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Flat Roofing Systems
Roofs take abuse and require maintenance. Make no mistake about that. Sloping or pitched roofs help shed water and minimize snow build up. As a result, sloped roof systems like asphalt shingles, tiled roofs, or wood shake roofs are designed like fish scales, overlapping pieces designed to shed water.
Flat roofing is a different animal. With extremely low slopes (between 1/4" to 1/2" per foot if constructed properly), flat roofs do not readily shed water. These flat roofs are designed as a monolithic roof surface and need to be able to handle some limited time of standing water.
There are three main types of flat roof systems:
- Membrane or 'Single-Ply' Roofing (such as EPDM)
- Built-Up Roofing (BUR)
- Modified Bitumen Roofing
EPDM is the newest flat roof technology (+/- 55 years) and BUR is the oldest (+/- 120 years). Modified Bitumen is in between (+/- 60 years). This tutorial will review the pros and cons of each flat roofing material.Continue to 2 of 4 below.
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Pros and Cons of EPDM Single Ply Membrane Roofing
There are several types of rubber/polymer membrane roofs including PVC, Neoprene, EPDM and a few others. However, EPDM (Ethylene Propylene Diene Monomer) is the most commonly used, especially in residential applications.
EPDM roofing is made of recycled rubber materials, which makes it environmentally friendly. It also helps to insulate your roof and attic -- and cuts down on cooling and heating costs -- which makes it economically friendly as well. EPDM roofing shingles come in a wide variety of textures and colors.
- EPDM roofing is waterproof.
- It allows you to encase your entire roof.
- Repairs are relatively simple and inexpensive; homeowners should be able to do some as DIY projects.
- Roofs last between 30 and 50 years and hold up against wind, water, and fire.
- The roof deck doesn’t need reinforcement because EPDM roofing is lightweight.
- Leaks are very rare with EPDM roofing.
- EPDM roofing is durable -- it doesn’t scratch or scuff very easily -- and repairs are easy.
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- You must have an EPDM roof installed by a professional contractor who knows how to properly install the roof. It can be somewhat costly.
- Any exterior pieces -- pipes, HVAC systems, chimneys -- can pose a risk to your EPDM roofing and cause leaks if not properly flashed.
- Rubber roofing can be damaged by branches, foot traffic during installation, or storm damage. You just need to take more care when walking on a membrane roof.
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Pros and Cons of Built-Up Roofing (BUR)
Built-up roofing (BUR) was the most common type of flat roof type until single-ply roofing and modified Bitumen was invented. BUR uses tar and gravel to create a watertight layer over the roof. Some of the main benefits of built-up roofing include its longevity, its thick coverage of the roof deck, and its high resistance to damage. It’s an expensive roofing choice for a residential home, and some of the odors that come with tar and gravel can be disconcerting. Here are some additional pros and cons of built-up roofing:
- Built-up roofing can last for 10 to 15 years with regular maintenance and repair.
- Several types of built-up roofing exist to meet your needs -- smooth asphalt built-up, ballasted asphalt built-up, cold built-up, etc.
- It offers great protection against water, UV rays, and inclement weather.
- It is low maintenance and costs very little to maintain throughout its lifetime.
- It’s easy to remove layers when repairing or resurfacing the roof.
- The gravel in built-up roofing makes it highly resistant to normal foot traffic.
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- Its installation takes a long time because making it involves a number of materials -- asphalt, coal, tar, gravel, etc.
- Potentially hazardous fumes and vapors are emitted during installation.
- It has high initial installation costs.
- It is susceptible to wind and high levels of moisture damage.
- It’s incredibly heavy and requires that roof joists are strengthened before it’s installed.
- It’s sometimes hard to find the source of a leak and sometimes requires dismantling the whole roof.
- Built-up roofing is not flexible in cold temperatures and is susceptible to damage.
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Pros and Cons of Modified Bitumen Roofing
It did not take long for people to dislike the mess, heat, and smell of installing built-up roofs (BUR). But for 60 years a BUR was your only option. Then in the early 1960's a new technology came out called modified bitumen roofing (MBR). This type of roof leveraged the proven performance of BUR but also added roof wear layers or cap sheets that were polymer reinforced for strength and durability.
- Factory applied mineral surfacing for consistent application.
- Applied in overlapping rolls creating large seamless areas.
- Less complex to install than BUR saving labor and reducing installation error.
- Polymer reinforced roof wear layer provides better elasticity and flexibility at low temperature.
- A variety of application methods including hot applied, torch applied, cold applied, self-adhered.
- Low maintenance and durable.
- Low cost.
- Recyclable at end of useful life.
- Provides better durability than a BUR with similar ease of installation like EPDM.
- Some application techniques require an open flame/torch which requires special safety considerations.
- Overlapping joints must be correctly adhered to prevent a possible leak.