Insulation Joints and Overlays

1 General

Insulation overlays are used to separate the roof membrane from the primary insulation, usually for one of two reasons:

• to prevent the insulation from affecting the performance of the roof membrane
• to prevent the roof membrane and / or the method of application from affecting the insulation

The insulation can affect the performance of the roof membrane in the following ways:

• the insulation may be incompatible with the membrane, resulting in a loss of physical properties
• different coefficients of thermal expansion may result in membrane splits / cracks.

The roof membrane and / or the method of application can affect the insulation in the following ways:

• the insulation may not be capable of withstanding asphalt application temperatures and may “burn-out”
• some insulations will not accommodate direct torch-applied membranes
• insulations that are too “soft” may result in delamination or damage to the membrane or insulation when exposed to heavy loads or traffic
• the solvents and adhesives used for flexible membranes may adversely affect the insulation.

NOTE: All hot asphalt-adhered asphaltic membranes (built-up roofing, modified bitumen, etc.) require an insulation overlay over heat sensitive insulations and heat insensitive foamed insulation. RGC Guarantee Standards for heat sensitive insulations require a two-layer overlay board for a five (5) or ten (10) year Guarantee. RGC requires the use of a two-layer overlay board over heat sensitive insulations in all cases, and also requires a single-layer overlay board application over heat insensitive insulations for all hot asphalt-adhered membranes. For single-ply, non-asphaltic membrane roofing systems, the membrane manufacturer should be consulted for proprietary options.

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1.1 Insulation Joint Tape

Where RGC Guarantee Standards or the roof system specification calls for taping fibreboard or insulation joints, consult the list of Accepted Materials section of this Manual:

1.2 Asphalt and Paraffin-Impregnated / Coated Fibreboard Roof Insulation and Insulation Overlay Board

Under construction

1.3 Proprietary Overlay Boards

Under construction

2 Materials

To view materials accepted for use in the RoofStar Guarantee Program, see Accepted Materials: Insulation Overlay Board.