| Quality management certification | A current ISO 9001 certificate covering the relevant manufacturing activities | Certificate number, issue date, expiry date, certified scope, certification body, and accreditation details | Confirm the certificate directly through the certification body or its public certificate database | Certificate may be expired, altered, suspended, or unrelated to modular construction | Reject until independently verified |
| Certificate scope | Scope must include design, fabrication, assembly, or another activity directly relevant to the ordered unit | Full certificate and scope statement, not only an ISO logo or marketing page | Compare the certificate scope with the purchase specification and production process | A valid certificate may not apply to the products being purchased | Require clarification or reject |
| Factory audit history | At least one recent independent factory audit, preferably completed within the previous 12 months | Audit report, audit date, auditor qualification, site covered, findings, corrective-action plan, and closure evidence | Check whether findings are supported by photographs, records, responsible persons, and completion dates | Undisclosed subcontracting, weak process control, or unresolved safety and quality issues | Hold approval pending audit |
| Corrective actions | All major and critical findings must have documented root-cause analysis and verified closure | Corrective-action reports, revised procedures, training records, and follow-up verification | Confirm that closure evidence addresses the cause, not only the visible symptom | Repeated defects, delayed delivery, and unreliable quality performance | Do not release purchase order |
| Material traceability | Traceable records for structural steel, panels, insulation, windows, doors, electrical items, and plumbing components | Material certificates, batch or heat numbers, incoming inspection records, and supplier records | Trace a sample finished unit back to purchase records and inspection results | Unapproved substitutions and difficulty proving conformity after delivery | Approve only with documented controls |
| Welding and structural control | Approved drawings, qualified welding procedures, competent welders, and recorded inspections | Welding procedure documents, welder qualification records, inspection reports, and nonconformance records | Review records and inspect representative frames or arrange a third-party inspection | Deformation, corrosion exposure, transport damage, or structural performance problems | Require technical review before approval |
| Production capacity | Capacity must match the agreed quantity, delivery schedule, and required quality-control checkpoints | Production plan, monthly capacity statement, current order loading, equipment list, and staffing plan | Compare claimed capacity with observed work-in-progress, floor space, equipment, and staffing | Late delivery, rushed work, uncontrolled outsourcing, and incomplete inspections | Use phased orders and milestones |
| Quality inspection plan | Documented inspections for incoming materials, in-process work, final assembly, waterproofing, electrical, and plumbing systems | Inspection and test plan, checklists, test results, calibrated equipment records, and release approval | Match inspection records to serial numbers, drawings, and contractual acceptance criteria | Defects may remain hidden until installation or occupancy | Approve with hold points |
| Subcontractor management | All outsourced processes must be disclosed, controlled, and included in the quality system | Approved subcontractor list, process-control records, inspection reports, and subcontracting agreements | Audit critical subcontractors or require equivalent independent inspection | Inconsistent quality, unclear responsibility, and reduced traceability | Reject undisclosed outsourcing |
| Pre-shipment inspection | Final inspection completed before shipment, with defects corrected or formally accepted | Signed inspection report, photo record, packing list, serial-number record, and open-issue register | Use an independent inspector and make shipment conditional on approval | Damage, missing components, and costly remedial work after arrival | Release shipment after approval |
| Document control | Only approved, current drawings and specifications may be used in production | Revision-controlled drawings, bill of materials, change records, and approval history | Compare production documents with the signed purchase specification and approved samples | Unapproved design changes, incorrect components, and disputes over responsibility | Stop production until corrected |
| After-sales support | Written warranty, spare-parts process, response times, and installation support must be contractually defined | Warranty terms, service procedure, spare-parts list, escalation contacts, and defect-response records | Include measurable response and remedy obligations in the purchase contract | Long resolution times and high replacement or repair costs | Use contractual protection |
