Template:Part 8 (Waterproofing Roofs - SBS)

1 General

1. Insulation overlay boards are installed in most conventionally insulated roof assemblies to
   1. protect heat-sensitive insulation materials from damage by heat and flame.
   2. protect insulation materials from accidental impact.
   3. provide dimensional stability to the roof system.
   4. distribute dead loads from heavy overburdens or equipment installed on top of the finished roof assembly.
   5. ensure the membrane performs as it should.
   6. provide a suitable substrate for membrane application.
2. Insulation overlay boards may be mechanically attached or adhered, depending upon the insulation type and the design requirements of the roof assembly as a whole. See more information on Insulation Joints and Overlays in Essential Elements.

1.1 Design

1.1.1 RoofStar 15-Year Guarantee

1. An insulation overlay is required for all insulated systems, regardless of the insulation type, and overlays must
   1. be at least 6.4 mm (1/4”) thick.
   2. possess a compressive strength of at least 690 kPa (100 psi).

1.1.2 All Projects

1. An insulation overlay of one or more layers is required over all board-type insulation when
   1. the compressive strength of the insulation is less than 110 KPa (20 psi).
   2. the membrane will be applied with a torch flame, adhesives or hot bitumen.
2. When heat-sensitive insulation materials are used in a roof assembly, they must be covered with a heat-resistant insulation at least 50 mm (2”) thick. This requirement does not apply to crickets manufactured from heat-sensitive insulation and installed above the insulation assembly or on an uninsulated supporting deck structure, since the crickets serve only to promote drainage. However, a minimum overlay of flat board heat-resistant insulation measuring at least 50 mm (2”) thick is strongly recommended. See also 7.1.2 Design.
3. When torch-applied or hot-mopped membranes are specified for installation above crickets made from heat-sensitive insulation, the crickets must be protected from heat damage with insulation overlays. See also 8.3 Application.
4. While minimum insulation panel thicknesses are permissible for some designs, the Design Authority may consider the constructability of the roof system from a material handling perspective. Therefore, when material are by their nature breakable, the specifier should consider specifying a thicker panel.
5. A conventionally insulated roof assembly supporting an overburden must be designed with at least one layer of adhered composite insulation overlay
   1. no less than 12.7 mm (½") thick.
   2. with a minimum compressive strength of 620 kPa (90 psi).

   
   See also 14.1.2.1 General

2 Materials

See Insulation Overlays accepted for use in RoofStar Guaranteed roof systems.

Table 8.1 Insulation Overlay Minimum Thicknesses

Material	Minimum Thickness - mm (in.)
Asphaltic core board	4. 8 (3/16")
Moisture-resistant gypsum core board	6.4 (1/4")
High-density Insulation Board	12.7 (1/2")
Composite and Laminated Overlay Board	6.4 (1/4")
Fibreboard	As listed in this Manual
Membrane-laminated overlays	As listed in this Manual
Mineral wool	As listed in this Manual

1. Regardless of the type of insulation overlay, the overall thickness of insulation overlay boards shall not exceed 50 mm (2”). Minimum allowable thicknesses are shown in Table 8.1 above.
2. Asphalt or paraffin-impregnated coated fibreboard roof insulation adhered with hot asphalt or an asphalt-based adhesive must be asphalt-coated on the top and bottom surface (minimum coated two-sides).
3. Fire guard tape must be 150 mm (6”) wide
   1. self-adhering modified bituminous tape acceptable to the membrane manufacturer.
   2. Type IV fibreglass felt or No. 15 organic felt, applied with hot bitumen or cold adhesive.

3 Application

3.1 General

3.1.1 RoofStar 15-Year Guarantee

1. See the requirements for a RoofStar 15-Year Guarantee in 8.1.1.1.

3.1.2 All Projects

1. An insulation overlay of one or more layers is required over all board-type insulation when
   1. the compressive strength of the insulation is less than 110 KPa (20 psi).
   2. the membrane will be applied with a torch flame or hot bitumen.
2. Heat-sensitive insulation and crickets must be protected from exposure to torch flame or hot bitumen with overlay panels. This may be accomplished with
   1. one layer of panels,
      1. at least 12.5 mm (1/2”) thick.
      2. offset from insulation joints by at least 300 mm (12”).
      3. continuously sealed with a flame-impervious tape along all joints with adjacent panels|| 2020-July-3 }}.
   2. two layers of panels,
      1. each at least 4.8 mm (3/16”) thick.
      2. offset from each other, from the adjacent layer, and from insulation joints by at least 300 mm (12”)
3. When multiple layers of an overlay board are specified, the joints between boards must be offset/staggered at least 300 mm (12") from adjacent layers and rows. See Figure 8.1. See also 7 INSULATION .
   

   Figure 8.1

   
   

4. When mechanically attaching insulation overlay boards, the insulation and overlay boards may be fastened together as one assembly. Unless otherwise indicated by the system requirements in a Tested Assembly, follow the fastener patterns set out in 3 SECURING the ROOF ASSEMBLY.
5. When a composite overlay with an integrated base membrane is mechanically fastened over insulation, fasteners and plates used in the field of each panel must be covered with torch-applied polyester or composite-reinforced membrane patches that extend past the edge of each plate at least 50 mm (2”).
6. Insulation in a conventionally insulated roof assembly supporting an Overburden must be overlaid with at least one layer of adhered composite insulation overlay
   1. at least 12.7 mm (½") thick.
   2. with a minimum compressive strength of 620 kPa (90 psi).

   See 14 The ROOF as a PLATFORM for design and construction standards.

7. Fibreboard shall not be used with torch-applied membranes.
8. An insulation overlay is not required when the base layer of the primary roof membrane is mechanically attached, provided the insulation is heat-resistant and has a compressive strength of 110 Kpa (20 psi).

3.2 Overlaying Heat-resistant Insulation

1. An insulation overlay is not required over heat-resistant insulation
   1. unless the
      1. compressive strength of the top layer of insulation is less than 110 KPa (20 psi).
      2. insulation is mineral wool and is mechanically fastened through the uppermost insulation layer.
   2. when the top layer in a multi-layered insulation assembly is adhered bitumen-faced mineral wool insulation.
2. When an overlay board is required over mineral wool insulation, the overlay board must be a moisture resistant gypsum core board measuring at least 12.7 mm (1/2") thick. See also 7.2 concerning Mineral Wool Insulation.
3. A single layer of insulation overlay is acceptable when an overlay is specified for heat resistant insulation.

3.3 Overlaying Heat-sensitive Insulation

1. When the roof membrane is applied with heat or hot bitumen, heat-sensitive insulation in the primary thermal assembly must be overlaid with a layer of heat-resistant insulation at least 50 mm (2”) thick. See 7.1.2.2(5) and 8.3.2 above.
2. When EPS crickets are specified and installed, a minimum overlay of flat board heat-resistant insulation measuring at least 50 mm (2”) thick is strongly recommended. See also 7.1.2.2(9).