Installing a roof on a commercial building is a complex process that requires careful planning and execution. From choosing the right materials to proper installation techniques, many factors come into play in ensuring the roof's longevity and performance.

With commercial roofs, installation can seem daunting if it’s something new for you. In general, when installing any building feature or add-on you must hire a team that knows what they’re doing. That said, in the process of installing a commercial roof, there are many questions left unanswered. 

This definitive guide will walk you through everything you need to know about commercial roof installation.

The Evolution of Commercial Roofing Materials

Over the last 50 years, membrane roofing has dominated the commercial roofing industry. Membrane roofs accounted for over 60% of low-slope commercial roofing in 2021.

Membrane roofs are easily the most popular commercial roof used. As to why that is, this has a lot to do with the fact that they are waterproof and prevent water intrusion in industrial or commercial buildings. Made predominantly from rubber, thermoplastic, and bitumen that’s modified, these are typically chosen based on your operational and business requirements.

Another reason membrane roofs are popular is the durability and versatility offered by materials like thermoplastic polyolefin (TPO), ethylene propylene diene monomer (EPDM), and polyvinyl chloride (PVC). These materials provide excellent weather resistance and long-term waterproofing.

Roof Attachment Methods 

Once the roofing membrane is selected, proper attachment is crucial. The roof can be attached using mechanical fasteners, full adhesion, or a combination of the two. Fully adhered roofs provide superior wind uplift resistance but can be more expensive.

That said if you want reasonable rates and roof installation that’s relevant to your weather conditions, hiring a local roofing company is helpful. For example, if you’re based in Vancouver and need your roof serviced, looking for roofing repair in Vancouver WA is the first place to start.

Mechanically fastened roofs are quicker to install but require regular maintenance of the fasteners. On the other hand, Ballasted roofs use stones or pavers to hold the membrane in place but have limitations based on the roof slope.

Historical Perspective on Roof Fasteners

Roof fasteners have evolved significantly over the past century. In a reroofing or Roof installation project, identifying existing fasteners provides insight into the roof assembly. For example, round head nails were prevalent in wood decking in the early 1900s. 

Crimped metal nails emerged in the 1930s. Drill tip screws became popular in the 1950s with the rise of steel decking. Understanding this evolution helps create an effective fastening strategy tailored to the unique needs of the roof.

Gypsum Decking: A World War II Solution

During World War II, gypsum decking became a popular roof base when steel was in short supply. Gypsum is inexpensive and fire-resistant but can deteriorate from moisture exposure.

When re-roofing a gypsum deck, checking for crumbling or missing sections is crucial. Targeted replacement or infill of damaged areas may be required before membrane installation.

Wood Decking: The 1940s Standard 

In the 1940s, heavy timber construction was the norm for roof decking or roof installation. Modern pressure-treated lumber helps wood stand up to the elements. But compared to today’s insulation standards, wood decking provides little thermal performance. 

Strategies like rigid insulation above the deck or thermal blocks between rafters improve energy efficiency. Wind uplift resistance can also be enhanced using threaded nails and hurricane ties.

Exploring Lightweight Insulating Concrete

For a truly resilient roof assembly, lightweight insulating concrete (LWIC) has advantages over traditional structural concrete. At 75 lbs/ft3 density, LWIC delivers an R-value of 2.1 per inch. 

This is double the insulation value of normal-weight concrete with less structural load. LWIC also achieves fire ratings over 4 hours, protecting the structure below. The roofing membrane can be applied directly to LWIC, eliminating the need for additional insulation layers.

Steel Roof Decks: Bridging the Flutes 

Corrugated steel decking gained popularity in the 1950s and became the dominant roof deck material. While the troughs—or flutes—provided structural capacity, they created discontinuities in the roofing assembly. 

Polyiso insulation boards designed to span the flutes helped remedy this issue. Screw fasteners 20mm (3/4”) longer than the insulation compensate for the fluted profile. This “bridging” technique provides secure membrane attachment.

Precautions for Using Long Fasteners

On roofs with multiple layers of insulation, longer fasteners become necessary. But screws over 6 inches can experience problems with pull-out resistance. Limiting insulation layers to no more than 4 inches mitigates this issue. 

Staggering the seams between layers also enhances holding capacity. Prior to reroofing, conducting pull testing helps verify the tensile strength of long fasteners into the deck. This protocol ensures the roof assembly withstands wind loads.

Here is an Expanded Section on Roof Attachment Methods:

Roof Attachment Methods

Once the roofing membrane is selected, proper attachment is crucial for performance and longevity. There are several methods available for attaching the roof components:

Fully Adhered Roofing 

This method bonds the membrane directly to the substrate using an adhesive. All seams are also sealed with adhesive. Fully adhered roofs provide maximum wind uplift resistance and are unlikely to blow off in storms. 

They also limit the billowing of the membrane. The drawback is that fully adhered application or roof installation is labor intensive and requires weather warm enough for the adhesives to bond properly.

Mechanically Attached Roofing

The membrane is secured to the deck using mechanical fasteners like screws and plates. Fasteners are also used at the seams between membrane sheets. Mechanically fastened roofs can be installed year-round and are faster to apply than fully adhered.

However, regular maintenance is required to ensure the fasteners remain securely in place. Loose fasteners can lead to membrane flutter and eventual failure.  

Ballasted Roofing

This method uses gravel, pavers, or other ballast to weigh down the membrane. The absence of fasteners or adhesives reduces labor costs but limits applications based on roof slopes. 

Ballasted roofs require parapets or edging to prevent ballast from migrating. Roof access for maintenance can damage the ballast surface over time. 

Roofing Cold Process

This method eliminates the use of adhesives or hot asphalt. Acrylic and silicone coatings are applied in a cold liquid state to adhere to the roof components. 

The cold process is considered more environmentally friendly but requires specific application conditions and skilled application.

Vacuum Membrane Attachment

This method uses heavy-duty plates with seals on the underside. A pump creates a partial vacuum between the plate and deck to hold the membrane in place.

 Vacuum attachment offers rapid installation and reliable uplift resistance. Limitations include additional equipment costs and difficulty accessing areas for maintenance.  

Self-Adhered Membranes

These modified bitumen, TPO, or PVC sheets have a factory-applied adhesive backing. They bond to the substrate when the release film is removed.

Self-adhered membranes provide quick installation and reliable performance, especially in flashing details. The adhesive backings can add cost compared to traditional membranes.

Conclusion

Choosing the optimal attachment method involves evaluating the existing roof, building usage, budget, and required performance. A qualified contractor can recommend the appropriate solution for your project.

With proper material selection, attachment strategy, and installation technique, a commercial roof can achieve decades of peak performance. Consult a qualified contractor like ABC Roofing for a customized solution backed by a comprehensive warranty. Contact us today to get started!

Guest Contributor: Daniel Martin