White liquid roof coating

Liquid roofing (aka fluid-applied roofing) is an effective method for waterproofing and protecting new and existing roof surfaces with elastomeric roof coating.

Want to know if a liquid roof is right for your business? Click here for a free roof evaluation from an American WeatherStar Approved Contractor.

How Do Liquid Roofs Work?

Liquid roofing systems are applied to roof surfaces in liquid form and cure to create a seamless, UV resistant, and waterproof membrane. Essentially, liquid roofs act as a sacrificial shield protecting roof substrates from the sun, rain, and other environmental conditions.

Liquid-applied membranes are ideal for both flat and pitched roof constructions and are suitable for use on a variety of materials including:

  • Metal
  • Modified bitumen (mod bit)
  • Built-up roofs (BUR)
  • EPDM
  • TPO
  • PVC
  • Concrete
  • Spray polyurethane foam

The coatings that comprise liquid roofing systems have a thicker consistency than your average household paint. They are specifically formulated with greater elongation and tensile strength so they can expand and contract with roofing substrates without becoming damaged or distorted.

Most liquid membrane roofing is applied with a hydraulic airless sprayer or tank spreader. A nap roller or chip brush can be used for smaller applications.

Liquid Roof Coating vs Liquid Roof System

The terms liquid roof coating and liquid roof system are often used interchangeably, but there are some notable distinctions between the two applications.

Liquid Roof Coating

A liquid roof coating by itself can serve as a standalone roofing solution, but for this to be most effective, the roof must be in good-to-excellent condition.

The application of a liquid coating can improve energy efficiency and prolong roof life, but it’s not recommended as a long-term waterproofing solution.

Liquid Roof System

When it comes to waterproofing, a liquid roofing system (or roof restoration system) operates on an entirely different level.

For these systems, roofing substrates are first reinforced with a combination of bonding agents, mastics, sealants, and fabric inlays. This essential “waterproofing” step is what provides liquid membrane systems with superior moisture resistance, durability, and longevity.

Multiple applications of elastomeric coating are then installed over the reinforcement layer fully encapsulating roof surfaces with a seamless, UV resistant, and fully adhered membrane.

Additionally, liquid roof systems are covered by long-term manufacture warranties, whereas liquid roof coatings are not.

The Benefits of Liquid Roofing


The labor and material costs for a liquid roofing system can be up to 70% less than that of a conventional roof replacement or refurbishment.


Liquid-applied coating systems encapsulate roof surfaces to provide a seamless and watertight membrane that stops leaks and resists ponding water.

Extends Roof Life

With proper installation and routine maintenance, a liquid membrane can increase the service life of a commercial roof by up to 20 years, or more.

Additionally, these liquid roof systems can be re-coated numerous times during their lifespan.

Improves Energy Efficiency

Liquid membrane roofing systems produce a bright-white surface that can reflect up to 90% of the sun’s UV radiation. This can significantly reduce the amount of heat transfer from roof surfaces and cut energy costs by up to 30%.

Easy to Install

Liquid-applied coating systems are quick and easy to install. They’re also far less disruptive to building occupants unlike roof tear-off and replacements.

Seamless Protection

Unlike other conventional roofing systems, liquid roofs provide a completely monolithic (seamless) and fully adhered roofing membrane.

Sustainable (Produces Less Waste)

Liquid-applied roof coating systems don’t require the removal of any existing roofing material prior to installation. This greatly reduces the amount of waste contributed to landfills each year.

Types of Liquid Roofing Systems

The following materials form the basis of most liquid membrane roofing systems we see today:


Acrylic coatings are best known for being durable, inexpensive, and easy to work with. They also provide excellent UV protection and mildew resistance.

As a water-based material, acrylics do not hold up well to ponding water and therefore are not recommended for use on low-slope flat roofs where poor drainage may be an issue.

Additionally, acrylic coatings gradually lose dry film thickness as they age, and colder temperatures can be problematic during their installation.

Click here to learn more about acrylic coatings.

Butyl (Butyl Rubber)

Butyl coating is renowned for its exceptionally high elongation and tensile strength. This allows it to accommodate the expansion and contraction (thermal movement) of roof structures.

Butyl coating is mostly used as a vapor retarder in spray foam applications. It’s also quite popular as a roof repair product.

The primary drawback of this material is its low-solids content. This means more liquid material is required during application to reach the desired dry film thickness.

Butyl also tends to discolor over time and can be quite challenging to spray.


Silicone is arguably the most popular type of liquid roof coating on the market today. It’s a solvent-based material with the highest level of UV stability, flexibility, and resistance to ponding water.

Modern silicone coating formulations have a high solids content, meaning less liquid material is needed to achieve a certain dry film thickness (DFT).

Silicone roofing membranes accumulate a lot of dirt and dust (usually within 6 months to a year after installation) which can be a detriment to their reflective qualities. Their surfaces are also extremely slippery when moisture is present.

As a solvent-based material, silicone can be difficult on spray equipment, as well.

Click here to learn more about the pros and cons of silicone coatings.

Polyurethane (Urethane)

Single-component polyurethane is a fast-drying, moisture-cure, liquid roofing material that’s best known for its superior durability, adhesion, and ponding water resistance.

There are two types of polyurethane coating, aliphatic and aromatic.

Aliphatic urethane is white in color and offers better reflectivity. Therefore, it’s typically used as a top coat in liquid membrane roofing systems.

Aromatic urethane has a metallic-gray color and is less UV stable, which is why it’s primarily used as a foundational (base) coating. It’s also less expensive than the aliphatic variety.

Polyurethane coating is a xylene-based material. As such, it produces a strong odor which can be bothersome to building occupants.

Also, urethane coating materials can be difficult on installation equipment.

Click here to learn more about polyurethane coatings.

Spray Polyurethane Foam

Spray polyurethane foam (SPF) is a plural-component roofing material that provides unparalleled thermal resistance (R-value) and waterproofing protection. These systems are incredibly long-lasting, durable, easy to install, and easy to maintain.

Spray foam roofing systems are unique in that they work in conjunction with the elastomeric coating materials mentioned above.

The primary drawback of an SPF roofing system is up-front cost. These systems also have a limited application window and the risk of overspray during installation is a real concern.

Click here for our complete guide to spray foam roofing systems.

Is a Liquid Roof Right for Your Business?

At American WeatherStar, we offer a wide array of liquid roofing solutions for commercial flat and metal roofs. Our roofing systems are proven to stop leaks, extend life, improve performance, and reduce energy costs. Best of all, they cost half as much as conventional roof tear-off and replacements.

Additionally, each of our liquid-applied roofing systems are backed with long-term labor and material warranty options.

If you are considering a liquid membrane system for your commercial roof, click here to schedule a free roof inspection with an American WeatherStar Approved Contractor.