Types of Low-Slope (Flat Roof) Options

August 24, 2022by Nick

Do you have a low-slope roof on your home? When it comes time for replacement, you’ll have several options to consider when selecting a roofing material. Before you get started, it helps if you understand the basics of roof pitches and what type of roofing is appropriate for your home. In this blog, we’ll tell you all about low-slope roofs and some of the roofing options available when you need a replacement.

What Is a Low-Slope Roof?

While no roof should be completely flat to allow for proper drainage, a low-slope roof is often referred to as a flat roof. They are nearly flat with a slight pitch, but they are not steep enough to put shingles on. When you need to replace a low-slope roof, you will need a low-slope roofing system with slopes between 2:12 and 4:12 of the run.

What Is a Roof’s Pitch?

Your roof’s pitch is a ratio between the number of inches or feet it rises upward for every 12 inches or feet it extends across. So a roof with a 4/12 pitch will be 4 inches or feet up for every 12 inches or feet out.

A typical steep-slope roof uses gravity so the water over pour the breaks and fasteners in the shingles until it flows off the roof. Gravity can’t help a low-sloped roof or flat roof to drain properly, so the roof needs a watertight membrane that extends to the drains or edge of the roof.

Traditional low-slope or flat roofs were constructed with built-up tar and gravel.

This type of roofing raises many cost, performance, and environmental problems. Today, low-slope roofs are covered with a continuous membrane that is applied to the roof in sheets and bonded with adhesives or heat welding. This helps protect your roof from standing water. Another option for low-slope or flat roofs is metal roofs of copper or tin, though these materials are pricier than using a water-tight membrane.

Since low-slope roofs are harder to drain than steep-slopes where gravity is doing the work, the roofing materials for both types of roofs are not the same. While asphalt or slate shingles look great, they won’t work for your low-slope roof because they do not drain well which can cause a host of problems. However, there are many suitable alternatives for low slope roofing.

Low-Slope Roofing Options

There are five commonly utilized roofing systems for low-slope roofs. Here’s a rundown on their features and where they perform best.

Built-Up Roof

Built-up roofing membranes are made with bitumen and felts. The membranes are laid out on a base sheet fashioned to the roof. BUR roofing is used less today as we have so many more efficient and environmentally sound options.

Modified Bitumen

Modified bitumen is strengthened by adding polymers like Styrene-butadiene (SBS) or atactic polypropylene (APP). These substances give bitumen rubber-like properties. The asphalt is modified for flexibility and built over a heavy fiberglass or polyester base for sturdiness.

Then, the modified bitumen sheets are attached with adhesive and heat.

Polyvinyl Chloride

PVC low-slope roofs are a common feature in restaurants. PVC is also bendable and will cool your house during summer because it conducts heat poorly.

Thermoplastic Polyolefin

Thermoplastic Polyolefin (TPO) is usually a white, one-ply membrane. It is lightweight, chemical-resistant, and has robust impact resistance. TPO low-slope roofing systems are used often in commercial industries. Homeowners love TPO membranes because they reflect heat and keep the home’s interior cool.

Ethylene Propylene Diene Terpolymer (EPDM)

EPDM rubber roof systems are fastened to an insulation board. The rubber covering can also be attached using boulders or ballast. EPDM rubber roof systems are usually black, although white is also available. This type of roof can be used in climates with both hot and cold weather.

EPDM, PVC, and TPO can all be used for residential roofing. Consider the appearance that you want and what rooms are below the roof. If you can see the roof out the windows, you’re probably better off avoiding the white membranes because you will be able to see when it starts to weather or become dirty.

Schedule a Consultation

If you want to learn more about replacing your low-slope roofing, call the pros at SJ Roof. Our experienced team of roofing professionals can help you select a roofing system that meets your needs and looks great, and we guarantee a high-quality installation.  Contact us today for a free consultation and estimate.


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