Adhere or Attach? Which is better?

Roofing on commercial properties is typically applied in one of two ways — by adhering it or mechanically attaching it. Is one way better than the other? The debate continues as manufacturers go back and forth claiming their way is better.

To put it simply, there really is no “best” roofing system. A variety of roof options will do the job provided it is appropriate for the building, climate and is installed correctly.

Our suggestion is to review all the advantages and disadvantages and see what is right for your property. It is also a good idea to consult a professional roofing company to help you make a final decision. They’ll know the codes for your area, as well as what has worked well for other buildings in your region of the country.

Adhere

When roofing material is adhered, it is glued down to insulation boards below it. The insulation boards serve a dual role of providing insulation and securing the roof using screws. Then the final layer of glue and roofing material is added on top to create a waterproof seal.

Advantages

• The single-ply membrane is attached to the topmost surface of the roofing assembly through the use of adhesives, without penetrating the membrane. This method secures the membrane across the entire roofing assembly.
• Provide better wind uplift rating with fewer seams.
• Prevents thermal bridging from screws to inside spaces.
• No mechanical fastener plates to be stressed under certain environmental conditions.
• Easier to service in the event of a leak.
• Prevent condensation which can lead to corrosion and rusting of deck and fastener.
• Often have more warranty options and lower cost of ownership.
• Adhered roofing systems lay flatter and are generally more visually pleasing.

Disadvantages

• More expensive to install.
• Longer installation time.
• Increased likelihood of fasteners hitting a conduit or light system that is close to the deck.
• Adhesives produce a very foul smell during installation.
• New Low-VOC requirements mean dramatic changes to bonding adhesive formulas, which may affect performance.
• Since the membrane is only glued to the paper face of the insulation, if the insulation face begins to peal up, or any wind gets under the system, fully adhered roofs can peal up and blow off.

Mechanically Attached

Nearly 80% of commercial roofs are mechanically attached. First a membrane is laid down, then screws are driven directly into the insulation boards into the metal deck below. The screws are strategically placed so that the next layer of membrane covers the edge of the next sheet and the screws. A watertight seal is created by heat-welding the membranes together.

Advantages

• Roofing rarely fails over time.
• There are no foul smells when installing.
• Ease of Factory Mutual (FM) compliance.
• Ability to improve wind ratings.
• Obtainable with single ply systems of any kind.
• Less expensive to install.
• Quicker to install.
• Can be done in colder weather.

Disadvantages

• More perforations means more chances for leaks.
• Penetration of fasteners can hit conduit systems in deck, like lighting systems.