What Are the Flat Roofs Systems and Why are They so Popular

Although flat roofs are in constant demand in residential and commercial construction, they are not as practical as sloped roofs.

A flat roof allows water and snow to settle what is a great inconvenience and can cause leaks over time, due to breakage of the seams.

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And then, we wonder why these types of roofs are so popular and sought after, when from engineering standpoint are inferior to sloped roofs.

There are two main reasons why these flat roofs are so popular.

1. Flat roofs are not as expensive as sloped roofs. In fact, they are the most cost effective type of roof.
2. They have a modern and contemporary look reflecting through their lines the horizontal lines of the surrounding landscape.

However, we meet these horizontal lines not only to the new housing construction but also in many traditional houses or commercial buildings. It is a feature of Western architecture and many old buildings have horizontal structural elements such as flat roofs above porches, garages, shed dormers or balconies. These horizontal straight lines are more common in urban than rural area.

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Flat Roof Systems

1. Metal Roofing

Metal roofing is the most common roof type due to the following factors:

– It is a energy efficient roof reflecting the heat;
– It requires low maintenance;
– It has a long life span;
– It is resistant to fire;
– It is waterproof;
– It is safe and durable.

We can find different types of metal roofs that can include corrugated (ribbed) panels and roofs made of aluminum.

Truly, flat roofs are the best choice for roof construction. However, they have a major disadvantage. They are expensive but in essence they worth their price. They are extremely durable, long lasting and they requires practically no maintenance.

2. Built-Up Roofs (B.U.R.) / Tar and Gravel/ Torch Down

This kind of flat roof is formed from several (three or more) layers of waterproof materials. Each of these ply of materials is soaked in tar and is applied with a hot-mopped or with a torch. In top comes a layer of gravel or tiny river stones.

Lately, there were major advances in roofing technology. We can find today, new technologies and modern materials with much higher qualities than this classic asphalt B.U.R.

However, B.U.R. still stand on the roofing construction market because is one of the cheapest flat roof systems. All materials part of this roof system are low cost, but the process of installation is quite messy.

The materials that can be included in B.U.R. are the following:

–  A layer of Bitumen Saturated Felt
– A layer of Coated Felt
– A layer of Polyester Felt or other kind of material
– A surfacing made of gravel, emulsion, asphalt or granule-surfaced sheet.

I can say that Build-Up Roof is the oldest system of flat roofs. At the same time we have to recognize the main quality of this system. It is a reliable roofing system. In fact, it is the perfect way of installing a new flat roof.

Generally, this roofing system consists of three parts such as:

1. Waterproofing Component;
2. Reinforcing Component;
3. Surfacing Component.

3. Modified Bitumen

Modified bitumen is a flat roof system that is applied with a torch as B.U.R. What sets it apart from B.U.R. are the materials that compose it, such as elastomers and rubber. These materials make it more flexible and stronger than B.U.R. They have modifiers added namely:

– SBS ( Styrene Butadiene Styrene)
– APP (Atactic Polpropylene)

SBS and APP give this roofing system the qualities of rubber, strength and flexibility.

A Modified Bitumen roll can cover between 100 and 112 sq feet.

The top surface of Modified Bitumen is a smooth surface and it has included gravel, slag, mineral granules, aluminum or copper that it is set in the hot asphalt.

Usually modified bitumen is applied in two or three ply system according to the type of substrate. Often this system is applied in conjunction with Built-Up roof materials. This creates a great roofing system very popular in industrial, commercial and residential applications.

←4. Asphalt Roll Roofing

Asphalt Roll system consists:

  • – Plies of roof felt and cold asphalt cement
  • – An asphalt-saturated felt layer(or fiberglass felt layer)
  • –  Mineral and granular layer

The main advantage of this roofing system is the inexpensive and easy installation. However, it is not really, a suitable flat roofing system.

Asphalt Roll Roofing system is fit more for slightly sloped roofs than flat roofs. Also, they have a short life span (10 years) and they require a continuous maintenance.

You should inspect periodically the roof. It may be affected by the vicissitudes of weather such as ice, snow, water pounding and ultraviolet light.

However, it is a very inexpensive option and could be installed even, by an amateur.

5. Polyvinyl Chloride (PVC) Roofing

This flat roofing system is also, known as Vinyl Roofing.

PVC roofing consists of thermoplastic membrane between two plies. This type of roofing system has 25 years life expectancy.

It is used for decades in North America and Europe and it is ENERGY STAR rated. A PVC roofing system can decrease your home cooling bills.

In addition, this kind of flat roof is extremely resistant to chemicals such as greases, acids or oils.

It is very popular in warehouses, markets or other commercial applications.

6. Rubber Membrane:

In fact, the technical name of this roof is EPDM (ethylene propylene diene monomer) and it looks like a tube. Rubber Membrane is well known for:

– Durability and Strength
– Thermal Insulation
– Easy Installation
– Easy Reparation of any leaks

However, rubber membrane has two main disadvantages. It is vulnerable to accidental punctures and it is an expensive type of flat roof.

The EPDM rubber membrane is relatively a new system in the roof construction. It requires an easy installation and any handy homeowner can install this kind of flat roof.