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The 4 Main Ingredients in a Flat Roofing System

Flat Roofing

Flat roofing is more common on commercial buildings than houses for several reasons. For example, a flat roof expands commercial square footage to enable meeting space or gardens. They also provide space for HVAC and other commercial equipment needs. These benefits come at a lower cost than that of sloped rooftops.

When considering a flat roofing system for your commercial or residential property, it is important to know about your material options and the roofing system needs. As explains, there are six key types of roofing materials for flat roofs and four primary components.

Six Roofing Materials to Choose From

For your flat roof system, the six key materials you can choose from include:

  • Ethylene Propylene Diene Monomer (EPDM)
  • Thermoplastic Polyolefin (TPO)
  • Spray Polyurethane Foam (SPF)
  • Modified Bitumen
  • Green Roof System
  • Built-Up Roof (BUR)

Ethylene Propylene Diene Monomer (EPDM)

EPDM is a rubber roofing material widely used because of its low cost and strength. It also weighs less than other flat roof systems, reducing reinforcement requirements for the roof decking. There are also multiple ways to install EPDM, whether by using adhesives, stone ballasts or fasteners.

Thermoplastic Polyolefin (TPO)

TPO membranes are like a hybrid of EPDM and PVC. This system's primary ingredient is rubber. But it also uses fillers that add strength, such as talc or fiberglass. TPO is more affordable than rubber EPDM and the material is energy efficient.

Spray Polyurethane Foam (SPF)

SPF roofing is a sprayed foam application onto an existing flat roof. The material expands before hardening and provides great energy savings, keeping the building interior warmer in winter and cooler in summer. The expanding material also seals small holes while increasing roof strength, preventing moisture penetration and blocking pest entry.

Modified Bitumen

Modified bitumen is also called roll roofing. It features a smooth or granulated surface. Its light color keeps the sun's rays out and reduces your cooling costs. The material is also low maintenance and recyclable.

Green Roofing

Green roofing for a flat roof is essentially a rooftop garden. These systems provide environmentally advantageous options for use with energy conserving benefits. Shade plants cool the roof's surface and keep interior temperatures lower during summer heat. It also increases the appeal and marketability of your building. However, rooftop gardens weigh more than other types of flat roof systems and often require roof reinforcement prior to installation.

Built-Up Roof (BUR)

BUR roof systems have been around for over a century. These include layers of fabrics and bitumen applied by a skilled contractor. Benefits include durability, with these roofing systems lasting up to 15 years. They also protect the roof from damaging UV rays and inclement weather effects.

Flat Roofing

Four Main Ingredients in a Flat Roof System

There are four main ingredients to any flat roof system, such as those made with the above materials. These include:

Plasterboard Ceiling

The visible portion of your flat roof system is the plasterboard ceiling. This covers the whole roof and blocks visibility of other materials, including the decking and insulation. To keep moisture build-up from occurring because of condensation, this surface features vents.


Decking is the framework of your flat roof. It consists of wood beams use to provide structure and form. Above the skeletal form is a timber deck of plywood, which supports your roofing contractor for repairs and structural inspections.

Insulation and Vapor Barrier

Together, the insulation and vapor barrier keep heat and moisture from damaging your decking. The insulation absorbs the sun's heat and rays to block its effects. The vapor barrier prevents buildup of moisture and leaks.

Waterproofing and Covering

The waterproofing material for your flat roof is a sheet or fabric applied to its surface. This layer keeps weather-induced leaks from penetrating other layers. The protective covering also keeps weather effects at bay, sometimes with special coatings applied for greater resistance.

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