Built-Up Roof Vs. Modified Bitumen: Which One Is the Best for Commercial Building

Posted on October 13th, 2021 by Applied Roofing Services

Built-up and modified bitumen roof systems are usually designed for low slope or flat roof structures. While both can withstand harsh weather conditions and harmful UV rays, the two are different in terms of design, application, advantages, and life expectancy.

Read on to learn more about these roofing systems and evaluate the best option for your commercial building.
built up roof

Built-Up Roof Systems

Also known as tar and gravel roofs, built-up roof systems are made of alternating layers of bitumen (asphalt) and reinforcing fabrics. The top layer of the roof is finished with stone or gravel coating to create a continuous sealed surface.

Modified Bitumen Roof

This is an asphalt-based roofing system designed with two layers, namely a base sheet and a cap sheet. While the cap sheet is torched down, self-adhered, or cold-adhered, the base sheet is self-adhered to the roofing substrate.

Modified bitumen BUR can be of two types,

  • Styrene-Butadiene-Styrene (SBS)– Being elastomeric, it can stretch to provide greater flexibility (contraction and extraction capabilities).
  • Atactic Polypropylene (APP) – Being plastomeric (made flexible with elastic plastic) means it can resist harmful UV rays, improving your roof’s stability with time.

Pros and Cons of Flat-roofing Systems

There are 3 types of flat roofing systems for commercial buildings – modified bitumen roofs, single-ply roofs, and built-up roofs. Therefore, it is essential to evaluate the advantages and disadvantages of each roof type to make the right decision for you.

Roofing System Pros Cons
Built-Up Roof
  • Fire resistant
  • Looks appealing
  • Cost-effective
  • Very heavy
  • Requires professional installation
  • Gravel can clog scuppers and gutters
Modified Bitumen Roof
  • DIY installation is possible
  • Energy efficient
  • Inexpensive
  • Not tear-resistant
  • The torch-down application creates a fire hazard
Single-Ply Roof
  • Tear and scuff resistant
  •  Easy to install and repair


  • Expensive
  • Susceptible to punctures

Built-Up Roof System and Other Options for a Commercial Roof

There are two main types of built-up roofing systems, including:

  1. Modified Bitumen BUR

Made of rubber and asphalt, this roof is finished with gravel on top. The modified BUR can be installed on the roof deck using adhesives.

Modified bitumen BUR roofs have three layers, including:

Base Asphalt Layer

This acts as a primary waterproof layer and is modified with synthetic rubber to create a uniform matrix. While strengthening the asphalt, the synthetic rubber improves puncture resistance and elasticity.

Ply Sheets

These sheets can be made of plastic core materials, felt, reinforced fabric, polyester, or fiberglass. They offer weather resistance, stability, and tensile strength to the final finished roofing structure.

Top Surface

While protecting the lower layers from rain and debris, the top surface holds and releases sunlight to prevent moisture and heat damage.

  1. Ballast Roofing

A ballasted roof has a loose-laid bottom-most sheet on the roof deck that separates the roof membrane from the decking material. Though not adhered or anchored, the top layer of the roof is ballasted with gravel stones to keep the roof membranes in position.

In order to prevent excess movement, roof membranes are fastened at certain places on the deck. While providing an aesthetically pleasing look, the ballast roof remains durable by contracting and expanding during cold and hot weather. These roofs are also fire-resistant, energy-efficient, and easy to repair.

What Are Built-Up Roof Systems Made of?

A built-up roof system is made of three layers:

Base Sheet

The asphalt in the base sheet is fastened to the insulation or roof deck to prevent blisters (soft bubbles) and allow vapor movement. You can use industry-standard fully adhering base sheets to prevent the membrane from tearing.

Roofing Felts

These are reinforcing fabrics (organic mats or fiberglass) that increase the roof’s durability while resisting thermal shock and moisture.

Surface Layer

The surface layer with stone, gravel, or mineral granules is finished with aluminum roof coatings, hot asphalt, or elastomeric sealants to withstand dampness and UV rays.

Built-Up Roof System – Repair and Maintenance

Generally, BUR roof systems are prone to the following defects:

  • Cracks – Small cracks may form on the roof surface due to asphalt shrinking.
  • Blisters – Moisture can cause soft bubbles in the roof membrane.
  • Damages – Thermal expansion or detached insulation can damage the roof.

Regular roof maintenance by a professional roofing contractor can help detect these repairs before they aggravate. This way, you can fix the repairs on time and maintain your roof in top condition.

Built-Up or Modified Bitumen: Which Is Better?

While both roof types have advantages and disadvantages, deciding which one is the best for your commercial property depends on your requirements, the building’s condition, and your roof’s pitch.

Therefore, consider hiring a commercial roofing contractor to determine the best roof for your building.

Why Choose Applied Roofing as Your Commercial Roofing Contractor?

With over two decades of experience in the roofing industry, our team at Applied Roofing Services specializes in commercial flat roofing systems, low slope roofs, and green roofing solutions. All our roofing systems are of high quality, ensuring low maintenance and durability. We also have experienced and highly trained roofing professionals who can install your commercial roof in an efficient and non-intrusive manner.

If you are looking for the best commercial roofing contractor in California for installation, repair, and maintenance services, contact Applied Roofing Services today at 714-632-8418 or get a quote online.

