How is Commercial Flat Roofing Installation Done?

Commercial flat roofing is a straightforward process but one that requires roofing experts for installation. While it is a fairly simple process for professionals, you may expect variations from one project to another.

In this blog, we will take you through a commercial flat roofing installation process.

Key Stages of Commercial Flat Roofing

Installing a flat roof on a commercial estate requires some pre-preparation steps as well, so we will start from there:

Step 1: Pre-installation steps


The roofing expert will do a thorough inspection of the roof deck to understand its underlying structure. This is a crucial step for the roofing expert to identify whether the roof deck can support the weight of the new roofing system and if any repairs are required before carrying out the installation process.

Choosing Materials

After inspection, the roofing materials are chosen, be it modified bitumen or EPDM. Choosing the right materials will influence the commercial flat roofing installation process. Also, the budget, climate, and intended functionalities are taken into account during the pre-installation and material selection process.

Safety and Permit

At this stage, it is standard to obtain the necessary permits for starting and completing the roofing process. At the same time, proper safety measures have to be implemented for the workers and the surrounding area.

Step 2: Preparing the roof deck


The roofing experts clean the roof thoroughly, removing debris and ensuring a smooth and leveled surface for optimal membrane adhesion.

Installing the vapor barrier

The roofing expert then installs the vapor barrier to prevent moisture from entering the roof through the building’s interior and causing damage.

Step 3: Insulation

The roof is insulated to enhance energy efficiency by regulating the temperature within the building.

Some of the flat roof insulations include:

  • Phenolic foam roof insulation
  • Polyurethane Roof Insulation
  • Polyisocyanurate Roof Insulation
  • High-Density Extruded Polystyrene (XPS) Roof Insulation
  • High-Density Expanded Polystyrene (EPS) Roof Insulation
  • Glass Fiber Batts, Mineral Fiber Batts and Panels
  • Perlite Board

Step 4: Installing the waterproofing membrane

The waterproofing membrane is the core layer that ensures water tightness and is installed according to the manufacturer’s specifications. The membrane material may be rolled sheets of bitumen or EPDM, and the seams are sealed thoroughly to prevent leaks.

Step 5: Flashing installation

Flashing is installed around roof penetrations like the curbs, pipes, and vents. This installation is done to ensure a watertight seal at critical points.

Step 6: Installing a drainage system

Flat roofs offer more flexibility in terms of architectural design. However, they rely on proper drainage to ensure that water doesn’t pool and cause leaks. Therefore, a well-designed drainage system is crucial, which is why drains, scuppers, and internal slopes are incorporated to channel water away from the building.

Step 7: Additional layers

As mentioned, commercial flat roofing installation is a straightforward process but has a few variations from one building to another. So, depending on the roofing system chosen, a gravel ballast may be needed for added weight and protection. Also, a reflective top coating could be installed to improve energy efficiency.

Once the roofing installation is complete, a final inspection is done to ensure all elements are effectively installed and sealed. The roofing expert provides a preventative maintenance plan with scheduled regular roof inspections, cleaning drains, and addressing minor issues to optimize the lifespan of the roof.