Sound Transmission Ratings for 5 Floor Assemblies with Armoroc concrete deck panels on TOTAL JOISTS by iSPAN Systems LP
J. David Quirt, Ph.D.
13 June 2012
The objective of this study is to estimate sound transmission ratings (Sound Transmission Class according to ASTM E413 and Impact Insulation Class according to ASTM E989) for a set of five floor assemblies with TOTAL JOISTS supporting a floor deck of Armoroc fiber-reinforced concrete panels.This set of assemblies includesthe base floor assembly plus fourfloors with floor finishesinstalled over the concrete deck panels of the base assembly.
The estimates were established by extrapolation from previous acoustic tests of similar assemblies with TOTAL JOISTS, combined with data on similar generic constructions from published reports. The main report presents the STC and IIC estimates in concise tabular format. An appendix to the report gives details on the source data used, and the analysis process, to facilitate engineering assessment of the results by third party evaluators.
THE BASE FLOOR ASSEMBLY
The base floor assembly has a deck of Armoroc fiber-reinforced concrete panels supported by a TOTAL JOIST floor assembly, with insulation batts between the joists, and a ceiling of 15.9 mm fire-rated gypsum board suspended on resilient metal channels. The elements are the same as those of the specimen for NRC Contract Report B3454.1, with the substitution of Armoroc panels for USG Fortocrete panels:
|Floor Assembly||STC ( ±1 )||IIC ( ±2 )||Based on
Bare Armoroc concrete panels
|With vinyl flooring
Vinyl sheet flooring (2.5 mm thick, 0.93kg/m2) glued to the Armoroc panels
|With carpet on pad
11 mm carpet (1.9 kg/m2 ) on 9 mm carpet underlay (1.1 kg/m2) laid over Armoroc panels
|With laminate flooring on pad
8 mm Pergo engineered laminate flooring(7.3 kg/m2 )on 2 mm foam underlay (0.06 kg/m2 ) laid over Armoroc panels
|With ceramic tile on underlayment
6 mm thick ceramic tile and grout(11.3 kg/m2) on13 mm Fiberock underlayment(13.2 kg/m2) screwed tothe Armoroc panels
Table 1: Estimated sound transmission class (STC) ratings according to ASTM E413 and impact insulation class (IIC) according to ASTM E989 for the floor assemblies with flooring finishes as indicated. Note that these ratings apply to direct sound transmission through the floor assembly, in the absence of structure-borne flanking transmission (which is the rating specified in current building codes in Canada and the USA). Actual sound insulation in a building (ASTC or NNIC for airborne sound, or AIIC for impact sound) may be lower.
APPENDIX: SOURCES AND ANALYSIS
The estimates were developed by extrapolation from sound transmission data on similar assemblies – both assemblies with TOTAL JOISTS and assemblies with generic steel joists.
Reference assembly for base floor
An obvious point of reference is specimen B3454.1 (from reports on NRC contract B3454),which has Fortocrete fiber-reinforced concrete panels on 305 mm iSPAN joists (now designated as TOTAL JOISTS by iSPAN Systems LP). The components of specimen B3454.1 are identical to those of the base specimen of concern here, except that the Fortocrete deck panels are replaced by Armoroc panels in the present design.
Assessing the difference for the base floor
To estimate how the change in the physical characteristics of the floor deck would affect STC and IIC, the change was calculated using regression expressions developed by the National Research Council of Canada (NRC). NRC has performed several major studies of sound transmission through common floor assemblies, in collaboration with a broad group of industry partners. These are described in detail in NRC reportsIR-811 and RR-169, which are publicly available at http://www.nrc-cnrc.gc.ca/eng/ibp/irc/publications/index.html.A systematic analysis of the combined data from these studies is presented in RR-169. This includes regression analysis of the sound transmission results. For airborne sound transmission (STC) the regression analysis was performed on a set of 170 floors with various types of joists and gypsum board ceilings supported on resilient metal channels. For impact sound transmission (IIC), the data were separated into two sets – 144 floors with “wood” decks and 15 with concrete or gypsum concrete surfaces – because “hardness” of the top surface tends to mask dependence on other construction details. The regression analysis established dependence of the STC and IIC on variables such as mass of the surfaces, joist spacing, type and thickness of insulation, etc.
The only pertinent variable that changes between B3454.1 and the present base assembly with Armoroc is the mass of the floor deck:
On the basis of these surface densities, the regression expressions indicate that:
Thus acoustical performance should be marginally better with the Armoroc panels, but the difference is very small, so the STC and IIC ratings (which are limited to integer values)are unchanged.
Assessing the effect of added flooring
The second stage of the analysis dealt with estimating the effect of adding four common types of flooring to the base floor. The changes are quite different for the airborne and impact estimates. To perform these estimates, additional sources of data were used, including:
These comparisons, which all involve small changes from measured cases, provide the basis for credible estimates for the STC and IIC when the base floor with Armoroc is enhanced with the four types of added flooring.