The Argument
Once reuse is framed as a question of evidence, it stops being only an engineering problem and becomes an information problem. That is the position Professor Ghaffarian takes into the interview, and in his view it is where the next decade of the field will be decided. Two consequences follow. Condition, not material category, decides a component’s future: the same timber stud behaves very differently after a cyclone than after three days in floodwater. And volume is not opportunity, because the more violent the event, the less of its material remains fit for its original purpose.
Prof Ghaffarian points to New Zealand’s own record, from the Canterbury earthquakes to the 2023 Auckland floods, where high rates of diversion from landfill have sat alongside far smaller returns of recovered material to consented homes. His conclusion is that the sector measures the wrong success. It counts what was saved from the tip, when it should count what goes back into safe, certified buildings at close to its original value.
The Evidence Base
The interview draws on Material Recovery and Reuse in Post-Disaster Housing Reconstruction: Lessons from Global Disaster Contexts, published in Buildings in 2026. The review brings together two literatures that rarely meet: disaster studies, which think in tonnes and days, and circular construction research, which thinks in condition and value but mostly studies calm, planned demolition. Only 20 studies addressed material recovery in disaster settings directly, so the authors added 49 studies of transferable engineering evidence, keeping the two tiers separate. Decay, corrosion and the test methods that detect them behave the same way in both settings; urgency, contamination, unknown loading history and missing drawings do not.
That separation exposes a gap. Some of the most developed reuse guidance excludes steel that has seen extreme loading, fire or plastic deformation, which means it was written for buildings that did not have a disaster. Prof Ghaffarian argues that protocols written specifically for disaster exposed materials, steel that has yielded, timber that has been submerged, concrete that has been shaken, are the field’s most pressing need, and that New Zealand is well placed to write one.
From Assessment to Decision
Condition based assessment, as the framework sets it out, asks three questions of every component: what happened to it, what it is now, and what it will be asked to do. It becomes a matching exercise between what a material can still prove and what its next use demands. The difficulties are practical and regulatory: hidden damage that only destructive testing reveals, timber that turns from salvageable to mouldy within days, the logistics of testing thousands of components, and a Building Code that expects structural elements to last at least 50 years while buildings keep no record of their own history.
Where the factors conflict, the framework treats some as gates and others as dials. Health, safety and structural integrity for load bearing use are gates and are never traded against carbon or cost; durability, cost and appearance are dials that decide where a material goes. When a gate closes, Prof Ghaffarian’s answer is to downgrade the use, not the material, so that a beam unfit for primary structure can still serve as a lintel, a joist or a fence panel. He is candid that the framework is conceptual, and that the next step is a decision model that updates as test results arrive. He also names a conflict engineering cannot settle: materials from places of loss carry meaning, and in Aotearoa any recovery programme should ask communities, and mana whenua in particular, how they feel about reusing them.
Implications for Policy
For agencies weighing a recovery mandate, his advice is to mandate the assessment rather than the outcome: require that recoverable material is assessed before it is crushed or buried, then let the evidence decide where it goes. Five conditions make that work: a plan agreed before the disaster, including clear rules for the first 72 hours; a certification pathway for recovered products; liability and insurance shared fairly between those who sign off and those who benefit; a market, ideally with public clients committed in advance; and a measure of success based on reuse in consented buildings rather than diversion alone.
The longer term answer connects to his work on digital twins. If every new building carried a digital record of its materials, a material passport, the assessor after the next disaster would not start from zero. Prof Ghaffarian sees Europe moving in that direction through digital product passports, and argues that New Zealand should act before the next flood rather than after it. The argument sits alongside the forthcoming Elsevier volume Digital Twins for Sustainable Cities.
The Platform
Faculti is a research dissemination video platform and a member of Crossref, so each interview receives a DOI and can be cited as a research output. The interview is a recorded conversation of 20 to 25 minutes with questions set in advance. The recording date is to be confirmed, and the entry will link to the published interview and its DOI once released.