New Commercial Roof? Some Less Obvious Factors to Keep in Mind – Part 1

The most important consideration for selecting a new commercial roofing system is choosing one that will provide good weather protection for your workers and contents. In this first of two articles, we discuss some aspects of a commercial roof selection you might not have thought of, that can help ensure a long-term watertight installation.

Membrane Width: Single-ply membranes are available in several widths, and manufacturer Duro-Last makes prefabricated sheets that can cover up to 2500 square feet of roof surface. If your roof has lots of open space without many penetrations or curbs to work around, you should consider a wider membrane for those areas. They require less rooftop seaming, which speeds the installation and, more importantly, reduces the possibility of contractor welding errors and subsequent leaks.

Attachment: There are multiple attachment methods that are used for single-ply membranes, and the best one typically depends on the surface underneath.

  • Mechanical attachment uses screws and plates that go through a fastening tab that gets covered by a section of membrane to ensure watertight-ness. The screw penetrates the tab, insulation and underlying deck to keep the roof membrane securely in place. Mechanical attachment methods can be used on wood, lightweight concrete, cementitious wood fiber, gypsum, and structural metal roof decks. The contractor should make sure that the right fastener is used for the specific deck type.

commercial roof membrane fastening tab
A Royalty installer mechanically attaches a roof membrane sheet fastening tab to the deck underneath.

  • Adhered roofing systems are glued to underlying insulation or directly to the roof deck, and are especially appropriate for concrete decks. Some roofing membranes are fleece-backed, to help provide better a better adhesive bond between the membrane and the substrate underneath.
  • Induction welding is gaining popularity as an installation method for commercial roof systems. The membrane is attached to a specially-coated fastening plate that the contractor first fastens through insulation and/or roof cover boards to the roof deck before laying the membrane down. A special welding tool then heats the plate through the membrane, securely bonding the plate’s special coating and the bottom of the membrane together.

Roof Deck: Regardless of how the roofing membrane is applied, the integrity of what’s underneath it is critically important. An unsound deck – one that’s waterlogged, rusted or otherwise compromised – will not enable the membrane to be properly secured, and that will be a problem. The contractor installing the new roof system should replace any areas of the deck that have degraded to such a degree where fasteners will not stay in place or adhesive will not stick.

In addition to these factors, the long-term success of any roofing system depends on the installing contractor’s experience and attention to quality. We’ll have more to say about that in our next post.