Multi-unit residential buildings in timber, the New Zealand experience
Authors: Tonks, Garrick M.
ABSTRACT: This paper discusses the emergence of timber as a prime construction material used in
low-rise multi-storey multi unit residential development. Historically residential timber buildings were
limited to two and a half floors under the light timber codes, and further limited to concrete ‘fire proof’
inter-tenancy walls. Fireproofing is no longer restricted to concrete, and design methods have
recognized the potential to build beyond 2-3 floors. Currently timber buildings are being constructed to
five floors. Generally these buildings are constructed from small section gauged timber, with the
occasional building utilizing post and beam construction. Both design approaches are discussed by
reference to existing buildings, as are the approaches taken by the New Zealand codes/industry. The
major problem facing timber utilization in multi-residential building is sound transmission, particularly
over the low frequency range. While the current code requirements for sound attenuation are met,
building users report undesirable levels of ‘neighbour noise’. The acceptable level of sound
transmission is under review, and the expected recommendations will see the requirements increased.
This change will place greater demands on timber buildings, demands that exceed present
construction practice. Current New Zealand research on sound transmission is presented and reviewed.