Cost categories
| Cost category | Description and key assumptions |
| 1. Formative research (software capital) | Design-focused research and piloting to identify target drivers of behaviours and the development of a comprehensive behaviour change strategy. It is conceptualised as a one-off investment with useful life of 1 year. |
| 2. Promotion (software capital) | Hygiene promotion campaign with a useful life of 5 years, and modes of delivery including: (1) house-to-house visits by promoters; (2) community/group activities and (3) mass media (online supplemental material B). |
| 3. Handwashing facility (hardware capital) | Purpose-built 20 litre drum with tap, basin and stand, with a useful life of 5 years. No capital maintenance is assumed, due to short useful life and very simple infrastructure. |
| 4. Top-up promotion (software capital maintenance) | Additional promotion activities occurring annually at 25% of initial cost (an assumption based on expert judgement), representing a lighter version of the intervention with lower frequency and dose |
| 5. Soap (recurrent) | Expenditure on soap for handwashing (ie, excluding other uses). The type of soap varied across studies but was predominantly bar soap. |
| 6. Water (recurrent) | Expenditure on water used for handwashing, assumed to average 1.5 L/person/day (online supplemental material B).47 |