ASTC; high rise; steel stud; SilentFX QC; CertainTeed; NBCC
The 2015 edition of the National Building Code of Canada (NBCC) introduced significant changes to the acoustic requirements for residential constructions. The 2015 edition of the NBCC changes the acoustic requirements for residential constructions from requirements based on a Sound Transmission Class (STC) rating to requirements based on an Apparent Sound Transmission Class (ASTC) rating. The ASTC rating includes contributions from both the direct transmission through the common building element as well as flanking transmission through the attached junctions and elements. The ASTC rating is therefore a better metric than the STC rating for describing the sound insulation of a building construction. The 2015 NBCC requires an ASTC rating ≥ 47 for constructions between dwelling units. The ASTC rating that a building constitution will achieve depends on the design of the building elements including the gypsum board, the framing and the thermal insulation as well as the design of the junctions between the building elements. Changes to the building elements or the junctions may change the ASTC rating. This report includes twenty-two examples of the calculation of the ASTC rating for lightweight (25 gauge) steel stud walls typically used high-rise constructions in conjunction with concrete floors and ceilings. The gypsum board installed on the lightweight steel stud walls in the examples includes combinations of 15.9 mm (5/8”) SilentFX® QuickCut gypsum board and 15.9 mm CertainTeed Type X gypsum board directly fixed to the steel studs. The examples include both lightweight and concrete masonry façade walls. All of the constructions shown in the examples achieved an ASTC rating of 47 or greater.