If a chicken house has been used before and you have time, you could try the following approach we use

1.⁠ ⁠Jik in water – 250ml of Jik in 20l of water, spray the whole house, laying boxes and walls until drenched, then leave to dry. This may need 3 to 5 days depending on the weather
2.⁠ ⁠⁠Kisula (rock salt) – 1kg of salt in 10l of water, especially for the walls, corners, inside, under and behind laying boxes – then leave to dry which may need 2 to 3 days
3.⁠ ⁠⁠Use some of the commercial non-toxic disinfectants on the market

That 3-phase cycle helps us get clean out the houses and slow infection builds

When the birds are in we also disinfect spraying with a non-toxic chemical once every 2 weeks to prevent disease build-up in addition to other litter management techniques