Top Commercial Flat Roofing Types: Pros and Cons

Commercial Flat Roofing

Are you looking for an answer as to what flat roofing to choose for your commercial buildings? Well for your information there are many types based on the shapes and materials used in roofing. One popular roofing type in commercial buildings is flat roofing. The reason due to which flat roofing is widely chosen for commercial purposes is because it is comparatively more cost effective and makes a better choice in terms of affordability.

If you are in the process of making a decision as to what type of flat roofing to go for your building, we suggest you do enough research about what flat roofing option suits better for your building, keeping in mind that flat roofings are available in various materials.

In this blog we will try to cover maximum information regarding flat roofing, their types, the materials used in flat roofings, and most importantly their pros and cons with cost estimation.

What is flat roofing?

As the name says, when a building’s roof is termed flat, it means the roof has a minimum slope, let’s say lower than 10 degrees, and is called Flat Roofing. This roofing type is obviously different in shape than sloped roofing, as flat roof does not have a steep slope and is comparatively an uncommon choice in residential housings. Although it can be used in housings too, it is more popular in industrial and commercial building roofings.

Flat roofings have different types based on certain material usage for their making; and most widely used materials in flat roofing include EPDM, TPO, and PVC; these materials are chosen based on their longevity and durability.

Types of Flat Roofing Materials

The typology of commercial flat roofing is categorised on two basis:

  • Positioning of the insulation layer 
  • Type of the materials used

Positioning of the insulation layer

When it comes to classifying flat roofing types, based on insulation layers, there are mainly four types, namely; warm roof, cold roof, inverted roof and compact roof.

Though there always can be further divisions in these types, knowing the main types will help you get an overall idea as to what better suits your housing need.

Warm roof

A cold roof is a roof structure in which there is a cavity ventilated with outside air between the roof floor and the insulation. This build-up can cause significant damage due to internal condensation and the rotting of any wooden roof decking.

Therefore, this type of roof is not recommended for newly constructed buildings but rather to be utilised during renovation projects, where there is a need to convert older or worn out roofing into warm roofing.

Inverted Roof

An inverted roof is a special type of flat roof where the insulation is loosely laid on top of the waterproofing. Specific types of insulation have to be used in this roof type. To prevent internal condensation, it is recommended to increase the insulation thickness by at least 20%.

This means using at least 45 mm of dry insulation material and a drainage layer with a small air cavity. The BDA (Building Designers Association) recommends against applying a green roof finish to an inverted roof due to the risk of internal condensation.

Compact Roof

A compact roof is a type of warm-roof construction that utilizes a two-layer bitumen membrane. Unlike traditional warm-roof construction, all layers in a compact roof are homogeneously connected, including the substrate, which eliminates the risk of water flooding.

Another type of compact roof that emerged in the early 21st century is a wooden structure completely filled with insulation material. This roof structure is similar to a cold roof because it lacks a layer of air, which can lead to well-known problems. The technical regulations for constructing such flat roofs highlight the numerous risks involved.

Designing and implementing this type of roof structure requires specific expertise, approach, and experience. Therefore, it is generally not recommended to use the wooden compact roof (timber structure).

Flat roofing types based on materials

The categorization of flat roofing based on materials involves some technical knowledge as many roofing-industry jargons have to be used even in the simplified version.

We have tried to make the material based types simplified to ensure better understanding for the reader.

Built-up Roofing (BUR)

Built Up Roofing (BUR)

The constructors know that in the roofing world Built-up Roofing (BUR) is a traditional roofing system which has a different construction mechanism because it is made of multiple layers of fiberglass.

These layers are further coated with tar or asphalt. The tar or asphalt coating creates a waterproof barrier, hence making Built-up Roofing (BUR) weather and heat resistant.

Modified Bitumen

This flat roofing type is made of asphalt-based roofing material that is reliable against any sort of punctures and highly durable against tears, thus adding to its longevity and durability. 

The warranty in terms of longevity and durability is because the asphalt-based roofing material is further strengthened by adding a polyester layer or fiberglass mat.

