Page 61 - Build 165

Moving on up
As residential buildings go higher, should typical residential claddings be used? A BRANZ research project have been investigating test methods to help answer this question.
BY GREG OVERTON, BRANZ SENIOR BUILDING PERFORMANCE ENGINEER
THE INCREASE in medium-density housing, particularly when it is also mid-rise, presents some challenges to the design community. One of these challenges is around cladding selection. Should curtainwall systems (typically associated with higher-rise buildings) be used, or can typical low-rise residential claddings simply be extended
up to buildings greater than 10 m in height?
BRANZ mid-rise façade testing project
BRANZ, in conjunction with Façade Testing New Zealand, has been assessing how residential-style claddings perform under the kind of loadings that might be expected on taller buildings. These loadings are more severe in several areas than in a normal E2/VM1 procedure: ● Higherpressures–E2/VM1isbasedonaULSpressureof2.13kPa
(associated with the extra high wind speed in NZS 3604:2011 Timber-framed buildings). Pressures up to twice this have been applied in this research.
● Seismic racking (or interstorey drift) is an optional test in AS/NZS 4284:2008 Testing of building facades to potentially introduce damage to the specimen. In comparison, E2/VM1 puts deliberate holes in the cladding at speci c locations to simulate cladding damage instead of the quasi-random damage you’d get from seismic movement.
● Air in ltration – the airtightness of the specimen is another optional part of AS/NZS 4284:2008. Aspects of airtightness performance before
A view from inside the research test booth.
and after seismic events have been assessed and the performance
compared to more severe criteria than is in AS/NZS 4284:2008.
● Pressure equalisation performance – certain façades may be speci cally designed to be pressure equalised, therefore removing
one of the forces of water entry.
Simpler and easy to build often performs better
This work aims to enable the development of test standards or Veri cation Methods in the Building Code that lead to taller
Medium-density housing
Build 165 — April/May 2018 — 59
FEATURE SECTION