Key Elements of Cold Applied APP Modified Bitumen Specifications

Cold Applied APP Polymer Modified Bitumen Membranes are often specified as two-ply membranes. These systems often consist of an APP Base Sheet and a Granule Surfaced APP Cap Sheet. Roofing with APP polymer modified bituminous materials is similar to built-up roofing in that the APP modified materials are used in redundant manners to effectively "build-up" a durable multiple-ply waterproof membrane. Generally APP modified bitumen sheet materials contain enough APP modified bitumen to provide for relatively low perm ratings, which makes them "membranes" in themselves. In other words, these APP modified bitumen sheets do not need interply layers of bitumen to provide the waterproofing component for the membrane. Cold applied modified bitumen adhesive is used to laminate the layers of the APP modified bitumen sheets together to form the roof membrane.

Cold Applied APP Polymer Modified Bitumen Membranes can be installed over insulated roof decks, uninsulated nailable decks and uninsulated non-nailable decks.

Roof Insulation

Although a wide variety of roof insulation such as perlite, wood fiber, and glass fiber insulation can be used underneath Cold Applied APP Polymer Modified Bitumen Membranes by far the most popular is isocyanurate with a latex or acrylic facer. Not only does isocyanurate provide a cost effective high R-value roof insulation but the latex or acrylic facer eliminates the need for a coverboard when a cold applied modified bitumen adhesive is used. When modified bitumen sheets are installed using "Hot Asphalt Bitumen" over isocyanurate roof insulation a coverboard must be installed over the isocyanurate board to prevent blistering problems in the modified bitumen membrane. The use of cold applied modified bitumen adhesive at normal roofing application temperatures eliminates vaporization of moisture on the isocyanurate board that often creates voids and blisters.

Suggested Performance Criteria for isocyanurate roof insulation:

• Isocyanurate roof insulation coplying with ASTM C-1289 Type II with latex or acrylic facer.

Attachment of Roof Insulation to the Roof Deck

Attachment of roof insulation to the roof deck is accomplished by either mechanical fasteners or adhesive attachment depending upon deck type.

Steel Roof Decks require single or base layer of roof insulation to be mechanically attached according to FMRC recommendations. Subsequent or additional layers of roof insulation to be adhered to the base layer of insulation with a solid mopping of hot Steep Type III asphalt or roof insulation adhesive. (Note: The insulation board thickness must be sufficient to span the flute opening without damage when subjected to normal roof construction traffic.)

Structural Concrete: The deck surface should be primed with an ASTM D-41 asphalt primer and allowed to dry. Roof insulation to be adhered to the primed concrete deck with a solid mopping of hot Steep Type III asphalt or roof insulation adhesive.

Wood Plank: The deck should be covered with a red rosin sheet and an ASTM D-4601 fiberglass or modified bitumen base sheet mechanically attached with annular shank fasteners with a minimum head diameter of 15/16". Roof insulation to be adhered to the base sheet with a solid mopping of hot Steep Type III asphalt or roof insulation adhesive.

Suggested Performance Criteria for Mechanical Fasteners or Insulation Adhesive:

• FM Approved Mechanical Fasteners
• FM Approved Insulation Adhesive
• Steep Type III Asphalt complying with ASTM D-312

Polymer Modified Roof Cement and Adhesives

Polymer modified adhesives are generally composed of asphalt that has been thinned, or "cut back", with solvent or mineral spirits, and blended with polymer modifiers and fillers. Polymer modified adhesives are typically produced in two grades: a low viscosity adhesive that may be spread in place using a squeegee or sprayed in place; or a flashing (trowel) grade which has higher viscosity properties and is more suited for application to vertical surfaces. The low viscosity polymer modified adhesives are typically used for adhesion of the APP modified membrane or APP modified base sheet to glass fiber base sheets, glass fiber felts and roof insulation surfaces. It is also used to bond plies of APP modified membranes and APP modified base sheets to form roof membrane assemblies. The flashing grade, or higher viscosity, adhesives are typically used to bond APP modified membrane flashings to vertical or steep slope substrates. In certain situations, polymer modified adhesives can be used to adhere roof insulations to substrates (i.e., base sheets, primed concrete roof decks, or base roof insulation layers).

There currently are no ASTM standards for polymer modified adhesives and mastics.

Suggested Performance Criteria:

• A thixotropic modified bitumen adhesive that is VOC compliant having a maximum VOC Emissions of 200 grams per liter.

APP Modified Bitumen Base Sheet

APP Polymer Modified Base Sheets are composed of a polyester or glass fiber mat that is saturated, impregnated or filled, and coated on both sides with APP polymer modified asphalt. APP modified base sheets serve several functions, principally:

• To separate the roof membrane from the substrate.
• To provide support for the membrane over slightly rough or irregular substrates.
• To serve as an attachment or base layer for the adhesion of rigid insulation board on nailable roof decks.
• To serve as a first layer in multiple ply APP modified roof membranes.
• To serve as a single layer temporary roof.
• To serve as a single layer vapor retarder.

There currently are no published ASTM standards for APP Polymer Modified Base Sheet.

Suggested Performance Criteria:

• APP Modified Base Sheet 80 mill thick.

APP Modified Bitumen Membranes

APP Polymer Modified Bitumen Membranes are manufactured as both smooth and granule surfaced membranes. The smooth surfaced sheets are regularly used interchangeably as base sheets and interply sheets in Cold Applied multi-ply APP modified bitumen roof assemblies. The granule surfaced membranes are used as both cap sheets and as flashing sheets in the Cold Applied modified bitumen systems.

APP modified bitumen membrane sheets are reinforced with a polyester scrim / mat or a polyester scrim / mat and a fiberglass mat. These fabrics are saturated, impregnated or filled, and coated on both sides with APP Polymer Modified Asphalt. The sheets are surfaced on one or both sides with very fine minerals, such as sand, mica, or talc, that serve as parting agents and prevent adhesion of the material while in roll form. Some sheets have plastic films that are intended to be burned off in the installation process.

WARNING! APP Modified Bitumen Membranes that have plastic film parting agents can NOT be used in Cold Applied Modified Bitumen Systems. The plastic film-parting agent prevents the modified bitumen adhesive from coming in contact with the APP modified bitumen membrane, which will cause the system to delaminate.

There are currently two published ASTM Standards for APP Polymer Modified Bitumen Membranes depending on reinforcement type:

1. ASTM D-6222 Standard Specification for Atactic Polypropylene Modified Bituminous Sheet Materials Using Polyester Reinforcements. (This membrane often has the plastic film-parting agent.)
2. ASTM D-6223 Standard Specification for Atactic Polypropylene Modified Bituminous Sheet Materials Using a Combination of Polyester and Glass Fiber Reinforcements.

Suggested Performance Criteria for Smooth Surface APP Modified Membrane:

• ASTM D-6223 160 mills thick.

Suggested Performance Criteria for Granule Surface APP Modified Membrane:

• ASTM D-6223 180 mills thick.