What Is a Built Up Roof?

By Karen L Edwards 10-20-2020
QUICK SHARE
Tag Icon

A built up roof system is a popular choice for buildings with low-slope or flat roofs. Often referred to by the acronym BUR, this system has been used for 100-plus years in the U.S.


What makes BUR systems so popular? They are known for providing excellent protection due to their redundant nature because they are made up of multiple layers of ply sheets and asphalt. These layers are then topped off by a cap sheet or a flood coat of asphalt and granules. The multiple plies provide resistance to weather and heavy-duty protection for the building.


Components of a Built Up Roof System


Built up roof systems can be constructed in a variety of ways. Often, the built up roof system starts with a base sheet installed over the polyisocyanurate (polyiso) insulation or cover board, typically through the use of mechanical fasteners. The base sheet serves as the bottom layer of waterproofing protection for the roof system and provides a surface that will allow subsequent sheets to be adhered with hot asphalt.


A layer of asphalt is applied over the base sheet for the installation of reinforcing felt, sometimes called a ply sheet. Many people picture kettles of hot asphalt being mopped onto the base sheet in order to install the ply sheet, but advances in manufacturing have created alternative options. For instance, contractors can choose to use cold-applied adhesive solutions instead of hot mopping asphalt and kettles.


When saturated in asphalt or cold-applied adhesive, the reinforcing felt creates a barrier that provides additional resistance to water intrusion. The process is repeated with the application of asphalt or cold-applied adhesive, followed by the installation of additional plies until the desired number of plies is achieved. The system is then either capped with a mineral-surfaced cap sheet or topped off by covering the top layer with asphalt and spreading gravel or slag.



This video provides an easy-to-understand look at the layers that make up a typical four-ply system.


Benefits of Built Up Roofing


Built up roofing owes its popularity to a number of benefits it provides, including:



  • Time-tested technology. It's hard to argue with more than 100 years of history.

  • Redundancy. Built up roofs provide many layers of protection, so if the top layer is damaged, the additional layers below will continue to protect the building from water intrusion.

  • Guarantees/Warranties. BUR systems may be eligible for guarantees or warranties of up to 20 years, depending on the materials used and the system installed. Check with the manufacturer for guarantee/warraaty requirements and coverage.

  • Reflective cap sheets available. White-coated cap sheets are availableto help reflect the sun's rays away from the building, which can help lower internal termperatures.


There are many options when it comes to choosing an asphaltic roofing system, each with different benefits. When choosing your system, the best place to start is by determining the characteristics you want in the roof. You can review this brochure to see a comparison of the different products, learn about their features, and browse available guarantees. Of course, you can always talk to GAF to help you find the best solution.

Don't miss another GAF RoofViews post!
LATEST UPDATES
Companies, organizations, and firms working in the building, construction, and design space have a unique opportunity and responsibility. Collectively, we are contributing to nearly 40% of energy-related carbon emissions worldwide. While the goals, commitments, pledges, and promises around these challenges are a step in the right direction, no one entity alone will make major improvements to this daunting issue.
Mark Rutherford is one of the founders and current co-owner of Atlanta Roofing Specialists, where he's responsible for production and commercial sales. The company provides new roofs and repair services for residential and commercial buildings in the Atlanta area, and has been a part of the community for 30 years.
As the warmer temperatures of spring arrive, you might be getting out your vacuum, mop, and household cleaners. But the outside of your home likely needs some attention too. Signs of winter damage often show up once the snow melts and the ground thaws, so now's also the time for outdoor spring cleaning. Proper home maintenance—such as inspecting your roof and other areas of your home that might need repair can help preserve your property.
What's old is new again. In addition to musical tastes and clothing trends, this is often the case with certain architectural styles. Today, the modern mansard roof is experiencing a comeback. The first known use of this roof style was in 1550 where it appeared on a portion of the Louvre Museum in Paris, France. The mansard roof derives its name from François Mansart, a French architect who favored the style and used it in many of his building designs.
If you're thinking about replacing your old roof or installing a new one, one thing to consider is whether you should choose darker or lighter shingles. Appearance isn't the only factor this choice affects. Depending on your home and where you live, choosing darker or lighter options might also be more beneficial and efficient. Here's what you need to know about selecting between light and dark shingle colors for your roof.
With any roofing project, there are a number of factors to consider when choosing the right design: sustainability profile, potential risks, overall performance, and more. Our Building and Roofing Science (BRS) team specializes in working with industry professionals to help them enhance their roof designs across all of these areas. Leveraging their building enclosure expertise, our BRS team serves as thought leaders and collaborators, helping design professionals deliver better solutions for their customers.
This blog contains information created by a variety of sources, including internal and third party writers. The opinions and views expressed do not necessarily represent those of GAF. The content is for informational purposes only. It is not intended to constitute financial, accounting, tax or legal advice. GAF does not guarantee the accuracy, reliability, and completeness of the information. In no event shall GAF be held responsible or liable for errors or omissions in the content or for the results, damages or losses caused by or in connection with the use of or reliance on the content.

Interested in sharing or republishing our content? We kindly ask you to adhere to our guidelines.