What are the most common types of flat roofs?

by | Dec 12, 2019 | Flat Roofing | 0 comments

The roofing market is divided into two main sectors, sloped vs flat roofs. Flat roofs are popular because they are cost-efficient, fast to install, and generally easier to maintain.

The flat roof sector is further subdivided into multiple types differentiated by the material used and related application process. Understanding the different types of flat roofs available will allow you to make an educated decision when selecting a roof for your structure.

This guide provides an overview of seven of the most common flat roof types.

7 Common Types of Flat Roofs

Here are some flat roof types commonly used by contractors.

1. Built-Up Roof (BUR)

Built-up roofs, BUR, are made of hot tar and gravel. The roof is usually made up of three or more waterproof ply sheets, with each sheet layered between a coating of tar. Gravel or stone is used to add ballast and enhance security.

BUR is one of the most affordable roofing materials available. It also earns high fire ratings since gravel is fire-retardant. One drawback of BUR roofs, however, is their bulk. The combination of tar and gravel can add a lot of weight to the underlying structure.

BUR roofing installation can also get messy if it’s not handled by an experienced professional.

2. Polyvinyl Chloride (PVC) Membrane

Polyvinyl Chloride (PVC) membrane is a single-layer roof installed in a single sheet, affixed using heat or a welded solvent. PVC is elastic and flexible, allowing for easy installation. It’s further lightweight and won’t add much burden to the underlying structure.

Another benefit of PVC membranes is that they are very flame resistant. Most PVC membranes can attain a Class-A fire rating. PVC can further withstand extreme temperature changes thanks to its elasticity and tends to hold up better under impact than BUR styles.

PVC thermoplastic is further UV-resistant and highly reflective. This can enhance the roof’s energy efficiency, as the structure doesn’t absorb the sun and get hot but instead reflects the ultraviolet rays.

3. Rubber Membrane

Rubber membrane roofing is also called ethylene propylene diene terpolymer, or EPDM for short. Rubber membrane roofs are lightweight and long-lasting and tend to be more durable than modified bitumen and BUR roof systems.

One con of rubber membranes is that they are quite dark in color. They thus absorb sunlight and heat and are less energy-efficient than lighter colored roofing materials.

4. Modified Bitumen

A modified bitumen roof consists of only one layer of adhesive roofing material. The material tends to be quite reflective, making for an energy-efficient roof that can help regulate building temperature and reduce heating and cooling costs.

Modified bitumen can be installed in two ways. Traditionally, a torch was used to adhere the material to the underlying structure. Without proper expertise, however, this installation method can pose a fire hazard. Modern modified bitumen roofs eliminate the need for a torch and rely on adhesive material.

One drawback of this roofing material is that it’s not as resistant to foot traffic and is thus less durable than other options like those described above.

5. Thermoplastic Polyolefin (TPO)

TPO is similar to PVC in some aspects. It’s made using ethyl propylene or polypropylene rubbers and affixed as a single, flat membrane. It can be adhered to the roof deck mechanically or using an adhesive.

The roofing material is white, making it light-reflective and thus energy-efficient. One significant advantage of TPO is that it’s bendable and elastic, so it can fit diverse roof shapes, even if they’re irregular.

6. Coating

A coating roof is made of resin-like elastic liquid. This is poured on and then allowed to dry. It offers excellent waterproofing and adequate protection against physical damage, impact, and wind. Coating roofs can range enormously in thickness, from 3 to 40 millimeters.

There are different types of coating available, including silicone and acrylic. In general, this is an affordable roof option. It’s also highly resistant to damage from the sun, mildew, and mold. Finally, roof coatings are very reflective, making them energy efficient.

7. Metal

Metal roofs are commonly made of steel or aluminum. Metal roofing is exceptionally long-lasting. This roofing material is also lightweight and easy to affix. You can even install it over existing roofing materials.

Metal is naturally a good conductor of heat. This makes metal roofing ideal in chillier climates. Note that metal roofs may not be viable for fully flat roofs, however. Usually, at least a slight slope is needed to ensure a secure installation.

The Final Word on Flat Roof Types

As you can see, you have many types of flat roofs to choose from, each with its own pros and cons. The best choice depends on your precise needs and preferences. For example, while some people prioritize price, others place a premium on durability or energy-efficiency.

If you aren’t sure what flat roof type best suits your needs, consult a contractor for advice.

Robert Johnson

Robert Johnson

Robert has over 40 years of experience in roofing industry and proud to share his experience and knowledge with local residents. He can be found blogging on Top Roofing Contractors site or actively building his roofing business in GTA.

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