Commercial roofing is usually flat, and flat roofs require different materials than those with high slopes. While there are nearly a dozen different systems to choose from today, only a few make up the majority of all commercial roofing projects. Modified bitumen materials and built-up roofing systems account for most new roofs and re-roofing projects alike.
Making a choice between a built up roof vs modified bitumen requires a consideration of the features of both options. Each one is better for certain buildings and purposes, so you have to match the material to the roof for the best results. Get the information you need to make an informed choice before your new roofing or re-roofing project with Delta Innovative Services.
What is Built-Up Roofing?
Also known as BUR for short, this flat roofing option involves the application of multiple layers of material. This creates a leak-resistant covering that can handle the shrinking and expanding of the material from shifts in temperature. Layers of synthetic fabric are sandwiched between hot-mopped bitumen, then a surface layer is added to protect the whole assembly.
Insulation is often included under the roofing layers to improve the energy efficiency of the commercial building. Gravel is the material most commonly used as the surface covering for this kind of flat roof, which comes with its own advantages and challenges.
What is Modified Bitumen Roofing?
This type of flat roofing also relies on bitumen to cover and seal the roof, but it’s applied a little differently. It’s applied as a pre-made roof covering that is composed of asphalt membranes combined with polymerized rubber to prevent cracking. Fiberglass is also added to most products to protect the surface and add some rigidity to the material.
There’s no need for hot mopping, but torches are used for some installations to heat the bitumen and seal the rolled material together along the seams. This assembly is similar to BUR in many ways, but was developed as an improvement on that time-tested form of flat roofing.
Built Up Roof vs Modified Bitumen: Comparing the Details
Both of these commercial flat roofing options can work well for retail buildings, warehouses, manufacturing facilities, and other similar structures. The key is finding the right fit based on the structure’s ability to bear weight, the kind of durability needed, and any aesthetic considerations.
Installation Challenges
There are a few challenges unique to each type of material. For example, the fire hazards from the modified bitumen roof installation process must be managed with care to avoid damage to the rest of the structure. On the flip side, built-up roofing materials are heavy and hard to transfer to the top of the building. It’s all up to the unique location and how the structure affects the installation of the roofing materials. Some roof decks will work best with modified bitumen while others will require the extra flexibility of BUR installation. There are alternatives to torch installation for modified bitumen, but cold mopped adhesives and peel-and-stick materials may not work for all commercial roofs.
Appearance
When it comes to appearance, modified bitumen roofs tend to offer greater flexibility in design. BUR systems tend to mostly look the same, although you may be able to choose a specific gravel cover to adjust the color and texture. Of course, most flat commercial roofs are minimally visible from the ground. You can likely work out other features like edging and cornices to further disguise the appearance of the flat roof, eliminating the need to pick a particular material on aesthetics alone.
Cost
The cost of installing a new commercial roof depends largely on the size of the building and the complexity of the system. In most cases, BUR products cost slightly less than modified bitumen installations. Choosing BUR can save you mostly on material costs, although there may be a higher labor cost. However, extra layers or complex installations can quickly make BUR the most expensive choice. It’s best to get a custom quote based on your facility’s size, height, and other details to determine which material will offer the best combination of cost and quality.
Weight
Aside from the weight of carrying the materials up to the roof, each roofing option adds to the amount of support needed for the structure. Heavy roofing materials put stress on the structure, requiring extra reinforcements to support the changes.
If you’re re-roofing an existing building, you definitely need to consider the weight of each option before making the choice. Modified bitumen materials tend to weigh about 2.2 lbs per each square foot. In contrast, BUR systems can range from 5 to 8 lbs per square foot. It largely depends on the number of layers required to protect the roof. It’s much easier to retrofit modified bitumen materials for a re-roofing project because of the light weight, but most commercial buildings can likely handle the weight of a BUR installation as well.
Durability and Longevity
With care, a BUR system can last up to 20 years. The average modified bitumen material installed on a flat commercial roof tends to last around 10 to 15 years at the most. That means you’ll spend more to replace modified bitumen materials in the long run. However, the easier installation process thanks to lighter materials may balance out the need for routine replacement. It’s essential to top up the gravel coating on the BUR system over time to ensure that the material isn’t prematurely damaged by exposure to weather and UV rays from the sun.
Maintenance
It’s relatively easy to inspect modified bitumen roofing yourself, but only roofing professionals can assess a BUR installation and determine its condition. Due to the protective coating over the surface, it’s also harder to find leaks and make repairs on a BUR system. However, both types of roofing generally require thermal imaging and other advanced techniques to trace the source of the leak. That’s just a common concern with most flat roofs. Making repairs is generally equally challenging for a built-up roof and modified bitumen.
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No matter which material you choose, Delta Innovative Services is ready to help you install it in the Kansas City area and beyond. We specialize in responsive service and delivering the peace of mind you need. Contact us today to get started!