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What Roofing Material Is Best For A Flat Roof?

When it comes to flat roofs, choosing the right roofing material is crucial for ensuring the longevity and durability of your roof. In this blog post, we'll take a closer look at some of the most popular roofing materials for flat roofs, including modified bitumen, built-up roofs, spray polyurethane foam, and standing seam metal roofing. We'll discuss the pros and cons of each option, and provide some helpful tips for making an informed decision when it comes to selecting the best roofing material for your flat roof.

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EPDM Rubber

EPDM (short for ethylene propylene diene monomer) is a synthetic rubber membrane used for flat roofs, non-slip coating, among many other applications. It is a very durable material, resistant to weather conditions and can last over 20 years with proper care. 

The EPDM roofing membrane is available in both white and black. White tends to reflect sun rays away, meaning your building will be cooler with white EPDM than with a black EPDM roof. 

EPDM membrane is also available in a wide range of widths, from 7.5 feet to fifty feet. It generally comes in two thicknesses, 45 and 60 mils.

Installation

EPDM can be installed in various ways: 

  • Fully adhered: A strong adhesive is used to bond the EPDM membranes to the roof deck. 
  • Mechanically attached:  This involves pinning down the membranes using fasteners. 
  • Ballasted: A ballasted EPDM roof system involves laying down the EPDM membranes using river-washed stones, ballast or pavers – minimum of 10 pounds per soiree foot. Ballasted EPDM roofs are loose-laid, meaning the insulation and roof membrane are attached to one another or to the roof deck. 

Price

For an EPDM flat roof, you can expect to pay between $3.25 and $14.75 per square foot for the material and installation. Most times, the average cost will be between $4.50 and $5.50 per square foot.

Pros

  • Relatively easy installation – EPDM flat roofs don’t require special equipment or intensive labor. 
  • EPDM flat roofs are highly durable, lasting up to 25 years. 
  • Easy to repair.
  • Environmentally firefly – Most EPDM material is recycled and repurposed into new roofing. 

Cons

  • Vulnerable to tears and punctures. 
  • UV rays destroy the adhesives used on seams and flashing, leading to premature separation. 
  • EPDM roofing isn’t as eye-catching as say, TPO or PVC. 

TPO

TPO, is a single-ply plastic roofing membrane. TPO flat roofs are made up of a single layer of plastic and reinforced scrim TPO roofs are also called white roofs, due to their distinctive white and reflective upper surface. 

TPO membranes are generally available in two thicknesses, 0.045 inches and 0.06 inches. As opposed to EPDM, TPO requires more experienced roofing contractors, and more specialized equipment. 

TPO is made up of two sheets with a scrim in the middle. As time goes on, the chemical fillers and minerals in the top layer wash away. When this happens, your TPO roof may start leaking.

Installation

TPO membranes are installed either using adhesives or through mechanical fastening. Once the TPO membrane is laid out, the roof technician then returns with a hot air gun to weld the seams together.

Price

For a TPO flat roof, you can expect to pay between $3.50 to $14.00 per square foot for the material and installation. Most times, the average cost will be between $3.50 and $9.50 per square foot.

Pros

  • Heat welded TPO seams are less likely to come loose than glued together seams of other membranes.
  • TPO roofing has a white surface that reflects light, keeping the building below cool.

Cons

  • Hasn’t been on the roofing market as long as EPDM so improvements are still being made. 
  • TPO is prone to shrinking, making the roof rigid. 
  • TPO roofs are degraded by prolonged exposure to UV light.

PVC

PVC (polyvinyl chloride) roofing is a single-ply roofing membrane that’s been used on flat and low-slope roofs for over half a century.

A PVC roof consists of two layers. Polyester acts as reinforcement in between the PVC layers. 

PVC membranes are relatively thin compared to other flat roof materials. PVC roofing products come with thicknesses ranging from 40 mil (0.04 inches) to 90 mil (0.09 inches). Most common membrane thicknesses are 60, 80 or 90 mil.

Installation

There are 3 common ways to install PVC flat roofs. 

  • Fully Adhered PVC Roofing: In this case, the PVC membrane is attached to the roof deck using strong adhesive. This method is used when the building owners don’t want holes in their roof or if the roof deck material can’t grasp fasteners well enough.
  • Mechanically Attached PVC Roofing: This method involves securing the PVC membrane to the roof decks with the use of screws or other fasteners. It’s the best option for areas that experience extreme weather such as strong winds or tornadoes.
  • Induction Welded PVC Roofing: This process involves using electromagnetic induction to heat and seal the plastic. This method requires less fasteners and is less labor intensive than the other two installation methods. 

Price

For an PVC flat roof, the average is between $4.00 and $7.00 per square foot installed. However, it could go as high as $8.00 to $12.00 or more per square foot.

Pros

  • Heat welded PVC seams form air and watertight roofs which increase durability. 
  • Fire-resistant – PVC roofs are hard to ignite and burn slowly.
  • Chemical resistant.
  • Microbe resistant – Impermeability and water resistance of PVC make it an unsuitable environment for microbes and other organisms. 

Cons

  • Easy to crack in low temperature conditions. 
  • Can be hard to repair. 

Modified bitumen

Modified bitumen flat roofing is a type of flat roofing system that uses modified bitumen, a type of asphalt, as the waterproofing material. The bitumen is typically reinforced with polyester or fiberglass to create a stronger and more durable roofing surface. The modified bitumen is applied in multiple layers and can be heated with a torch or hot air gun to create a seamless and waterproof seal. This type of roofing is commonly used on commercial and industrial buildings.

Newer modified bitumen systems are peel-and-stick, which is safer than the torching down method.

