 square feet and can be “swept on” using a push broom. This application method makes for very easy installation, which arguably makes it the best roof coating.

Butyl Rubber

Butyl coatings are best known for their extreme elongation and tensile strength. This solvent-based polymer is highly reflective, fast-drying, and great for roof maintenance and repair. 

Due to their low permeability, butyl rubber coatings are most commonly used as a vapour-retardant barrier over spray polyurethane foam systems in cold storage/freezer applications.

A butyl coating system is suitable for a variety of roof surfaces including metal, modified bitumen, single-ply, built-up roofs, and spray polyurethane foam. They are typically white, grey, or tan in colour and can be sprayed or roll-applied at a rate of about 7.5 litres per 100 square feet.

The primary disadvantages of butyl coatings are their low solid content and their lack of color stability. They require more material to achieve the desired dry film thickness, making them less cost-effective than other elastomeric coatings. 

They can also be challenging to spray and difficult on application equipment.

Polyurethane roof coatings

Polyurethane roof coatings have two main types: aliphatic and aromatic. Aliphatic coatings are costlier but are UV stable, whereas aromatic coatings are less expensive but not as UV stable, which is why it is normally used as a base coating. 

Ideally, an aromatic base coat with an aliphatic topcoat should be employed with urethane roofing. This will ensure durability, the roof will stay cleaner, and unlike an acrylic coating; the urethane roof is more resistant to ponding water.

Polyurethanes are more impact resistant and handle traffic the best of all coatings. There are two main types of polyurethane roof coatings: aromatic and aliphatic. 

Aromatic coatings are less expensive and not UV stable, so they are usually used as a base coating. Aliphatic coatings are more expensive, but are UV stable, hold colour well, and stay cleaner than most other coatings.

Silicone Roof Coatings

Silicone coatings can eliminate the need for a primer. These are moisture-cured, and when exposed to humidity, can even promote their cure. 

Silicone coatings do not get brittle or hard, and weather better than other coatings. This type of coating does, however, hold dirt. It also has resistance to tearing, which means that it should be used with fabric.

Solvent-based silicone coatings

Silicone coatings are typically produced by adding a catalyst and solvents to a silicone base. Because Silicon (Si) is a naturally occurring element, silicone coatings are biodegradable. 

They can be applied to a roofing system using many different techniques, including spraying or rolling. Silicone coatings are available in many colours, including reflective white and translucent.

Solvent-based asphalt coatings

Solvent-based asphalt coatings are often also referred to as cutback coatings because the asphalt (solid at room temperature) is “cut back” with a solvent that liquefies the coating. This allows the coating to be easier applied. Cutback coatings are available in asphalt black or an aluminium-finish reflective coating.

Solvent-based asphalt coatings can be applied with heavy-nap rollers at a rate of around 5.6 litres per 100 square feet. This coating type can often have asbestos in the coating, so users need to be cautious when selecting their raw materials.

Silicone-based coatings can be spray or roller-applied and should utilise a medium-nap roller when rolled. These coatings are applied anywhere from 7 to 13 litres per 100 square feet, depending on the substrate. 

Silicone has two major advantages over the other four types of coatings: 

1) It can resist ponding water for extended periods of time and 

2) It can adhere to most substrates without a primer.

Roof coatings are a great way to keep your roof in shape and to prevent and sometimes repair wear and tear. Acrylic roof coatings, as well as solvent-based silicone coatings, are amongst the best in the business for any roof. It can, however, be a confusing project to tackle. So getting the help of roofing professionals can actually save you money.

The Benefits of Roof Coatings

Elastomeric roof coatings have been around for a long time. That being said, many facility owners and managers are still unaware of the numerous advantages they provide. Before we get into the physical properties found in different types of coating, let’s take a closer look at some of the more significant benefits a coating system provides.

Costs Less

Roof replacements can be quite expensive. Depending on the type of roof you have, a full replacement can cost anywhere from $5 to $15 per sq. ft. A cost-effective roof restoration, on the other hand, provides all the benefits of a new roof but for a fraction of the cost.

Because roof coatings are applied directly over existing surfaces, they require far less labour and material than traditional roof tear-offs and replacements. As a result, you can expect to pay 50-70% less by installing a roof coating system in your building.

Extends Life

Perhaps the best-known quality of an elastomeric coating system is its ability to extend roof life. The average roof only lasts about 20 years, but the addition of a coating system can prolong a roof’s serviceable life by up to 10, 15, or even 20 years.

Elastomeric coatings provide aged roof membranes with a protective, waterproof barrier that stops leaks and improves performance. If properly installed and maintained, a coating system has the potential to be recoated numerous times. It also can significantly reduce the need for constant maintenance and repair.

Reduced construction debris

Recent estimates indicate roofing projects generate 40% of construction waste entering landfills. When workers apply a roof coating at the proper time in a roof’s life cycle, it can delay the need for costly replacement, as well as prevent the need to tear off and dispose of the old insulation and roofing membrane.

