Flat Roofing – Choosing a Roof Type

If your roof doesn’t appear to have a visible slope to it, you have a flat roof.  Technically, because your roof has to prevent rainfall and debris from pooling on it and leaking into the structure below, it’s not perfectly flat.  It has a series of subtle slopes to it to keep your home or business safely away from the elements.  Therefore, a flat roofing system must completely cover the roof so there are no leaks during the rainy season.  If there isn’t much slope for the water to drain, then that water will certainly find any gaps in your roof’s coverage.

When you’re installing a flat roof, you have a variety of materials and techniques to choose from.  Although California’s energy code (Title 24) requires all flat roofing materials to be white upon completion, due to the nature of flat roofs, we can coat any material with a white finish to save you energy and money.

PVC and TPO membranes can both be installed either mechanically, with hidden plates and fasteners underneath the covering, or by adhering the material directly to the roof’s surface.  Mechanically-attached materials tend to offer more flexible applications, and fully-adhered materials offer enhanced wind resistance.


PVC (Polyvinyl Chloride) Membrane

PVC membranes consist of a single layer of a flat and flexible material.  While the roofing industry recommends a breaking point of 200 pounds per inch, PVC usually clocks in at around 300 pounds per inch, making it a fantastic (albeit expensive) choice.  It’s also more chemical and grease resistant than TPO, making it a good option for restaurants.  It can be attached with hidden metal plates and fasteners, or adhered directly to the roofing deck below, and its seams are welded shut to ensure water resistance.


TPO (Thermoplastic Polyolefin) Membrane

TPO membrane is an extremely durable material.  Many advances have been made in its development over the past few years.  It mostly comes in light, energy-saving colors and its strength is comparable to PVC membrane.  Like PVC, roofers can attach it mechanically with fasteners or manually adhere it to the roof’s surface.  TPO has slightly better tear-resistance than PVC, but PVC is a more flexible material.

Modified Bitumen (MOD-BIT)

Modified Bitumen roofing systems, by contrast, consist of multiple layers of material.  First, your contractor builds up a base level.  Then, they adhere a membrane to the roof’s foundation with high heat.  Finally, they top the whole thing with gravel and a white coating in compliance with the local cool roof laws.  It’s a good option for if you have a roof with a lot of penetrations or varying levels.


Built-Up Roofing (BUR)

Finally, we have Built-up roofing systems, otherwise known as a standard tar and gravel roof.  It’s the cheapest option available, but the alternating layers of bitumen and gravel all add up, making it an extremely heavy material to work with.  You’d need a very strong foundation to be able to adequately support the structure.


If you still aren’t sure which finish is the most well-suited to your project, don’t hesitate to call a professional at Modern Roofing for a free estimate and consultation!

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