Roof assemblies: lighter fill, coordinated design.
For new construction or rehabilitation, BLC may be considered as lightweight fill beneath a roof system designed for the project.
Where the material may fit
Level adjustments, void filling and a thermal function are potential uses. Evaluate BLC against added mass, available depth and placement conditions. The designer defines slopes and outlets; these do not follow from material fluidity alone.
The load-bearing deck supports the loads. The roof design then assigns each layer its function: air and vapour control, insulation, any separation layer, waterproofing and protection. BLC fill is not a waterproofing membrane.
Added mass: three thickness examples
| Illustrative thickness | Dry | Fresh | After immersion |
|---|---|---|---|
| 25.4 mm | 14.2 kg/m² | 14.8 kg/m² | 15.9 kg/m² |
| 50.8 mm | 28.4 kg/m² | 29.7 kg/m² | 31.8 kg/m² |
| 100 mm | 55.9 kg/m² | 58.4 kg/m² | 62.6 kg/m² |
Mass per area = density × thickness in metres. Values rounded to 0.1 kg/m² using the BLC batch of 15 July 2014: 559 kg/m³ dry, 584 kg/m³ fresh and 626 kg/m³ after immersion (MTQ report, PDF page 5).
Review BLC test reportsThese thicknesses illustrate mass calculations only. They are neither specified minimum thicknesses nor allowable loads. The immersion values reflect the test, without defining service moisture on their own. Include the other layers, water, snow, equipment and construction loads in the assembly assessment.
Moisture, drying and interfaces
Account for initial moisture, rainfall during construction and drying conditions before enclosing the assembly. Verify compatibility with the membrane, adhesives and other components with those responsible for the system.
Detail low points, outlets, upstands, penetrations and maintenance access. Thermal conductivity measured on dry material does not by itself establish the thermal resistance of the complete roof.
Prepare a roof assessment
Provide drawings, deck condition, areas, proposed depths, drainage levels and access constraints. The designer checks permanent and temporary loads, deflection, hygrothermal behaviour, fire requirements and interfaces.
BLC data provide a starting point. Qualification of the roof system, its installation and its warranties must be established for the selected assembly.