Flat Roofing

A flat roof is a type of roofing that covers a building. Unlike other sloped roofs, flat roofing is generally horizontal, though not exactly. This is because flat roofing uses a small inclined angle that may unseen by the naked eye to move debris off the roof.

Flat Roofing Basics and History

Flat RoofingFlat roofing is constructed using roofing materials that can provide a surface to drive rain water away. Back in the day, flat roofs would use a tar and gravel approach to cover the area as long as there was no pooling of water, was sufficient enough to prevent water penetration. Unfortunately, these surfaces do poorly in colder climates where ice dams and snow can block the flow of water. In addition, these types of heavy materials may cause the roof to sag and can affect the building structure.

Nowadays, modern flat roofs tend to use specific types of roofing materials and membranes to remove the water. These membranes are applied on top of the roof as a continuous sheet as much as possible with the help of sealants and adhesives. These roofing products are great in that they allow the bonding of multiple sheets and reinforcing parts where it’s penetrating the roof surface. More expensive flat roofing materials can be made from metal like copper and tin. These types of metal flat roofing materials are soldered together with interlocking systems of metal panels. With flat roofing, homeowners can create more living space and also use the surface for other functions to maximize its usage potential.

Types of Flat Roofing Available

Flat Roofing MaterialsIf you have flat roofing, the 4 most commonly used types of flat roofing systems are: Conventional Built-Up Roofing also known as BUR, Modified Bitumen Built-Up (SBS), Thermoset Single-Ply (EPDM) and Thermoplastic Single-Ply (TPO). In addition, those with metal flat roofing can also have the choice of Elastomeric Liquid Systems as well. It is highly recommended that you research on each of the groups, taking into consideration your structure specifics and your plans for use of the roof area. Take into account the weight and support ratio and if the roofing material will be too heavy or not. If there is a substantial amount of equipment mounted above and through the roof, a thicker and more durable roofing system will be needed. Make sure you explore your options and know what you roof will require to satisfy your needs.

Built-Up Roofing/BUR

Asphalt BUR (Built Up Roof) is the arguably the most common type of flat roofing type at this time. It is constructed by multiple layers of reinforcing plies and asphalt. This will form a neatly repeated overlapping of waterproofing layers that will become the roof. The amount of thermal and sun reflection depends on the materials used to fill up the space. The most common materials used are gravel and these roofs are referred to as asphalt or tar and gravel roofs. Because of its durability, it remains a one of the most complete roofing materials for industrial and commercial roofing. The membranes create a great layer above the roof and can help filter out debris for water to run off in a more effective manner.


Modified Bitumen Membrane (SBS)

Torch Flat RoofingThis type of flat roofing is utilizing a very tough and resilient membrane known to everyone as – rubber. The core made out of a strong, resilient, non-woven polyester mat. This is then coated with weather resistant, polymer modified asphalt to give it extra reinforcement. The overall system consists of 2 plies – base and cap. This type of roofing system on average guarantees up to 15 years or more depending on maintenance and weather. There are major advantages to this bitumen membrane roofing as it is cost effective, light weight, and more importantly resilient (as the polyester mat core allows it to resist splits and tears due to it pliability and elongation characteristics).

The 2 types available are:
1) SBS polymer-modified bitumen membranes: It is installed in hot mopping of asphalt (similar to the BUR system) or with cold adhesive. Some SBS modified membranes contain an adhesive backing which make them self-adhering. Finally, SBS modifiers impart a more rubber-like quality to asphalt.
2) APP polymer-modified bitumen membranes are different than those of the SBS mentioned above as this type of roofing are heat-welded or torch-applied. APP modifiers create a plastic-like feel to the quality of asphalt.

It is extremely important to achieve the flat roofing slope of at least 2%. This small incline will help prevent pounding water and the clog up of other debris. At this incline, the roof can be dry within 48 hours after rainfall. If the incline is not done properly, the roof will deteriorate fast as asphalt can break down slowly with water. An important note, as torching is used during installation, always consult with the contractor about liability insurance for “hot works”.


EPDM (Ethylene Propylene Diene Monomer)
is a synthetic rubber most commonly used in single-ply roofing as it is constantly available and relatively simple to install. It is a roofing material available in different thicknesses in 45, 60 and 90 Mm. With high flexibility and durability, EPDM can easily be fabricated and shape itself to the most abstract roof shapes and design. These types of roofing materials are generally sold in sheets from 50′ wide to 100′ long, eliminating the use of seams. There are Black EPDM and White on Black EPDM available to the public. New and more advanced versions of this product have it combine with polyester fleece to reduce shrinking during the change in temperatures. The benefits and advantages include the following: durability, flexibility, recyclable (environmentally friendly), low maintenance with general cleaning, and has a long life span.


TPO (Thermoplastic Polyolefin)
flat roofing systems are made up of ethylene propylene rubber and combines durability of rubber with the proven performance of hot-air weld-able seams. The result creates a very high performance type of product. TPO roofs are beneficial by providing the following: Exceptional resistance to ultra-violet rays, ozone and chemical exposure, extremely heat reflective, is also energy efficient (able to offset up to 50% or more of the original cost to install the roof as a result of improved energy efficiency), environmentally friendly as it’s a recyclable product, algae-resistant, durable from tears and punctures, flexible, fire resistant and do not contain plasticizers – avoiding the problem of plasticizer loss.

These are just a summary and the general benefits of what flat roofing systems can provide. Be sure to contact your local contracting company on how these can be built and note to them what sort of roof you are looking for. Make sure to have them check your current roof status to understand what they’ll recommend and eliminate any potential leaks and damages that can stall the installation and rebuild process.

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