Sound-transmission-class (STC) and fire-resistance (FR) ratings for many of the generic construction assemblies traditionally used in construction of Canadian housing and small buildings have been published in the National Building Code of Canada (NBCC) since 1950. While some of those ratings were updated over the intervening years, many of them had not been revised since 1965. Therefore, in 1992 the Canadian Commission for Building and Fire Codes decided to delete from the 1995 edition of the NBCC, every STC and FR ratings that could not be supported by contemporary data.
Canadian architects, fire-protection engineers and building officials make extensive use of the STC and FR ratings in the NBCC when designing and approving housing and small buildings in Canada. The STC ratings are also used extensively in the design of engineered structures. Wood-frame assemblies, more than any other, are designed and constructed in accordance with the STC and FR ratings listed in the NBCC. Therefore, it was crucial for the wood industry to generate the necessary data to retain STC and FR ratings for wood-frame assemblies. No single organisation in Canada could afford to bear the costs associated with a testing program to determine STC and FR ratings for all assemblies commonly used in Canadian housing and small buildings. Therefore, a partnership of affected industries and governmental organisations was created, and the National Research Council Canada (NRC), in collaboration with those partners, commenced a research program to quantify STC and FR ratings for generic building assemblies protected by gypsum board. Forintek Canada Corp., in conjunction with the Canadian Wood Council, and a number of North American manufacturers of engineered wood products, is participating in that program on behalf of Canada’s wood products industry. This report describes progress achieved in that research program between April 1, 2000 and March 31, 2001.
A paper entitled “Observations on fire-endurance tests of wood-frame assemblies protected by gypsum board” was presented at the 4th International Wood & Fire Safety Conference in ÒrbskJ Pleso, Slovak Republic. A paper entitled “Sound-transmission-class and fire-resistance ratings for wood-frame floors” was published in Fire and Materials. A 26-page paper entitled “Thoughts and observations on fire-endurance tests of wood-frame assemblies protected by gypsum board” was submitted for publication in Fire and Materials.
The second meeting of the steering committee for the collaborative research project to assess fire and acoustical performances of floor assemblies was held on September 12, 2000. When completed, the total value of the work carried out for this part of the overall collaborative testing program will be about $2,200,000. NRC is contributing 40%. The wood industry is contributing about 20%.
There are no differences in the fire endurance times of floor assemblies constructed with nominal 2x8’s, compared to those for assemblies constructed with nominal 2x10’s, provided all other construction details are identical and applied structural loads are proportionally the same. The addition of 25-mm thick gypsum-concrete toppings (1957 kg/m3) on wood-frame floors does not reduce the fire endurance of the floor. There are no differences in the fire endurance times of wood-frame floor assemblies having ceilings constructed with two layers of gypsum board, irrespective of whether the gypsum board is fastened directly to the bottom of the joists or attached to the bottom of the joists using resilient channels.
Attempts to design wood-joist floor assemblies having 45-min fire-resistance-ratings were unsuccessful when there was no insulation between the joists and the ceiling consisted of a single layer of gypsum board. Similarly, attempts to design wood-joist floor assemblies having 1-hr fire-resistance ratings failed when the ceiling consisted of only one layer of gypsum board and rock-fibre insulation was placed between the joists.
The third meeting of the steering committee for the Phase-II collaborative research project to assess flanking sound transmission in multifamily dwellings was held on June 13, 2000. The fourth meeting was held at USG’s Research and Technology Center on October 12 and 13, 2000.
When acoustical performance is considered, and particularly impact-noise-transmission, wood-frame construction has an almost insurmountable advantage over heavy concrete.
A meeting of the steering committee for the collaborative research project to assess fire and acoustical performances of wall assemblies was held on September 13, 2000.
The results of fire tests on wood-frame walls were reported in two Internal Reports published by NRC. The first draft of a NRC Internal Report on the acoustical testing carried out for this project has been written.
A representative of Forintek attended meetings of the AF&PA Subcommittee on Fire Performance of Wood, and the AF&PA Technical Committee from August 8 to 10, 2000.
AF&PA funded a series of fire endurance tests on wood-frame walls. By selecting only the strongest studs and using specially selected Type X gypsum board, they were able to achieve greater fire resistance ratings for wood-stud walls than were observed in the collaborative project described in this report.
This research project will continue in 2001/2002. Forintek will continue to write papers for presentation at conferences, seminars and workshops and for publication in journals and other written media in order to get the message out about this project and the acoustical and fire performance of wood-frame construction. One of the major points that will be made in those papers is that wood-frame construction provides superior sound insulation, compared to concrete assemblies, and that it is less expensive to construct acoustically superior wood-frame assemblies than steel-frame ones. In addition, Forintek will work with CMHC and NRC to develop a “best-practice” guide describing construction details for party-walls separating adjacent units in multifamily dwellings.