Mechanically Fastened Vs. Fully Adhered Single-Ply Commercial Roofs: What's The Difference, And Which One Is Better?

Posted on: 21 January 2021

If your commercial building needs a new roof, you've probably heard about single-ply roofing systems. These roofs use rubber or plastic membrane panels to protect your roof from wind and water damage, and they're quite common in new commercial roof installations. They're durable, easy to install, and easy to repair, which makes them an overall excellent choice for a new commercial roof.

When installing a new single-ply roofing system, you'll have the choice between installing a mechanically fastened roof or a fully adhered roof. This refers to how the single-ply membranes are attached to your building during the installation process. To learn more about the differences between these installation methods and how to decide which one is the better choice for your building's new roof, read on.

Mechanically Fastened Roof Installation Process

When ordering single-ply membrane panels for a roof that will be fastened mechanically, the manufacturer creates them with holes along one edge of the panel. The work crew drives screws through these holes in order to secure the panel to the structural deck of your building. This process is repeated with each panel until they cover the entire roof of your building. Afterwards, the seams between each panel are welded together with a hot-air gun to create a single interconnected membrane that spans your whole roof.

Mechanically fastened roofs have the major advantage of being quick to install. Screwing the panels into the structural decking and welding them together can be accomplished rapidly by an experienced work crew, which means that installation costs are low.

The main downside of a mechanically fastened single-ply roof is that the panels are only connected to the structural decking by the fasteners. During high winds, air can make its way underneath the panels and push them upwards. This allows conditioned air from inside of your building to rise up outside, which can cause condensation to form on the underside of the panels if the temperature of your conditioned air is warmer than the temperature of the panels.

Condensation traps moisture underneath your roofing system, which can lead to your insulation boards becoming ruined. Once insulation boards become wet, their ability to protect your building from variations in outside temperature will be reduced permanently.

Fully Adhered Roof Installation Process

When installing a fully adhered roof, the membrane panels don't have any holes for fasteners on them. Instead, they're glued down to the insulation boards using an adhesive. Thicker insulation boards are used for a fully adhered roofing system than in a mechanical roofing system in order to provide added support, and they're screwed directly into the structural decking of your building.

A work crew will apply adhesive to the insulation board and the membrane panel, wait for it to cure slightly, and then roll the panel over the insulation board. Afterwards, the panel will be tight against the insulation board using a roller in order to provide a secure seal.

Fully adhered single-ply roofing systems take longer to install than mechanically fastened ones due to the fact that the work crew needs to wait for the adhesive to cure slightly before rolling out the membrane. This prevents the membrane from shifting too much against the insulation board while it cures further, providing a better seal. A longer installation time means that installation costs for fully adhered roofing systems are higher.

However, the fact that the roofing panels are fully secured to the insulation boards underneath prevents them from being lifted up by the wind. This prevents any conditioned air from leaking out of your building, which can help reduce your heating and cooling costs. It also eliminates the chance of condensation occurring, helping to protect your insulation boards from being destroyed by moisture.

Which One Is the Best Method for Your Building's Single-Ply Roofing System?

Overall, a fully adhered system is often the better choice for a commercial roof installation. Fully adhered systems protect your insulation boards from moisture, and damaged insulation boards are difficult and expensive to replace. When you need a new single-ply commercial roof installed, you should consider paying the extra installation costs for a fully adhered roof in order to better protect your building from condensation and water intrusion.