Reinforcement or upgrading of existing physical structures to become more resistant and resilient to the damaging effects of hazards.


1. Retrofitting requires consideration of the design and function of the structure, the stresses that the structure may be subject to from hazards or hazard scenarios, and the practicality and costs of different retrofitting options.

2. Examples of retrofitting include adding bracing to stiffen walls, reinforcing pillars, adding steel ties between walls and roofs, installing shutters on windows, and improving the protection of important facilities and equipment. See also "Corrective disaster risk management".

3. Retrofitting may sometimes be referred to as “Hardening".


Modified from UNDRR Sendai Framework Terminology on Disaster Risk Reduction (2022).


Eco-Roof retrofit in Portland to reduce urban flooding risk

Urban runoff is a major contributor to water pollution and flooding in urban communities across the globe, with roof surfaces accounting for a significant portion of impermeable areas in urban regions. Retrofitting roofs presents an excellent opportunity to reduce urban runoff, and the Amy Joslin Memorial Building in Portland, Oregon, serves as an excellent example. Situated on the confluence of the Columbia and Willamette rivers, Portland is particularly vulnerable to flooding, and the 16,000 square foot roof retrofit provided a prime opportunity to address this issue. The extensive green roof garden captures stormwater, reduces energy demands, and provides a habitat for insects and birds. Over an 18-month period, the green roof reduced peak flow by 86 percent, run-off by 25 percent, and reduced air conditioning loads by 5-10 percent. By demonstrating the viability of retrofitting, Portland's project highlights the potential for such measures to enhance community resilience, reduce pollution, and foster sustainable urban growth.



  • Lamond, J. E., Wilkinson, S. J., Rose, C. B., & Proverbs, D. G. (2014). Sustainable Urban Drainage – Retrofitting for Improved Flood Mitigation in City Centres. Royal Institution of Chartered Surveyors. Retrieved December 27, 2022.
  • Lamond, J. E., Rose, C. B., & Booth, C. A. (2015). Evidence for improved urban flood resilience by sustainable drainage retrofit. Proceedings of the Institution of Civil Engineers-Urban Design and Planning, 168(2), 101-111.
  • Stovin, V. (2010). The potential of green roofs to manage Urban Stormwater. Water and Environment Journal 24(3): 192-199.