About Applied Roofing Services

Applied Roofing Services is a full service roofing company located in CA. We offer durable and high quality residential and commercial flat roofing. We provide roof installation as well as roof repair services, roof maintenance and inspection services. We specialize in low slope roofs, energy efficient, zero maintenance, and green roofing. We have 20+ years of experience in the roofing industry.

What You Need to Know about Modified Bitumen Roof Systems

Posted on August 25th, 2021 by Applied Roofing Services

If you are looking for a long-lasting roofing system for your commercial building, consider modified bitumen roof systems. While being a great choice for flat or low-sloped roof structures, modified bitumen roofs also provide the same level of protection as built-up roofs.
modified bitumen roof systems

Modified Bitumen Roof Systems: Overview

Modified bitumen is an asphalt-based roofing system designed to withstand harsh weather conditions and harmful UV rays. It has two layers, that is, a base sheet, and a cap sheet. The base sheet is mostly self-adhered to the roofing substrate, whereas the cap sheet is cold-adhered, torched down, or self-adhered.

Factors to Consider Before Installing Modified Bitumen Roof Systems

Tools Required

Certain tools are required to install self-adhered modified bitumen roofing systems, such as:

  • A caulk gun to apply adhesives
  • A weighted roller to press the membrane in place
  • A seam probing tool to inspect gaps
  • Appropriate trowel to apply adhesive to flashing details instead of a hot air welder

Also, when priming a long-handled (standing) roller in cold weather, use a hot air welder instead of a trowel, unless instructed otherwise by the manufacturer’s guidelines.

Roofing Applications

Consider the client’s location, needs, and building code requirements. Generally, new building codes insist on the use of self-adhering products due to their environment-friendly installation. Self-adhered roofing systems can be quickly installed even during working hours with little disruption. Therefore, they can be installed on any commercial facility that prioritizes client comfort, including healthcare centers, schools, restaurants, offices, apartments, care centers, etc.

Modified Bitumen Roofing’s 5 Layer System

Modified bitumen roof system’s framework features a five-layer combination of roofing components. These are:

  1. Insulation – Provides an “R” value (resistance to heat flow) for stabilizing the roof’s temperature
  2. Adhesive – This can be hot or cold adhesive made of a bonding agent and waterproofing material
  3. Modified Bitumen Membranes – Made of co-polymer with fiberglass or polyester reinforcements
  4. Surfacing – Protects against weather-related damages and UV rays
  5. Modified Base Sheets or Piles –Waterproof layers that make up the foundation for flat roofs

Benefits of Modified Bitumen Roof System

  • Tear-resistant

Modified bitumen roof systems made of fiberglass and polyester reinforcement layers are the best choice for low-slope roofs with high foot traffic, such as rooftop cafes.

  • Flexible

Modified bitumen roofs have flexible roofing materials, helping them withstand temperature shifts, short-term force or shock, and expand and contract without losing their shape.

  • Waterproof

Being made of several layers of fiberglass mixed with polyester, modified bitumen roofs are capable of resisting water.

  • Energy-efficient

The top layer of the roof can be treated to include “cool roof” features, such as solar reflectance (to reflect sunlight) and thermal emission (to release absorbed heat). This may reduce your building’s cooling requirements, contributing to lower energy consumption.

  • Easy to Repair and Maintain

If damaged or torn, bitumen patches can be used to quickly and efficiently repair the roof. Generally, low-slope roofing seals and flashing are prone to damages, but you can easily prevent such damages with professional installation and regular maintenance.

Rolled Roofing Vs. Modified Bitumen

Factors Rolled Roofing Modified Bitumen
Weight Light-weight budget roofing material Heavier roofing material
Life Expectancy 6 to 10 years (with an average of 8 years) 10 to 16 years
Installation Usually face-nailed in place, with the nail heads being exposed and visible, making them prone to leaks Fully adhered with a cold adhesive applied to the layer below the roof or secured in place by heating with a propane torch
Application Suitable for porches, barns, and sheds, but not feasible for re-roofing a house or for a roof with a pitch below 2/12


Suitable for any building with a minimum slope or flat roof structure

Note that both roofing systems look similar from a distance, with tiny rock granules on their surface for UV protection.

What Makes Bitumen Roofing Special?

Modified bitumen roof’s co-polymer roofing membranes help it withstand high and low temperatures, making it a robust commercial roofing system. Besides, it is a low-maintenance roofing system, so basic care and maintenance are sufficient to keep the roof in its best working condition. A modified bitumen roofing system is also versatile, as more polymer sheets can be added to enhance their elemental and physical durability.

Are Modified Bitumen Roof Systems the Best Roofing System for Commercial Buildings?

A modified bitumen roof system is undoubtedly the best roofing system for commercial buildings due to its energy efficiency, flexibility, and weather-resistant capacity. When properly installed and maintained, a modified bitumen roof will be your building’s most durable and priceless asset.

If you are looking for the best commercial roofing company in California for roofing maintenance services, contact Applied Roofing Services today at 714-632-8418 or get a quote online.

About Applied Roofing Services

Applied Roofing Services is a full service roofing company located in CA. We offer durable and high quality residential and commercial flat roofing. We provide roof installation as well as roof repair services, roof maintenance and inspection services. We specialize in low slope roofs, energy efficient, zero maintenance, and green roofing. We have 20+ years of experience in the roofing industry.

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