7 Terms You Need To Understand About Commercial Roofs

Commercial roofing contractors can use technical terminologies which new building owners and managers may not be familiar with. A reputable roofer should help you understand the industry jargon they use when issuing roofing inspection reports or cost estimates.

Our experienced roofing specialists have taken time to piece together this list of common terms used in the commercial roofing industry. Many of them have to do with various commercial roofing materials, but some simply refer to processes. Let’s take a look.

1. Roof Slope

The roof slope or pitch is simply the angle at which a roof slants. It is usually calculated by the number of inches a roofing plane rises vertically for every 12-inch horizontal run. So, a roof with a 4/12 pitch rises 4 inches for every 12 inches of horizontal run.

For commercial roofs, a flat roof isn’t necessarily flat but has a low slope – typically 1/4 inch per foot or less. Any roof (including flat roofs) must have some level of slope to ensure proper water runoff and drainage.

2. Flashing

Flashing refers to materials used to weatherproof and/or seal the edges of a commercial roofing system at places where the covering ends. Flashing is typically installed at the edge of the roof or anywhere the roof is interrupted, such as at drains, expansion joints, valleys, or around rooftop equipment like skylights and HVAC systems.

3. R-Value

Every roof must have some insulation to prevent heat from escaping your building in cold winter months and shield the building from the scorching summer heat. The R-value refers to the thermal resistance of the roofing material or the measure of the material’s resistance to thermal conduction. You need to have the correct R-value of insulation installed in addition to considering the inches it adds to your roof. In practical application, the R-value signifies the specific thickness of the insulating material.

4. Substrate

The substrate is the surface over which the roofing or waterproofing layer is applied. For commercial buildings, the term may refer to the underlayment, the structural deck of the roof, or a cover board depending on the type of roofing system used.

5. Underlayment

Your roof’s underlayment is a felt or sheet material roofers install between the roof deck and roof covering. The primary purpose of an underlayment is to separate a roof covering from the roof’s structural deck and provide secondary moisture and weather protection within the roofing system.

6. Seam

A seam is a point where two panels of roofing material are connected to your roof. A seam must be sealed correctly to prevent leaks. Since roofing materials expand and contract significantly with temperature fluctuations, it is important to design joints and fasteners to accommodate this movement. Otherwise, seams can come loose, allowing joints to open and cause leaks. Your roofer must also use quality sealants or sealing tapes to seal out water, dirt, and other debris which could compromise the integrity of your roof.

7. Materials/Coatings

The final layer on a commercial roof is the roofing material or coating. The most common flat roofing materials and coatings include:

  • EPDM (Ethylene Propylene Diene Monomer) – A durable synthetic rubber roofing membrane used in a wide range of commercial and industrial buildings. It offers extreme durability and cost-effectiveness, making it a popular roofing membrane for flat roofs.
  • TPO (Thermoplastic Polyolefin) – A single-ply roofing membrane which is quickly gaining popularity in commercial applications. It is made up of a single layer of synthetics and reinforcing scrim to reflect sunlight, allowing your commercial air conditioners to run more efficiently. TPO also offers higher resistance to punctures as compared to EPDM.
  • Polyiso Single-ply Roofing Solutions – A rigid foam used in more than 70% of commercial roofs. It offers a long-lasting insulation solution for commercial buildings. Adhesives are often applied to the underside of the membrane as well as the top facer of the insulation for adherence.
  • Built-Up Roofing (BUR) – A highly reliable waterproof membrane is typically field-fabricated with layers of bitumen and alternating plies of reinforcing felts. These redundant layers give BUR roofs exceptional resistance to weather and moisture penetration.
  • Modified Bitumen – This asphalt-based roofing material withstands harsh exposure to extreme environmental elements such as UV rays, snow, and hail.
  • Single-ply Roofing – A wide-width sheeting material installed with far fewer seams when compared to asphalt rolled roofing systems. There is no need for hazardous torches or hot asphalt to install the material. They also come with prefabricated fitting accessories to make the installation easy.
  • Liquid Applied Membranes – A monolithic, liquid-based, fully-bonded coating suitable for commercial roofing installation and waterproofing. The coating cures to form a solid rubber-like elastomeric waterproof membrane. It can be applied over many substrates, including concrete, asphalt, and bitumen.

It’s always important to work with a professional, local roofing contractor to help diagnose any problems with your commercial roof. They can best recommend the right solution for your roof. Still have questions about any other terms? Midwest Roofing Siding & Windows in the Twin Cities is here to help. Contact us today and experience firsthand our legendary roofing services!

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