Built Up Roofing Systems

Recognized As The Commercial Standard, Built Up Roofs Are Always A Solid Choice

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What Is Built Up Roofing?

Built-Up Roofing, also called BUR, is perhaps the most common roofing material used on flat or low-slope roofs. It is made up of alternating layers of reinforcing fabric and bitumen and is usually finished with a top layer of aggregate, such as stone or gravel. BUR is preferred for many commercial roofs because it creates a continuous sealed surface.

Repairing Built Up Roofing

As built-up roofing ages, it often requires frequent repairs.  Some of the most common repair requests that we receive are listed below.  Each of these problems should be remedied immediately after detection to avoid any further structural damage to your property.

  • Open joints
  • Blisters
  • Undulations or waves¬†
  • Cracks¬†

If you are experiencing any of the above problems with your built-up roof, please call McCormack Roofing, a licensed, bonded, and insured roofing contractor, to get an estimate for repairs. 

A Proven Track Record

Built Up Roofing is popular with many contractors in Southern California, mainly because of its ease of installation and its adaptability.

Built-Up Roofing Materials

Most Built Up Roofing is comprised of three parts: bitumen material, ply sheets, and one or more surfacing materials. The bitumen can be either ‚Äúhot,‚ÄĚ meaning it is heated so that it liquefies during installation, or it can be ‚Äúcold,‚ÄĚ which is more like an adhesive and is not heated. Cold built-up roofing can be sprayed or applied with a squeegee. It does not give off toxic fumes during application and is not dependent on weather. It also usually offers better performance than hot built-up roofing.

The ply sheets of built-up roofing are special fabrics that are reinforced with fiberglass or organic materials. Each ply sheet layer is laid over hot or cold bitumen to bond it to the roof. Ply sheets are commonly produced in a standard width of about 36 inches.

Surfacing materials create the top layer and typically consist of small stones or gravel, depending on the application. This layer provides a finished look and helps protect the layers below from sunlight and damage from flying or falling debris. It also makes the roof safe to walk on.

Built Up Roofing Longevity

Depending on the climate and the types of materials used, built-up roofing has a typical lifespan of 15 to 20 years, but some applications can last up to 40 years. In general, built-up roofing tends to fare better in warmer climates than in cold regions. This lifespan makes built-up roofing comparable to composition shingles, which last between 15 and 30 years, depending on their quality.  Other roofing materials can last much longer.  For example, standing seam metal roofing can last up to 50 years or longer.   

Weighing The Pros And Cons Of Built-Up Roofing

Built-up roofs tend to provide excellent waterproofing and ultra-violet protection. Because of their top layer of aggregate, they are also fire-resistant.  This type of roofing is also generally low-maintenance. 

On the flipside, built-up roofing can be tedious and time0-consuming to install and, with the exception of cold bitumen processes, installation involves hazardous fumes. Overall, installation costs are relatively high, and some types of this roofing can be susceptible to wind and water damage (much more so than FiberTite for example).  Further, built-up roofing does not offer the same type of Solar Reflectivity of either a foam or fabric membrane application like FiberTite.  And built-up roofing does not offer the insulation benefits of a more modern foam covering.  

Frequently Asked Questions

Because the gravel holds and releases heat, the layer of gravel on a BUR flat roof can both help water evaporate and keep heat away from the underlying roof structure. The gravel provides a better grip for foot traffic when conducting maintenance or repairs.

What is a 4-Ply roofing system? (B.U.R) roof membranes (Tar and Gravel) A 4-Ply roofing system involves roofing felts that are typically four plies composed of layers of reinforcement such as fiberglass or polyester felts, with each ply being embedded in a full bed of hot asphalt/bitumen.

First, we attach base sheets to the roof's subsystem using roofing nails. Then, we use tar, concrete, adhesive, or asphalt to glue down felt over the top of the base sheeting. Next, we install a layer of gravel or cap sheets, which we then cover with a final layer of asphalt.

Flat roofs, which are usually built up with layers of roofing felt and asphalt or coal tar, should be recoated every two to four years, unless they are covered by a layer of gravel or other stone chips.

The three most common Built-Up Roofing types are:

  1. Hot built-up
  2. Cold built-up
  3. Ballasted asphalt built-up

Of these three BUR types, ballasted asphalt is becoming the most popular option for many roofers due to its capability as a fire retardant and the finished surface it provides.

Cold Built-Up Roofing is another solid option, especially for environmentally-sensitive projects.