Background Injuries due to falls in the home impose a huge social and economic cost on society. We have previously found important safety benefits of home modifications such as handrails for steps and stairs, grab rails for bathrooms, outside lighting, edging for outside steps and slip-resistant surfacing for outside areas such as decks. Here we assess the economic benefits of these modifications.

Methods Using a single-blinded cluster randomised controlled trial, we analysed insurance payments for medically treated home fall injuries as recorded by the national injury insurer. The benefits in terms of the value of disability adjusted life years (DALYs) averted and social costs of injuries saved were extrapolated to a national level and compared with the costs of the intervention.

Results An intention-to-treat analysis was carried out. Injury costs per time exposed to the modified homes compared with the unmodified homes showed a reduction in the costs of home fall injuries of 33% (95% CI 5% to 49%). The social benefits of injuries prevented were estimated to be at least six times the costs of the intervention. The benefit–cost ratio can be at least doubled for older people and increased by 60% for those with a prior history of fall injuries.

Conclusions This is the first randomised controlled trial to examine the benefits of home modification for reducing fall injury costs in the general population. The results show a convincing economic justification for undertaking relatively low-cost home repairs and installing safety features to prevent falls.

Trial registration number ACTRN12609000779279.