Single-ply roofing systems can be installed with either of two rather common methods: fastened mechanically to the roof deck or fully adhered with an adhesive.
Stress plates and screws are used to fasten the membrane in place. The system uses a roof membrane, mechanically attached to the roof surface, insulation, attached to the deck, and a vapor retarder.
The membrane is fastened to the roof deck by powerful adhesives. A vapor retarder is used along with insulation that is attached on to the deck mechanically. Adhesives then fasten the roof membrane to the insulation.
Pro and Cons Of Mechanically Fastened Vs. Fully Adhered Roofing Systems
There are several benefits and drawbacks of using our two flat roof replacement systems. Here are the common pros and cons you could experience:
Mechanically Fastened Pros:
- Rarely flops over time
- No foul smells when installing
- Ease of Factory Mutual (FM) compliance
- Ability to improve wind ratings
- Obtainable with single ply systems of any kind
- Penetration by the fasteners can hit conduit systems in the deck, e.g. light systems
Fully Adhered System Pros
- Tested and proven over time
- Aesthetically attractive
- Roof system does not flutter
- Provides desired manufacturer wind ratings
- An option with single ply systems of any kind
- Foul smell produced during installation
- This flat roof replacement method of installation is expensive
- Has issues with Factory Mutual (FM) compliance where the Bubble test is required
- Lacks good FM wind ratings
- There is a possibility of pealing of or blowing off of the roof in case wind gets access to under the system or when the insulation face peels up. This is because the membrane is only held tight on to the paper.
- The new Low-VOC necessities will require changes to be done on the bonding adhesives thus may hinder effective performance of the roofing system.
A professional roofing contractor is able to determine which method should be used in individual cases, after considering the roof product, building location, and the structure of the building. Each method has its own benefits – the question is which is right for your specific needs.
Jewett Roofing is a professional installer of flat roofing systems, serving St. Louis and the surrounding area.