This cooperative project amongst CLT suppliers was initiated to develop base line information on the sound attenuation performance of CLT floor and wall systems. Further, to provide baseline sound attenuation information on CLT wall and flooring systems that will allow the development of:
1. Information for building professionals to meet building code requirements.
2. Information for acoustic consultants to develop assessments on variations to the baseline tested system.
This project identifies drivers for, and barriers to, the increased use of prefabricated timber building (PTB) systems in Class 2 to 9 commercial buildings, such as apartments, hotels, office buildings and schools.
PTB systems in Australia are in a formative stage and yet to achieve broad acceptance in the marketplace as a conventional method of building.
Opportunities for PTB systems can use timber’s well-established benefits such as high strength-to-weight ratio; design and construction flexibility; general environmental credentials including carbon sequestration; and prefabrication’s suitability for use on brown-field, restricted access and difficult sites and developments. In addition legislative constraints have now been largely removed (e.g. through changes to the 2016 National Construction Code).
An increase in large scale mid-rise prefabricated buildings, and with the increasing nationalisation and internationalisation of the top tier building companies, suggests market acceptance will grow as PTB buildings are seen as ‘normal’.
The aims of this project were to investigate the Australian timber industry’s ability to benefit from the amendment to the NCC in 216, and supply products appropriate for use in timber-framed buildings up to 25 m effective height. It was also provided to equip the Australian timber industry with advice to frame fabricators and designers regarding the sawn timber products that can be readily supplied for use in frames and floors for mid-rise timber buildings. The project does not include finger-jointed M10.
Given designers can use a number of different engineering solutions to design mid-rise timber buildings. The analysis of national production of sawn timber products from 2015/16 indicates that current levels of supply should be able to accommodate an increase in demand for MGP10 and MGP12 for the following sizes 70x35; 70x45; 90x35; 90x45; 120x35; 140x45; and 190x45. The study noted that discussions between designers and truss and frame fabricators at the design stage can address potential issues of supply.
This study undertook an analysis of net benefits obtained from increasing the height allowances for the deemed to satisfy (DTS) provisions in the National Construction Code (NCC) for timber construction. The analysis considered DTS provisions for up to 25 metres for building Classes 2 and 3 (multi-residential construction) and Class 5 (office construction).
The most valuable benefit of using timber construction would be shorter construction times compared to traditional steel and concrete construction, with reduced foundation requirements; reduced need for additional services such as fixed cranes; and an increased ability for other trades to work concurrently through the construction process thereby reducing final time to completion.
The analysis estimated that using timber construction would result in cost savings of around $1.1 million for a 4 storey apartment building ($10.8 million traditional build cost reducing to $9.7 million), $1.3 million for a 5 storey apartment and $1.6 for a 6 storey apartment building assuming ten apartments per floor. For a 6 storey commercial building, cost savings of $1.92 million might be expected.
The report estimates that for the overall Australian economy, increased height allowances for timber construction in the NCC would bring approximately $103 million in net benefits over 10 years. This is made up of $98.2 million in direct construction cost savings; $3.8 million in reduced compliance costs; and $1 million in environmental benefits.