COMMERCIAL ASPHALT ROOFING: BUILT-UP ROOFING(BUR) & MODIFIED BITUMEN(MBR)

Upgrade your facility with durable Built-Up Roofing (BUR) or flexible Modified Bitumen (MBR). Expert installation, superior waterproofing, and 30+ year lifespans. Contact Martin Roofing for a professional asphalt roofing consultation today.
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Built-Up Roofing (BUR): The “Gold Standard” for Longevity

Often called “tar and gravel” roofs, these consist of alternating layers of bitumen and reinforcing fabrics topped with gravel. They offer time-tested durability and superior waterproofing.

Modified Bitumen (MBR): The Flexible Modern Choice

A modern evolution that blends asphalt with rubber or plastic polymers for high flexibility. It is lighter than BUR and highly resistant to punctures.

While both systems provide a rugged, multi-ply barrier for your facility, choosing between them depends on your building’s specific structural needs and your long-term goals. See how they compare side-by-side below

MBR vs. BUR: Key Differences at a Glance

Feature

  • Material Composition
  • Application Method
  • Flexibility
  • System Weight
  • Expected Lifespan

Built-Up Roofing (BUR)

  • Asphalt, felt, and gravel
  • Hot mop, on-site layering
  • Can crack in extreme cold
  • Heavy
  • 30–40+ years

Modified Bitumen (MBR)

  • Asphalt + polymers (rubber/plastic)
  • Torch, self-adhered, or cold-applied
  • Handles expansion/contraction
  • Lighter
  • 20–30+ years

Technical Breakdown: Components of Built-Up Roof vs. Modified Bitumen

A high-quality roofing project begins with the right surfacing materials. In a built-up roof system, multiple layers of bitumen and ply sheets are finished with a gravel or mineral cap sheet to protect against UV rays and foot traffic.

Alternatively, modified bitumen roofs utilize a specialized bur system enhanced with polymers. These commercial roof systems offer excellent energy efficiency by reflecting heat. Regardless of the choice, proper installation on the roofing deck is the most critical factor in achieving a 30+ year service life.

Shared Benefits for Your Commercial Property

No matter which system you choose, both provide high-performance protection for your facility:

Superior Waterproofing

Both systems utilize redundant layers for excellent water protection

Routine Maintenance

Both systems require similar upkeep, such as clearing debris and checking for punctures, to ensure they reach their full service life

Industrial Durability

These roofs are highly resistant to wind, harsh weather, and heavy foot traffic

Which Should You Choose?

Final Comparison: Built-Up Roof vs. Modified Bitumen When deciding on your commercial asphalt roofing, consider these three factors:

  • Installation Environment: If your building has a complex roofline with many penetrations, the flexibility of a modified bitumen cap sheet may be easier to seal than traditional BUR.

  • Climate Resilience: MBR handles extreme temperature fluctuations (expansion and contraction) better than BUR, which can sometimes crack in extreme cold.

  • Weight Constraints: If your roofing deck has weight limitations, MBR is the lighter alternative to the heavy gravel-topped BUR system.

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Frequently Asked Question

How does Martin Roofing ensure a watertight seal for these systems?

For Built-Up Roofing (BUR), we utilize a redundant multi-ply approach where each layer of bitumen and ply sheet is carefully overlapped to create a thick, seamless barrier. For Modified Bitumen (MBR), we focus on precision welding—whether using torch-down, cold-adhesive, or self-adhering methods—to ensure the membrane are perfectly used.

The “best” method depends on your building’s environment. Hot mopping (for BUR) is excellent for maximum waterproofing but requires specific safety protocols. Torch-down (for MBR) provides high flexibility for temperature shifts, while cold-applied adhesives are ideal for buildings where open flames are not permitted.

Modified Bitumen typically installs faster because it comes in pre-fabricated rolls. Built-Up Roofing is more labor-intensive and takes longer due to the multiple layers of “hot work” therefor more expansive. We provide a specific timeline after our initial site inspection.

Yes. Because both systems offer long-term durability. we provide up to 25+ years of professional warranties that cover both materials and our expert workmanship.

If you need maximum longevity and have a building that can handle the weight, BUR is the “gold standard.” If you need a lighter-weight system that offers more flexibility during temperature changes, Modified Bitumen is an excellent choice.

Yes. While BUR can be more difficult to repair because of the gravel layer, both systems can be maintained and patched. Martin Roofing provides professional inspections to identify “alligatoring” or blisters before they become costly leaks.

Yes, asphalt-based multi-ply systems generally offer excellent fire ratings, especially when finished with gravel or mineral surfacing.

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