A job file is not a folder structure. It is the live record that survives people leaving site, clients changing their minds, and month-end reviews.
At minimum you need: a dated site diary with photos; a current drawing register with revision control; snag and variation registers with evidence; H&S records tied to the job; CIS and retention on the commercial side; and a client-facing view for progress and sign-off without exposing the whole file.
Enterprise platforms cover much of this but punish SMEs with per-seat pricing and long onboarding. Spreadsheets and WhatsApp cover none of it reliably when something goes wrong.
SiteOS is built around that checklist for UK builders: one company price, unlimited people and projects, with offline site capture and UK commercial rules in the product - not as an integration project.