Protects Against Roof Leaks

Adding a coating to the roof will give an extra layer to the roof and can protect it from leaks. Not only does the coating add to the roof itself, but it can also help prevent the roof from mould and mildew damage, which can lead to further leaks. 

Keeps Your Building Cooler

A roof with a white or reflective coating will not absorb the sun’s rays; it will reflect them. The reflective property of the coating keeps the building cooler, which can make a big difference in the temperature within; either keeping your building cooler or reducing the cost to keep it cool.

Reduces Energy Costs

Coating your roof is a great way to improve the energy efficiency of your building. Unlike conventional dark-coloured roofing materials, white roof coatings can reflect 80-90% of the sun’s harsh UV rays and diminish the flow of heat to your building. 

This reduces the workloads of HVAC systems during warm summer months and cuts interior cooling costs by up to 20% on average.

Additionally, the superior reflective and emissive qualities of a coating system can significantly cool roof surface temperatures and provide a more comfortable work environment for the occupants of the building. Unconditioned spaces can experience a reduction in ambient temperatures as well.

Improves Sustainability

In recent years, the demand for more sustainable roofing solutions has grown considerably due to more stringent environmental regulations and building codes, as well as increased concern for the environment.

Roof tear-offs contribute to the vast pile-up of waste in landfills each year. In contrast, there is no tear-off required prior to the application of a roof coating system, allowing you to reuse existing roofing materials with minimal impact on the environment. As mentioned above, the prospect of recoating also contributes to increased sustainability.

Environmentally Friendly

In addition to improved sustainability efforts, many of today’s elastomeric coatings are developed with little to no VOCs (volatile organic compounds), making them much safer for the environment. 

Improves Green Reputation

Depending on your particular company’s goals, you can show customers, vendors, and associates that you are doing everything possible to make the building “green”. 

This can be great for your reputation. Green roofing, via a roof coating, relatively speaking, is an affordable and straightforward way to accomplish this.

Aesthetic improvements

Rather than replacing an unsightly, aging roof for aesthetic purposes, managers can improve the appearance of a roof that is visible from the ground or adjacent buildings through the application of a coating.

For example, aging, prefinished, metal roof systems might need to be replaced, due to fading or peeling finishes, because traditional coating systems do not have a good track record of success when applied to the existing finishes. Newer-generation coatings contain Kynar pigments and can effectively restore roofs to an aesthetically pleasing condition.

Physical Properties to Consider

Every roof is different. That’s why it’s important to evaluate certain physical properties of a coating to ensure its suitability in a particular roofing environment. Each property listed below, as well as other technical data, can be found in the manufacturer’s product datasheets.

Elongation

Elongation is the percentage in which a material can be stretched before it breaks. Most elastomeric coatings typically measure anywhere between 250-900%. The higher the elongation value, the more suited a coating is to endure the normal expansion and contraction of a roof structure without cracking, thinning, or peeling off.

Tensile Strength

Tensile strength is the amount of pressure a material can withstand before it breaks. Depending on chemistry type, most elastomeric coatings rate anywhere from 250-1200 psi (pounds per square inch).

Elongation and tensile strength are closely related but in an inverse way. As one increases, the other decreases. The best roof coating formulas balance the two properties to provide a strong, durable membrane that can adequately stretch and move with roof surfaces.

Permeability (Moisture Resistance)

Permeability, or perm rating, is the state or quality of a material or membrane that causes it to allow liquids or gases to pass through it. This value varies greatly depending on the type of coating.

For example, acrylics have a high perm rating, meaning they are very breathable. Silicones, on the other hand, have a lower perm rating meaning they have superior resistance to moisture transmission. It’s important to note that higher permeability does not equate to inferior weather resistance.

Reflectivity

Reflectivity measures the amount in which a material can reflect light. It is typically represented as a percentage between 0-100%, with at least 85% being considered good reflectivity. 

Unlike conventional, dark-coloured roofing materials, white roof coating systems reflect 80-90% of the sun’s energy back into the atmosphere, significantly reducing the risk of heat gain throughout the roof structure.

Emissivity

Emissivity refers to a material’s ability to release absorbed heat. This property is usually represented as a decimal between 0 and 1, with 0.65 being considered ideal for an elastomeric roof coating. 

This means 65% of the sun’s thermal energy is emitted away from the roof, thus reducing building heat loads and lowering cooling costs.

Solids by Volume

Solids by volume are the measure of how much solid material will remain after a substance has dried. 

Understanding this property is critical in order to properly achieve the required dry film thickness specified for certain coating systems. 

While it has no bearing on the performance of a coating, this particular property is certainly worth some consideration.

Though the physical properties highlighted above are the most notable in terms of performance, there are other data points to consider as well. 

Any of the coatings covered can be used on the surface of your flat roof, it’s just that some work better than others. 

The key is to contact a roofing professional who can give you the best advice on which coating to pick for your roof. Roof coatings can be very beneficial and are worth the investment in most cases.

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