PVC (Polyvinyl Chloride)

PVC (Polyvinyl Chloride)

This flat roofing material is made of thermoplastic, which is a reliable name in roofing material because of its highly durable and with the strength to not only resist chemicals, and fireproof (to a great extent).

PVC also stands safe against extreme temperatures, it is energy efficient and UV resistant.

EPDM (Ethylene Propylene Diene Monomer)

This is a FLAT roofing material type which is trusted for its durability, longevity, especially flexibility because EPDM is a synthetic rubber membrane; which is resistant to Ultraviolet (UV) rays, ozone layer, this it can tolerate harsh temperatures, this qualifying it as an option for flat roofing.

TPO (Thermoplastic Olefin)

A FLAT roofing material type which consists of basically a single or one layered roofing ply. This one layered roofing ply is manufactured by thermoplastic polyolefin.

This flat roofing material is famous among building constructors for it has the mechanish to reflect Ultraviolet (UV) rays and is an efficient energy saving FLAT roofing material type.

Advantages and Disadvantages of Flat Roofing

Like any other roofing type, flat roofing has benefits as well as drawbacks. To receive maximum longevity and durability out of your choice for flat roofing, it’s advisable you know your housing and area requirements based on weathering conditions and usage.

Advantages of Flat Roofing

Flat roofing is a top choice for roofing in commercial buildings, because there many advantages of flat roofing like its energy efficient, cost effective, provide extra space for rooftop designs and more.

Lets know more about these advantages:

Energy Efficient

Flat roofings are considered more energy efficient as compared to other roofing types because the construction materials used in flat roofing types are EPDM, BUR, TPO andPVC. These materials have great reflective properties.

They have the design material and mechanism that have strength to reduce the quantity of heat absorption by the building, keeps the inside of the building cool and saves cooling cost to the residents and building owners.


It’s a common choice by building constructors to opt for flat roofing, when it comes to installation of roofs in commercial buildings because flat roofs are normally less expensive to install, and their maintenance cost is also more affordable as compared to other roofing types like sloped roofs and others.

The reduction in price is due to the fact that during the construction process, flat roofing requires less materials usage and shorter construction time.


When it comes to any defect in the roofing, the defect can easily be spotted and accessed in flat roofing. Resultantly, you can get the maintenance and repair services timely and with ease.

As a building owner or the resident flat roofing choice save your maintenance and repair cost and time over years.


One end product that is the side benefit of choosing flat roofing is that the commercial or the residential building that has flat roofing will have a rooftop which can be converted to a garden or any additional outdoor space of your need based choice like a terrace or rooftop attic.

Disadvantages of Flat Roofing

When we talk about the disadvantages here, these are not embedded in the built-up in the roof-type rather arise with improper installation or in cases where drainage and weather conditions are not considered ahead of the roof installation.

These problems can normally be avoided when repair and inspection is done timely; however we are not saying that flat or any roofing type is immune to defects.


Flat roofs can have drainage issues if drainage mechanisms are not properly designed and maintained it can damage the roof. So if the drainage mechanism in your building is not resistant against water ponding, or leaks, then the roofing can be damaged internally, thus reducing the longevity of the roofing.

Weather Damage

As compared to other roofing types, flat roofings are more likely to get damaged from rainfall or snow storms or even extreme windy weathers. This is because they have thin insulation layers, which are not very strongly resistant to rough weather in long term harsh weathering.

That is not suitable for all climate types, especially areas that have heavy snow or frequent rains, because this creates water ponding, which in absence of proper draining mechanism can reduce roof’s durability and lifespan.

Concluding Statement

As a commercial building owner or constructor your option for flat roofing should be for the fact that you want to make a viable option for your building so that the roofing has a long life span and greater durability.

This is achievable and possible if your building’s flat roofing is installed with customised design so that it is according to the weathering conditions of the area, and you are following the standard protocols of roof installation and maintenance protocols.

Now you can expect the results to yield warranty, and be financially prudent. Lastly, we always recommend consulting with a professional roofing contractor to determine if opting a flat roof is the right choice for your specific building according to your location.



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