Price

According to HomeAdvisor, the average cost to install a modified bitumen roof ranges from $3 to $7 per square foot. This means that for a 1,500 square foot roof, the cost would be between $4,500 and $10,500.

Pros

  • Newer Peel-and-stick membranes are easy to self-install.
  • Durability: Modified bitumen is a strong and durable material that can withstand extreme weather conditions and heavy foot traffic.
  • Easy to repair: Damaged areas can be easily repaired by heating the bitumen and applying it to the affected area.
  • Cost-effective: Modified bitumen is a cost-effective roofing option, especially when compared to other types of flat roofing systems.
  • Energy-efficient: Modified bitumen roofing can have reflective coatings to decrease the heat gain of the building and lower the air conditioning load.

Cons

  • The torch-down application method is considered a fire hazard.
  • Installation difficulty: Installing a modified bitumen roof can be difficult and requires specialized training and equipment.
  • Vulnerability to heat: Long exposure to high temperatures and UV rays can cause the material to dry out and become brittle over time.
  • Vulnerability to heavy foot traffic: The material is not suitable for areas with heavy foot traffic, which can cause it to crack and fail over time.
  • Vulnerability to poor installation.

Built-up roofs (BUR)

Built-up roofs (BUR) are a type of flat roofing system that is commonly used on commercial and industrial buildings. A built-up roof is constructed using multiple layers of materials, including felt or fiberglass, asphalt, and a gravel or mineral surface. The layers are applied one on top of the other, with each layer being heated and rolled to create a strong and waterproof seal.

Price

According to HomeAdvisor, the average cost to install a built-up roof ranges from $5 to $12 per square foot. This means that for a 1,500 square foot roof, the cost would be between $7,500 and $18,000.

Pros

  • Durability: Built-up roofs are strong and durable, able to withstand extreme weather conditions and heavy foot traffic.
  • Waterproofing: The multiple layers of materials create a waterproof seal that is effective in preventing leaks.
  • Flexibility: Built-up roofs can be applied to various types of roofing decks, making it a versatile option for different types of buildings.
  • Cost-effective: Built-up roofs are a cost-effective roofing option, especially when compared to other types of flat roofing systems.

Cons

  • Installation difficulty: Installing a built-up roof can be difficult and requires specialized training and equipment.
  • Heavy: Due to the multiple layers, Built-up roofs are quite heavy and require a strong structural support
  • Vulnerability to heat: Built-up roofs can be damaged by high temperatures and UV rays, which can cause the material to dry out and become brittle over time.
  • Gravel can clog gutters and scuppers.

Spray polyurethane foam

Spray polyurethane foam (SPF) is a type of insulation and roofing material that is sprayed onto a surface in liquid form and then expands to create a solid, seamless layer of insulation and waterproofing. The foam is made from a mixture of chemicals that react and expand when they are mixed together. This type of insulation and roofing material is commonly used on commercial and industrial buildings, as well as residential homes.

Price

According to HomeAdvisor, the average cost to install SPF ranges from $2 to $6 per square foot for roofing and $1.50 to $3 per square foot for insulation. This means that for a 1,500 square foot roof, the cost of the SPF roofing would be between $3,000 and $9,000, and for insulation would be between $2,250 and $4,500.

Pros

  • Easy to install: SPF can be easily installed by spraying it onto the surface.
  • Energy-efficient: SPF insulation can help to lower energy costs by reducing the amount of energy needed to heat and cool a building.
  • Seamless: SPF creates a seamless layer of insulation and waterproofing that is free from gaps or
  • Insulation: SPF provides excellent insulation, helping to keep buildings warm in the winter and cool in the summer.

Cons

  • Cost: The initial cost of SPF is relatively high, making it more expensive than other types of insulation and roofing materials.
  • Vulnerability to fire: SPF is flammable and can burn easily, which can be a concern in the event of a fire.
  • Health concerns: Spray polyurethane foam insulation requires special protective equipment and ventilation during the installation process, as the chemicals used in the spray can cause respiratory irritation and other health issues if inhaled.

Standing seam metal roof

Standing seam metal roof is a type of metal roofing system that is characterized by raised seams that run vertically along the roof. The panels used in this type of roofing system are typically made from aluminum, copper, or steel, and are secured to the roof deck using clips or fasteners. The seams between the panels are raised, creating a watertight barrier that prevents leaks.

Price

According to HomeAdvisor, the average cost to install a standing seam metal roof ranges from $8 to $20 per square foot. This means that for a 1,500 square foot roof, the cost would be between $12,000 and $30,000.

Pros

  • Durability: Metal roofing is a strong and durable material that can withstand extreme weather conditions and last for many years.
  • Waterproofing: The raised seams create a watertight barrier that is effective in preventing leaks.
  • Energy-efficient: Metal roofing reflects sunlight, which can help to lower energy costs by reducing the amount of heat absorbed by the building.
  • Low maintenance.

Cons

  • Noise: Standing seam metal roofing can be quite loud during rain or hail, which can be a problem for some buildings.
  • Expansion and contraction: Metal expands and contracts with temperature changes, which can cause it to warp or buckle over time.
  • Denting: Metal is prone to dents from hail storms and other impacts.

GRS Remodelling – Your Ideal Flat Roof Contractor

Now that you know the positives and drawbacks of the most common flat roofing systems, you can pick which material best suits your needs. Remember to consider your budget, climate of where you live, and availability of reliable contractors. 

At GRS Remodelling, we have the best roofing technicians ready to repair or bring your dream flat roof system to life. Learn more or contact us today and let’s start building your ideal flat roof.