Published works

This report presents the results of tests conducted to ascertain the resilience of selected building components to floodwater exposure. The experimental test programme was part of the Bushfire and Natural Hazards Collaborative Research Centre (BNHCRC) project entitled “Cost-effective mitigation strategy development for flood prone buildings”.

The motivation for this project arises from the experience and observations made during the recent flooding in Australia in 2011 and 2013, which caused widespread devastation in Queensland. The objective of the project is to address the vulnerability of existing residential building stock in Australian floodplains and is targeted at assessing cost-effective mitigation strategies to reduce the vulnerability.

Geoscience Australia as the lead researcher for the project selected the Cyclone Testing Station at James Cook University in Townville, Queensland, to conduct the experimental tests. These tests aimed to address knowledge gaps in the areas of strength and durability implications of selected components of a typical brick veneer slab-on-grade house due to immersion.

The experimental programme was developed in consultation with insurance industry loss assessors from two major companies and was scoped in recognition of the available budget. The objective of the testing was to identify whether the selected components remain serviceable following inundation and subsequent drying or whether replacement was required.

The experimental programme examined the resistance to inundation of three common building components as outlined below. For each component, a number of samples were tested to attempt to provide some understanding of the variation of resistance. For each component some specimens were tested dry without wetting and some were tested after drying following inundation. For Component 3, some specimens were also tested wet immediately after inundation.

• Component 1 (6 specimens): Tiled surfaces within a typical brick veneer, slab-on-ground house. This test examined the bond strength of floor and wall ceramic tiles to their substrate with the objective of determining the necessity or otherwise of removing and replacing all tiles following inundation.
• Component 2 (20 specimens): Manufactured timber sheet wall bracing. This test examined the effect of flooding on the racking strength of Oriented Strand Board (OSB) and High Density Fibreboard (HDF) sheet wall bracing.
• Component 3 (48 specimens): Manufactured timber joists. This test examined the effect of flooding on the bending and shear strength of manufactured HJ20045 ‘I’ section timbered joists with OSB webs.

The results of the tests showed that flooding did not have any significant effect on the pull-out strength of the bond of the ceramic floor and wall tiles to their substrate, nor on the racking strength of the OSB wall sheet bracing. There was a nominal strength reduction of 10% for the HDF wall sheet bracing when tested after wetting and drying cycle.

However, there was a significant reduction (~46%) in load carrying capacity of the timber joists when tested in the wet condition. These results suggest that the samples whilst in the wet stage may be compromised due to reduced strength capacity and stiffness. However, if allowed to dry then the specimen could recover to nominally 96% of average strength capacity and stiffness. Moreover, it was observed that the moisture content level after the test returned close to pre-inundation level within a week and therefore contributed to recover the strength and stiffness.

The results of the testing will inform recommendations on mitigation measures within the BNHCRC flood project. The results will also inform the selection of building materials for new construction in flood-prone areas.