What is a Fully Adhered Roof System?
Fully Adhered roof systems have been installed since the mid-1960s. They are known for being aesthetically pleasing and having the least amount of membrane fluttering since every square foot of membrane is bonded to the insulation. Manufacturers also give fully adhered roofs the highest wind ratings, whether it is a fully adhered TPO roof system or a fully adhered EPDM roof system. However, it is important to note that Factory Mutual gives higher wind ratings to mechanically fastened roof systems since it’s easier to add more fasteners to weak points in the roof system, such as the corners and perimeters.
Fully adhered roofing systems rely on rigid insulation to be fastened down thoroughly. As a result, fully adhered roof systems have fastening patterns of 12-24 fasteners per 4’ by 8’ rigid insulation board, far more than the 5-8 fasteners required for mechanically attached roof systems. The result is that fully adhered roof systems typically have more fasteners installed than mechanically attached roof systems!
Once the insulation has been thoroughly fastened down, the roofing membrane is rolled out. Then, the bonding adhesive (or glue) is applied to both the rigid insulation and the membrane. After, the membrane is placed on top of the rigid insulation, then rolled in for a tight bond. Where there are angle changes, for example around walls or rooftop units, the membrane is fastened and glued down to prevent the membrane from pulling, which causes numerous problems.
Similar to mechanically fastened roof systems, the rolls in a fully adhered roof system are bonded together based on the roof system type. For example, in a fully adhered EPDM roof system, after the first roll is glued down, the second roll of membrane is rolled out next to the first roll. Then, the perimeter of the second roll is cleaned, primed, and then covered by seam tape from the first EPDM membrane roll.
- A fully adhered TPO roof system, the membrane is cleaned and heat welded together.
- In a fully adhered TPO roof system, the membrane is cleaned and heat welded together.
Benefits of a Fully Adhered Roof
- Aesthetically pleasing.
- Proven system that has been installed for decades.
- No fluttering in the roof system.
- Offers the best manufacturers’ wind ratings.
- It can be a quiet installation when paired with OlyBond installation adhesives.
- Available with any single-ply roof system.
- Fully adhered roof systems are an excellent choice for roof systems that are in view of the public eye.
- They can also be a great choice for buildings where a high wind rating is necessary, although you can get the same or better ratings on a mechanically fastened system.
Drawbacks of a Fully Adhered Roof
- 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.
- Fully adhered is the most expensive installation method.
- Potential FM compliance issues with FM’s “Bubble test” where required.
- FM provides better wind ratings on mechanically fastened roof systems.
- 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.
