Protected Membrane Assembly
In a Protected Membrane Roof Assembly (PMR), the RS Base membrane and RS Separation Sheet are applied directly to the structural deck. The insulation, filter fabric and ballast are then installed over top of the membrane. This type of assembly “protects” the membrane from mechanical damage, UV rays and thermal icing. In the unlikely event that the membrane has been damaged to the point where a leaks occurs, it is easy to isolate and repair since the membrane does not allow the lateral water movement between itself and the substrate. This type of assembly is used in both new construction and retrofit applications. With three of the main causes of roof failures eliminated, this type of system ensures problem-free performance for years to come. PMR’s have the lowest life cycle cost of any mainstream complete system on the market today. Systems IWS installed in almost 40 years ago are still performing well today!
Gravel Ballast holds the insulation down and keeps it from being blown off in heavy winds. IWS uses a large diameter, course graded of gravel which minimizes the effect of the wind on the dispersion of the ballast. In other words, it stays where we put it. Corners do not have the gravel “swept” off in high winds creating a potentially dangerous situation. Course gravel is much harder to spread than round shaped gravel or smaller diameter gravel, but the end result is much better. Damage to the membrane system through course gravel is not a concern when installed properly. Ballast can also consist of finishing systems described in the Waterproofing Systems in place of gravel.
Ballast Reducing Scrim
Ballast Reducing Scrim is a woven geotextile fabric designed to form a large blanket over the insulation. This allows less gravel ballast to be used to hold down the insulation to float after a heavy rain without having the boards popping out of place and creating a dangerous situation on the roof. PMR assemblies are designed to hold a certain amount of water immediately after a heavy rainfall. As the water level rises the insulation will float. The weight of the gravel ballast helps displace the water and forces it to drain at a more controllable rate.
The insulation used in all Roofsaver Protected Membrane Assemblies is Dow Roofmate. It is Type 4 Extruded Polystyrene board which comes in a variety of R-values. The edges are ship-lapped to minimize gaps between boards while remaining fast and easy to install. The boards are dimensionally stable and when installed properly will maintain their R-value for the life of the assembly.
RS Separation Sheet
RS Separation Course is an SBS rubberized asphalt membrane designed to adhere to the top surface of the RS Base. It provides a non-stick surface over the hot rubberized asphalt on which to place the insulation. This allows the insulation to move independent of the RS Base and ensures the positive properties of each are not working against each other in the assembly.
RS Base Hot Rubberized Asphalt is a monolithic, self-healing and liquid applied membrane. The membrane is heated at ground level in a specially designed melting kettle and applied to the substrate using a squeegee like applicator. This ensures there are no voids in the membrane system. It is applied in two monolithic costs separated by RS Reinforcing Fabric. Applying the system in this manner provides two truly monolithic layers of protection at all projections and flashing details.
RS Reinforcing Fabric
RS Reinforcing Fabric is spun-bond polyester scrim sheet designed for use with Hot Rubberized Asphalt Systems.
Primer is an asphalt cutback designed to penetrate the surface of the concrete deck and seal in any dust remaining on the deck after cleaning it. This helps maximize the already tenacious bond of RS Base to the concrete deck.
Structural Concrete Decks must be clean, dry and free of frost. New concrete must be sufficiently cured. Cure time can vary considerably depending on temperature, humidity and thickness of the pour. RS Base can be applied to decks cured less than 28 days providing moisture content is below acceptable limits. New concrete should have a wood float finish to maximize adhesion of the membrane.