Case study / Construction
A mobile app that puts each job in the operative's hand, works with no signal at all, and feeds the contractor's existing back-office system without replacing it.
01 / The industry
Building contractors working for councils, housing associations and other property owners take on new build, roofing, refurbishment, adaptations, and planned and responsive maintenance. Much of it happens in occupied homes, basements, stairwells and blocks of flats, where mobile signal is weak or missing.
Every job needs evidence: photos, arrival and departure times, the work done against a schedule of rates, and notes for the client and for invoicing. The people doing it are a mix of in-house operatives, contract managers and subcontractors.
02 / The problem
The contractor ran on a no-code back-office system, with a web portal for its operatives and subcontractors and a layer of integrations on AWS. It worked well in the office. On site it did not: there was no offline support, and the platform's own mobile option could not work without signal either.
So some operatives printed their documents before setting off, photos and updates went by WhatsApp and email for the office to re-key, and the office rang subcontractors to ask how jobs were going. Updates arrived late.
The app had to work with the back office, not replace it.
03 / What we built
We started with a feasibility study, then designed the app with the client over five rounds of reviews before building it: one codebase for iOS and Android.
The design goal was that every flow can be finished end to end in aeroplane mode, including completing a job and sending a message with photos.
04 / How it works
Each phone holds an encrypted database of the operative's jobs, with the key kept in the phone's secure keychain. Everything a user does is saved on the phone first and shows straight away, then joins a queue that sends changes in order whenever there is a connection, retrying with growing gaps between attempts. The queue survives the app being closed. Signing out wipes the key first, then the data and photos.
Photos are resized, stripped of their location metadata and watermarked on the phone, then uploaded straight to storage, picking up where they left off if the connection drops.
The app never talks to the back-office system directly. A gateway on AWS Lambda, defined in Terraform, handles sign-in, syncing and every write, and only makes the kinds of change on its allow-list. Sync fetches only what has changed since the phone last checked, when the app opens, every few minutes, in the background and when a notification arrives.
When the office and the phone have both changed the same detail, a rule for that kind of change decides. Where it matters, such as an appointment time, the phone shows which fields changed and lets the operative choose. Overriding the office's version is logged.
Operatives sign in with their existing portal account and a text message code, then Face ID or a passcode. Sessions are short-lived and renewed automatically, every device is registered, and sign-ins are rate-limited and recorded. Signing in on a phone never signs anyone out of the desktop portal.
05 / Where it is now
The build went from first commit to a feature-complete beta in about nine weeks, against a fixed plan. The client began acceptance testing in October 2026, with test builds on iPhone and Android and updates delivered over the air. Release to the app stores follows testing on real phones.
06 / More work
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A commercial fit-out contractor's project and finance data sat in a decade-old system with fixed reports. We built live dashboards into it for forecasting, work in progress and daily changes, plus wallboards in its offices.
07 / Contact
Tell us what your people do on site today, and what happens to the information afterwards.