A built-up roof on a commercial property.

Should You Get a Built-Up Roof? Pros & Cons

Built-up roofs (BUR roofing) are a time-tested commercial roofing option, but that doesn’t mean they may be the best option for every roof.

BUR roof systems are a modified version of asphalt roofing invented in the 1800s. They became popular for commercial buildings during the 1970s. They’re still around today for a reason. They’re durable, cost-effective, and long-lasting.

But built up roofing does come with some drawbacks. Before you decide to install a BUR system, it’s important to consider how it compares to other roofing materials.

How Do Built-Up Roofing Systems Work?

Built-up roofing systems are made of layers of asphalt and other materials such as bitumen and reinforcing fabrics. BUR roofing membranes are most commonly used on low-slope roofs or flat roofs.

When installing a BUR system, there is a layer of bitumen, which includes asphalt, coal tar, or cold-applied adhesive that is placed across the roof deck. (If necessary, you can fasten a base sheet before putting this layer on to create a safe and sturdy space to work.)

As it’s covered ply sheets (or roofing felts) of hot asphalt and tar fabric or fiberglass are rolled down. These are typically referred to as “plies.” On the top layer, the surfacing aggregate is then placed for durability and aesthetics. Additionally, a reflective roof coating can be added to meet cooling requirements.

Because of the several layers of bitumen involved, not only are BUR systems extremely durable (providing high resistance to fire and wind), but they’re also quite heavy.

Built-up roofing solutions also have high reflective qualities (when a reflective coating is utilized), helping to save energy costs and keep inside temperatures consistent.

Built-Up Roofing Advantages

This popular roofing solution has been around, albeit in less technical form, for ages. Commercial buildings benefit the most, and high-rises around the world use built-up roofing as a viable and efficient roofing solution.

Why? Here’s a short list:

  • Excellent waterproofing
  • Efficient use of space
  • Ultra-violet protection
  • Fire-resistance
  • Low-maintenance
  • Less costly than other systems

Durable Against Harsh Weather Conditions

While you might not typically think of tar as being flame-resistant, it takes a lot of heat to cause it to ignite. Along with that, the tightened layering of the bitumen creates a waterproof roof resistant to penetrations that helps to stop water from finding its way into the building.

With the added aggregate and fiberglass, BUR roofing makes for a very sturdy material. Because it’s so sturdy, you can be assured that your roof will be able to withstand even the toughest weather conditions and climates.

Low Maintenance Roof Membrane

Built-up roofing is typically praised as being a low-maintenance option. Still, many owners opt to inspect the system 1-2 times a year to ensure that the bitumen roof is up to standard.

That minimal upkeep, along with its lower costs, makes BUR roofing an excellent choice for building owners who need a roof installation that won’t break the bank.

Energy Efficiency

Today, most built-up roofing systems come with a layer that has high reflectivity. This creates protection against UV rays, helping to maintain a cool building temperature. As a result, you’ll need to run heating and cooling less often, resulting in improved energy consumption.

Built-Up Roofing Disadvantages

Everything has a downside, and BUR roofs are no different. While maintenance is definitely on the low side, it isn’t nonexistent. Some common things to look for during your seasonal commercial roofing inspection are:

  • Cracks
  • Susceptible to ponding water
  • Blistering
  • Undulations or waves cross the roof surface
  • Open or split joints
  • Difficult installation

These common problems are easily preventable with routine inspection and quick attention from a trusted commercial roofing contractor. Let’s take a quick look and break down some of these common issues.

Split Joints

Open or split joints are where two rolls meet and the seam between them has dried out and separated. The best fix is a replacement, but a more economical path would be a repair using a patch. A qualified professional can assess the situation and determine which option is best – repair or replacement.

Ponding Water

Ponding water is a small problem that can cause enormous issues down the line. Inspecting your BUR roof after strong weather (to check for water pooling or other problems) is a great preventative measure.

Gone unchecked, your commercial roof can crack or leak, which can encourage soft spots and other warping problems, like waving, undulations, and blistering.

Blisters

Blisters are often caused by water damage, possibly from too much moisture on the underlayment during installation or a small leak that has gotten worse. On a hot day, the water expands as it turns to steam, forming blisters. There could be one or many, but it’s always a bad sign, as it makes the top layer susceptible to tearing with foot traffic.

Difficult Installation

The torch-down method of installation used to adhere a BUR roof can be dangerous. If handled incorrectly, it creates a fire hazard. When you choose to install a BUR roof, make sure that you contact a reputable roofer who can handle the material.

All of these things should be dealt with immediately by inspecting the roof inside and out for more than surface damage.

If replacement is necessary, BUR roofing requires that no people are inside the building during the roofing process. This downtime can be costly. Thus, proper inspection and maintenance cannot be stressed enough. Most problems are not critical if they’re dealt with in a timely and professional manner.

How it Compares to Other Roof Types

Depending on what you want out of your roof, BUR may be the best option due to its durable nature. But you have a number of options when it comes to flat roof systems to consider before you make your final decision.

Metal Roofing

Metal roofing and BUR systems are both durable. BUR may be more waterproof than a metal roofing system with exposed fasteners. BUR’s upfront costs are also lower than a metal roof installation.

However, metal roofing systems last much longer than BUR. BUR’s lifespan is around 20-30 years, while a metal roof can last 70 years or more.

EPDM

EPDM, a single-ply roofing system, also has a longer lifespan than BUR. It can usually last around 30 years. But like metal roofing, it’s a little more expensive. Roof repairs are easier with EPDM, but you may need more of them. EPDM is less resistant to punctures. It also offers less energy efficiency than BUR.

Modified Bitument Roofs

Another type of asphalt roofing, modified bitumen roofs have an easier installation process than BUR. Modified bitumen has two layers: a cap sheet that is torched down or self adhered to a base sheet that is adhered to the substrate.

It comes in two types – styrene-butadiene-styrene (SBS) and atactic polypropylene (APP). Both are elastomeric, so they’re flexible and resist UV rays. Both are cost-effective options. However, modified bitumen roofs aren’t as tear resistant.

TPO

TPO offers higher energy efficiency than BUR, so it’s more popular in hotter climates. It’s also less likely to crack in colder ones. However, it is more expensive and less resistant to high-traffic. Also, improper installation of TPO can lead to leaks.  Both TPO and BUR have similar lifespans.

PVC

PVC is more durable than BUR and typically lasts 30 years with the right maintenance. It offers superior chemical resistance, so it’s good for industrial applications. However, it does come with a considerably higher cost, and is much more difficult to repair, so BUR is the better choice if you have budget constraints.

Built-Up Roof Systems In a Nutshell

BUR industrial and commercial roofing systems are a great solution for flat roofs, as long as you know what to look for (and know why you’re getting it).

As with most things in life, there are pros and cons. Compared to many other roofing materials, it doesn’t last quite as long. However, if you’re facing budget constraints while looking to replace your existing roof, a built-up roof is a great option. The installation process can be dangerous, however, so make sure you partner with reputable roofing contractors.

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