Five Commercial Flat Roof Systems Explained – Watch Video

This Video Explains about the Three roofing systems – TPO. EPDM and Modified Bitumen Torch Down

Five Commonly Used Flat Roof Systems 

There are 5 types of commercial flat roofing systems commonly installed:

  • Built- Up Roof (BUR) also known as the “Hot-Tar-and-Gravel” Roof System
  • Metal Panel Roof System
  • *2 Ply Modified Bitumen Torch Down Rubber Roof System
  • Single-ply membranes such as TPO, PVC and EPDM Systems
  • Spray polyurethane foam-based Roof System.

*Commercial Roof USA specializes in the installation of 2 Ply Modified Bitumen Torch Down Rubber Roof System.

This is a BUR system also known as a Tar and Gravel roof.

Built-Up Roof Systems (BUR)

The BUR system has been in use in the U.S. for over a 100 years. It is commonly referred to as a “Hot-Tar-and-Gravel” Roof System. These roofs are composed of layers of saturated asphalt paper and moped down hot liquid coal tar or asphalt. Saturated paper is layered in a criss-cross pattern, and depending on the contractor, as many as 12 layers of paper and coal tar or asphalt can be used during the installation.

Coal tar or asphalt is heated in a kettle with propane gas and pumped up to the roof top. Hot tar is spread over the work surface with a mop or squeegee, and the felt paper is rolled out over it.

Asphalt is a petroleum product refined from crude oil and coal tar comes from the distillation of coal. Either way, the coal tar or asphalt is the adhesive, that when combined with many layers of felt paper, forms a thick membrane that becomes the roof.

After the membrane has been built-up, a thin layer of coal tar or asphalt is mopped over the entire roof and aggregate stone of 1/2” is spread over the entire membrane. This stone is used to protect the roof from harmful UV rays.

The “Build Up” has “Come Down”

The BUR roofing system can last many decades, but beyond that, there will be a certain amount of degradation. Petroleum based products will become dry and brittle and start to crack, due to evaporation, causing leaks.

The BUR roofing system is expensive to install, due to the labor and materials involved. These roofs have been known to last for over 50 years, because of the multiple layer “build up.”  Some of them have had as many as 15 -20 layers of paper and tar, however, we have also seen that some contractors would “come down” with the number of layers, to as many as 5 and to as few as 3.

Metal Panel Roof Systems

The Structural Metal Panel Roof System is a type of metal roof system used for a low slope application. It is common to see metal panel roofs over warehouses and factories. The metal panels can span up to 4 ft., from rafter to rafter and can support the weight of a person. A special sealant is used between seams and overlapping joints to prevent water from entering. Neoprene washers are used where bolts fasten the metal roof to the metal rafters. These metal panels are excellent water barriers and will prevent water from leaking through when correctly installed. This type of roof can last for 40 to 50 years, when properly maintained.

Metal roofs systems can be repaired.

Modified Bitumen Membranes

The Modified Bitumen Torch Down Rubber Roof System (MB) was developed by the Italians in the 1960s and made its way to the U.S. by the late 1970s. The rubber membrane is made of reinforced fabrics covered with asphalt, which consists of modifiers that give the asphalt its elastic properties on both sides. The modified asphalt is manufactured in widths of 36″. Because of the rubberized technology, these membranes are referred to as rubber roofs or rubber membranes.

There are 2 Types of MB Rubber Roof Membranes:

APP – is a Modified Bitumen membrane that is fully torched down to the fiber base, and the torch is also used on the seams, hence the name – Torch Down Membrane.

SBS – is a Modified Bitumen membrane that uses cold or hot mopping tar or asphalt adhesives. Some SBS membranes are self adhering; the backing is very sticky, and will adhere to the surface it is rolled onto.

The MB membranes have 3 types of surfaces: smooth surface, mineral surface, and a foil laminate surface. The minerals of the surface have been coated with a ceramic material that protect the rubber against harmful UV rays.

The MB roof system is typically installed as a single-ply system, however, we specialize in a 2-ply system to extend the roof life to 40 years or more. We have come to specialize in this roofing system for many reasons, but the most important one, is in terms of maintenance, because the Modified 2 Ply Bitumen Torch Down Rubber Roof System, needs minimal to none.

Single-Ply Membranes: EPM, TPO, and PVC

EPDM, TPO, and PVC are single ply synthetic membranes, and are manufactured in wide sheets. These membranes are very thin and come in rolls from 8 – 20 feet widths.

Adhesives are used to adhere these membranes to the properly cleaned substrate. If the substrate is not properly prepared; removal of dust and particles, according to manufacturer’s instructions, the adherence is compromised, and the life of the roof is reduced.

EPDM is made from 2 compounds that are derived from oil and natural gas and the seams are glued together with a liquid adhesive that has been reformulated 4 different times. Currently, as a remedy, a new self-adhering cover tape is placed over the seams. These membranes are not well protected from harmful UV rays and are prone to degradation.

The Image below is a Modified Bitumen Torch Down Rubber Membrane with Embedded Ceramic Granules for UV Protection

The image is an example of a 2 Ply Modified Bitumen Torch Down Rubber Roof System.

The Image Below is a White TPO Vinyl Roof with Little UV Protection.

A White TPO Vinyl Roof with Little UV Protection.
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Different flat roof systems explained

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