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The More You Know About Roofing Options, the Better We Can Serve You

Over the years we have received a variety of questions about commercial roofing and industrial roofing issues, the techniques we use, and various materials involved in delivering a hand crafted flat roofing solution. To help explain some of the most commonly asked questions that we receive, we have created this list of FAQs and answers.

If you have any questions that are not answered here,


1. What are the most common causes of roof leaks?

NEW: The most common causes of flat roof leaks are blisters, pressure ridges, bare felts and ponding of water.

2. What is B.U.R., and how does it work?

NEW: Built-Up Roofing (commonly known as “asphalt and gravel” or composition roofing) is the most reliable approach for flat commercial roofing and industrial roofing applications. It was invented in England in the 1840s where it rained a lot. While the materials and technology have evolved, the basic premise remains the same. 

There are 3 basic components in a B.U.R. system – waterproofing, reinforcing and surfacing. Next line: They are either secured using hot asphalt or torch applied:

  • Waterproofing keeps you dry
  • Reinforcing ensures maximum structural integrity
  • Surfacing (most often done  with a top coat of asphalt covered with UV-reflecting aggregate or mineral) keeps the underlying structure protected from water, light and wind. Surfacing is also known as ballasting.
3. What materials are used in B.U.R.?

NEW: 4-ply B.U.R. Systems are typically comprised of 15lb perforated felts and sometimes fiberglass reinforced felts, laminated together with hot asphalt and finished with ⅜’s pea gravel ballast.

Depending on your existing building structure, specific climate related-needs and the extent of your repair requirements, there are a wide range of B.U.R. systems and products Crown Industrial may employ in various combinations to ensure a secure, dry flat roof over your head. The most common options used in B.U.R. systems are:

Modified Bitumen Membrane (MB)

Polymer-modified bitumen or modified bitumen (MB) sheet membranes were developed in Europe in the early 1960s and have been in use in North America since the mid 1970s. Polymer-modified roof membranes are composed of reinforcing fabrics that serve as carriers for the hot polymer-modified bitumen as it is manufactured into a roll material. MB roof system membranes are composed of multiple layers, much like B.U.R. membranes. MB roof systems typically are installed as a two-ply system and almost always are fully adhered. There are two types of MB roofing membranes:

– SBS (Styrene-butadiene-styrene aka “elastic asphalt”)

SBS polymer-modified bitumen membranes commonly are installed in hot moppings of asphalt (similar to B.U.R. systems) or cold adhesive. Some SBS modified membranes have an adhesive backing and are self-adhering.

– APP (Atactic polypropylene aka “plastic asphalt”)

APP polymer-modified bitumen membranes typically are heat-welded or torch-applied. Generally, APP modifiers impart a “plasticized” quality to asphalt, and SBS modifiers impart a “rubberized” quality to asphalt. MB membranes and EPDM, a thermoset membrane, often are confused by consumers because flat roofing companies aren’t always clear in explaining the differences. MB and EPDM membranes are sometimes called “rubber roofs”. Surfacing for MB membranes include aggregate or gravel, mineral surfacing, metal foil-laminate surfacing, and smooth liquid-applied surfacing.

4. What are Single-Ply Systems?

A. Thermoset Membranes

Thermoset membranes are made of materials that chemically crosslink. Once the seams have cured, your flat roof is essentially comprised of one giant sheet of roofing over your business and its people, goods, and equipment. Thermoset membrane options include:

  • EPDM (Ethylene propylene diene terpolymer)
  • CSPE (Chlorosulfonated polyethylene)
  • ECH (Epichlorohydrin)
  • CR (Neoprene)
  • PIB (Polyisobutylene)

B. Thermoplastic Membranes

These membranes are very similar to thermosets but there is no chemical cross-linking or vulcanization. Seams in the materials are welded together with solvents or heat. The welds – when done properly – are as strong as the material itself. The most common types of thermoplastic membranes are:

  • PVC (Polyvinyl chloride)
  • PVC alloys & compounds
  • CPE (Chlorinated polyethylene)
  • TPO (Thermoplastic olefin)
5. What causes flat roofs to deteriorate and leak?

The most common causes of flat roof deterioration and leaks include:

  • Standing water
  • Harsh winter weather
  • UV damage from the sun
  • Lack of general maintenance

These issues can cause blisters, pressure ridges, and result in bare felts that all increase the risk of flat roof leaks.

6. What can I do to extend the lifespan of my flat roof?

The typical lifespan of a well built flat roof is 25 to 30 years. If you are committed to maximizing and extending the lifespan of your flat roof, annual inspections and routine general maintenance are the most effective and readily available tools.

7. How old should my flat roof be before I get an inspection?
At Crown Industrial Roofing, we recommend that all businesses start getting flat roof inspections at the 10 year mark, and continue with annual inspections every year thereafter.

These inspections can help prolong your flat roof’s lifespan, and provide the opportunity for early flat roof leak detection, avoiding costly and time consuming issues down the road as the result of emergencies.

8. What makes Crown Industrial Roofing different that other flat roofing companies in the Greater Toronto Area?

For 40 years, Crown Industrial Roofing have been proud to offer excellent customer service and flat roof services to businesses in the Greater Toronto Area. And we can do that because of our expertise and experience, along with our specific and effective flat roof techniques that separate us from other flat roofing companies in the area. 

Our dedicated team of experienced and professional commercial roofers and industrial roofers are committed to quality work and results for all of our customers, and we back that up with our warranty.

9. What is covered by the Crown Industrial Roofing Warranty?

Crown Industrial Roofing warranties everything that we repair, replace, and install on all flat roofing jobs. We stand by all of our work, which is why all flat roof repair work is backed by a full 5-year warranty, and all flat roof replacements are backed by a full 10-year warranty.