Options For Flat Roofs

Correct Flat Roof Repair Installation

Roofing systems take abuse and have to be maintained. Pitched roofs are fundamentally built to shed water and keep snow from piling up.

As a result, sloped roofs that utilize asphalt shingles, tiles, or wood shakes are designed to work similar to fish scales – overlapping each other to shed the water and snow. 

Flat surfaces require different coverings and this article will discuss three options for flat roofs.

Flat roofing systems aren’t built that way. With extremely low slopes (between 1/4″ to 1/2″ per foot, if installed the right way), flat roofs don’t shed water easily. Flat roofs are good systems if done right. They do have some common issues that can be prevented if they are installed by a good roofing company.

Flat roofing systems are built as a monolithic roof surface and will have times where water is pooling and standing.  There are 3 main options for flat roofs including Built-Up Roofing (BUR), Modified Bitumen Roofing, and Membrane or ‘Single-Ply’ Roofing (such as EPDM).

EPDM is the latest flat roof technology (around 55 years) and BUR is the oldest (about 120 years). Modified Bitumen is between the others (+/- 60 years). Here are the pluses and minuses of each flat roofing system.

Built-Up Roofing Systems

Built-up roofing (BUR) was the most commonly installed type of flat roof until single-ply roofing and modified Bitumen came along.

BUR uses tar and gravel for a watertight layer on top of the roof. Some of its biggest benefits include longevity, the thick coverage of the roof deck, and high resistance to damage.

It’s a costly choice for a residential property, and some of the odors that come with tar and gravel can be bothersome. Here are some additional pluses and minuses of built-up roofing:

Pluses

• It can last ten to fifteen years with routine maintenance and repair.
• Several types exist — smooth asphalt built-up, ballasted asphalt built-up and cold built-up
• Great protection against rain, UV rays, and severe weather.
• Its low maintenance and costs little to maintain throughout its lifespan.
• You can remove layers when repairing or resurfacing the roof.
• The gravel in built-up roofing makes it resistant to normal foot traffic.

Minuses

• Installation is lengthy due to involving a number of materials — asphalt, coal, tar, gravel, etc.
• Potentially hazardous odors, fumes and vapors are emitted while being installed.
• It has high initial installation costs.
• It’s susceptible to high winds and unusually high levels of moisture.
• It’s heavy, which can require roof joists be strengthened before it’s installed.
• It can be difficult to find the source of a leak. At times, it requires dismantling the whole roof.
• It’s not flexible in colder climates and is prone to damage as a result.

Modified Bitumen Systems

It didn’t take long for the public to move away from the mess, heat, and odors of installing a BUR roof. But, for a long time, it was the only option. In the early 1960s, a new technology was developed – modified bitumen roofing (MBR).

It leveraged the proven performance of BUR and added roof wear layers or cap sheets that were polymer reinforced for strength and durability.

Pluses

• Factory applied mineral surfacing that makes the application consistent.
• Overlapping rolls create big, seamless areas.
• Easier to install than BUR which saves on labor costs and reduces installation mistakes.
• Polymer reinforced roof wear layer gives better elasticity and flexibility in colder temperatures.
• There are several application methods – hot applied, torch applied, cold applied, self-adhered.
• Its low in maintenance and durable.
• Its inexpensive compared to other systems.
• Recyclable materials at end of its lifespan.
• More durable than BUR with installation thats similar to EPDM.

Minuses

• Some application techniques require an open flame/torch which requires special safety considerations.
• Overlapping joints must be adhered correctly to prevent leaking.

Single Ply Membrane Systems

There are a few types of rubber/polymer membrane roofing systems – PVC, Neoprene, EPDM and several others. EPDM (Ethylene Propylene Diene Monomer) is used the most, especially for residential projects.

EPDM is constructed of recycled rubber materials, making it environmentally friendly. It helps to insulate your roof and attic.

In addition to covering your roof, it will bring down utility costs and make it economically viable as well. It comes in a large variety of textures and colors.

Pluses

• EPDM roofing is waterproof.
• You can encase your whole roof.
• Repairs are pretty simple and inexpensive; property owners can do some simple repairs themselves.
• They last 30 to 50 years and hold up against the elements and fire well.
• Its lightweight so the roof deck doesn’t need to be reinforced.
• Leaks are very rare.
• Its durable — it doesn’t scratch or scuff easily — and repairs are easily made.

Minuses

• Must be installed by a professional roofing contractor who knows how to properly install it. It can be somewhat expensive.
• Exterior features such as pipes, HVAC systems and chimneys, can pose a risk to your EPDM roofing and cause leaks if flashing is not properly installed around them.
• It can be damaged by branches, foot traffic or storm damage. You need to be more careful when walking on a membrane roof.

Remember to maintain your flat roofs, repair them if it needs repairs, and get them inspected every 5 years or so!