Different Methods for Waterproofing a Flat Roof

Best Flat Roof Waterproofing Methods

There are several flat roof waterproofing methods. Which is the best depends on factors such as the environment, size of the roof, and cost. Each has benefits that are important to know as you decide the appropriate method for your roof. Allied Roofing Solutions details each method with benefits in this article.

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Your roof is one of the most important parts of your house or commercial building because it keeps your property safe from the outside elements. Most of the time, people don’t even look at your roof except when it is in disrepair or worn. Your roof functioning as it should depends on keeping up with the maintenance. It is essential that you maintain and regularly service a flat roof to keep it attractive and functioning properly.

Maintaining a flat roof requires waterproofing since this type of roof has challenges with draining water. When you repair or replace a flat roof, the material used must be waterproof. There are several waterproofing applications available from which you can choose. At Allied Roofing Solutions, we have experience with all types of roofs, including flat ones. We can recommend the materials you need for your specific roof based on several factors such as the environment, the type of structure, and the cost. In this article, you will learn about the different types of waterproofing methods and the specifics of each. This information can help when you’re going to repair or replace your flat roof.

Different Methods for Waterproofing a Flat Roof

Generally, when you spot damage on a flat roof, you will have a choice of three main types of waterproofing for flat roofs–liquid waterproofing, reinforced bitumen membrane, and single-ply membrane. Several factors determine what waterproofing method you use, including:

  • Roof size
  • Budget
  • Type of structure
  • Local environment

Liquid Waterproofing

Liquid waterproofing involves applying a coating to the roof. The three most popular types of elastomeric coatings are acrylic, silicone, and urethane. Elastomer coatings are elastic substances that resemble rubber, which are applied as a fluid but have elastic-type properties. The coating becomes a membrane that expands and contracts with the base to which it is applied. Waterproofing coatings are available with liquid fleece membranes, fiberglass liquid, or glass-reinforced plastic. The lifespan is anywhere from 10 to 20 years, depending on the installation process, the maintenance after its installation, and the quality of the product used.


Acrylic is a water-based elastomeric coating that is applied to roofs with some slope. This type of waterproof coating can be used on all roof types such as slate roofing or aluminum roofing but is commonly used on flat roofs. Acrylics are typically 52% solids by volume and 48% water, meaning that upon application almost half of the product is lost through evaporation.

Silicone is a resin-based coating that is 96% solids and 4% carrier, meaning 96% of what goes down stays on the roof. Silicones are twice as resistant to weathering as acrylics but are also more expensive.

Urethane has the most impact resistance of any elastomeric roof coating. However, urethanes are expensive compared to acrylic and silicone and don’t hold up well to standing water.

Thermoplastic Polyolefin Waterproofing Method

Thermoplastic Polyolefin (TPO) Membrane

Thermoplastic polyolefin (TPO) is a single-ply white membrane used for waterproofing flat roofs. Because it is a white membrane, it reflects heat instead of absorbing heat. The membrane will naturally expand and contract with temperature changes. It comes in large rolls and is adhered or mechanically attached to the substrate with heat, typically a hot-air gun, to weld the seams and make them waterproof. This membrane is a great option for a flat roof, a low-slope dormer, or a building that discharges oil and fat through the ventilation system (e.g., a restaurant). A TPO membrane has a lifespan of up to 40 years.

Benefits of TPO Roofing:

Energy efficiency

It is UV resistant and can withstand higher temperatures, making it more cost-effective to cool your home or commercial building in the hot summer.

It is less prone to grow mold and accumulate dirt, and more resistant to the impact of falling debris.

TPO comes in large rolls that are laid out on the roof deck and then hot-air welded at the seams.

It comes in several color options that camouflage dirt as it builds up over the years.

Polyvinyl Chloride (PVC) Roofing Membrane

Polyvinyl Chloride (PVC) Roofing Membrane

PVC roofing membrane is similar to TPO in that it is a single-ply white membrane and has some of the same characteristics. The main difference is that PVC roofing is more flexible and has existed for a longer time than TPO. It only comes in white, meaning it will show the dirt over time. A PVC roofing membrane will last around 25 years when it is installed properly.

EPDM Roofing Membrane

EPDM (ethylene propylene diene terpolymer) roof coating is an extremely durable synthetic rubber roofing membrane. The two primary ingredients are ethylene and propylene, which are derived from oil and natural gas. It is available in both black and white. Because it is made from rubber, the membrane has several benefits that make it increasingly popular with both residential and commercial flat roofs.

  • Lightweight
  • Environmentally friendly
  • 100% recyclable
  • Waterproof
  • Temperature resistant
  • Lasts 50 years

Contact Allied Roofing Solutions for Flat Roof Replacement and Repair in New Jersey

When you need to repair or replace a flat roof, call the team at Allied Roofing Solutions. Our professional and knowledgeable staff are there to guide you and perform high-quality work. Serving homeowners throughout New Jersey, we provide work on all types of roofs. We can repair, replace, and inspect your roof in Bergen County, Essex County, Hudson County, Middlesex County, Morris County, Passaic County, and Somerset County.

Call us today at  (201) 773-0633 or fill out our easy-to-use contact form to get started on a superior roofing system for your home.