What is MDH?



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Many medium-density housing developments (especially apartment complexes and mixed-use office/residential, retail/residential buildings) fall into the category of mid-rise buildings.

Mid-rise buildings are considered to be those that fall within a 10–25 m height range. With increasing densification of living within our major urban areas, the numbers of mid-rise residential or mixed-used commercial/residential buildings is likely to increase significantly to meet housing demand.

Mid-rise buildings are outside the scope of documents such as NZS 3604:2011 Timber-framed buildings and E2/AS1. This means there is a lack of available benchmark solutions that can be used to establish compliance with the Building Code, particularly clause E2 External moisture

Mid-rise buildings can be complex and are usually based on one-off specific designs. The main area of concern is where construction components, methods and details typically associated with lower building heights are being applied to mid-rise buildings.

Other considerations include the following:

  • Continuing development of skills so that construction is not being undertaken by firms with little or no experience in mid-rise construction.
  • Ensuring there is sufficient construction supervision.
  • Incorporating and verifying performance of new construction options such as CLT, off-site construction of modular sleeping, service or living units, light timber-framed acoustic and fire separations and panellised cladding systems. Designers often do not acknowledge where design details come from, and there can be a willingness to alter manufacturers’ details without getting the approval of the manufacturer.
  • How to ensure work completed on lower floors is not impacted by work on upper floors or water migrating down through the building.
  • What a design and construction quality assurance programme should look like.
  • Ensuring there is coordination between structural, fire and façade engineers.