Protected Membrane System

Unlike in a traditional roofing system where the membrane is attached to the substrate by adhesive or plates and screws, in a roofing system you are able to loosely lay the Sarnafil G 476 membrane down without any attachment due to the fact that the membrane is the bottom layer in the system and will have things like pavers or soil on top to keep it down.  The Sarnafil G 476’s seams are also hot-air welded for maximum water tightness.

Below are some of the reasons why a loose-laid roofing system might be the best fit for your project.

When your project demands absolute system integrity with maximum watertight security, Sika Sarnafil’s self-adhered roofing system is for you. The system consists of the robust G 476 Self-Adhered (SA) membrane, a composite sheet comprised of Sarnafil G 476 roofing membrane with a closed-cell foam backing. The foam backing is factory-coated with a pressure sensitive adhesive and is perfect for new construction over concrete decks.  It can also be used effectively on renovation projects where the old roofing system can be removed completely, or where a new concrete topping slab is placed over the structural deck.

Sarnafil G 476 SA also doesn’t require hot asphalt kettles or flammable adhesives like other adhered roofing systems. This improves worker and job site safety and is much better for the environment.

Below are some of the reasons why a self-adhered roofing system might be the best fit for your project.

When your building demands absolute system integrity with maximum watertight security, Sika Sarnafil’s self-adhered roofing system is for you.  The system uses the robust Sarnafil G 476 Self-Adhered (SA) membrane – a composite sheet comprised of the heat-weldable G 476 roofing membrane with a closed-cell foam backing.  The foam backing is factory-coated with a pressure sensitive adhesive and is protected by a plastic release liner which is removed during installation.

Sarnafil G 476 SA combines the time-tested, proven performance of Sarnafil G 476 roofing membrane with the added security of an adhered sheet system. G 476 SA provides peace of mind for specifiers and owners who value the benefits of an adhered system and thermoplastic technology.

The flexible foam backing layer conforms to minor irregularities in the substrate and provides a cushion for the G476 roofing membrane. The pressure sensitive adhesive provides a tenacious bond to the substrate mitigating potential water migration under the membrane. The integration of G 476 membrane with a foam backing layer and pressure sensitive adhesive eliminates the need for a field installed separation layer and adhesives. This ‘all-in-one’ product increases applicator productivity and helps keep the project on schedule. Sarnafil G 476 SA also doesn’t require hot asphalt kettles or flammable adhesives, improving worker and job site safety.

Sarnafil G 476 SA is best suited for new construction. It can also be used on certain renovation projects where the old roofing system can be removed, or where a new concrete topping slab is placed over the structural deck.

Advantages:

• Robust, factory-manufactured composite sheet
• Conforms to minor surface irregularities and mitigates water migration under the sheet
• Improved applicator productivity and job site safety
  

The most common design approach over a metal deck is to build a ‘conventional’ loose-laid roof assembly under the vegetated cover. 

The rigid insulation material is typically extruded polystyrene (XPS), which is resistant to moisture absorption and has been used in green roof applications for decades. It is available in 40 psi, 60 psi, and 100 psi compressive strengths so it will not crush during construction or under load after placement of the vegetated cover.

Local building codes usually require the installation of a rigid, fire-tested thermal barrier over the metal deck prior to installing the XPS insulation board. A separation felt is installed over the XPS prior to installing the roofing membrane. 

Rigid isocyanurate foam insulation may be used in this configuration. The benefit is it does not require a thermal barrier. However, since isocyanurate foam is typically manufactured with a 20 or 25 psi compressive strength, rigid hardboard should be installed over the isocyanurate insulation to protect it from damage and potential long-term creep from the weight of the vegetated cover. The Sarnafil G 476 roofing membrane is installed over the hardboard.

Both XPS and isocyanurate insulation are available in tapered designs to enhance drainage.

After the Sarnafil G 476 is installed, it is covered by a drainage composite followed by the vegetated cover.

Advantages:

• Insulation is protected from the elements
• Insulation will not float since it is under the roofing membrane
• Allows the designer to create slope in the roof assembly