Key takeaways
- Check the business licence on China's national enterprise credit system: a manufacturer's scope lists production of aluminium products or doors and windows, not only sales or import-export.
- A real test report has a lab name, report number, date, specimen size and results by class, and the lab confirms it when you email them the report number.
- Ask for a live, unscripted video audit of at least 60 minutes covering extrusion, coating, CNC, assembly, testing and packing, and request a named profile be cut on camera.
- A third-party pre-shipment inspection under ISO 2859-1 at general inspection level II, with AQL 0 critical / 2.5 major / 4.0 minor, is a sensible default for windows.
- Treat refusal of an unannounced video call, test reports in another company's name, or prices more than 25% below the market as reasons to stop.
To audit a Chinese window factory, verify three things in order: the legal entity actually manufactures (licence scope and owned premises), it controls the critical processes (extrusion or profile sourcing, thermal-break rolling, coating, fabrication and testing), and its test reports trace to an accredited lab for the exact system you will buy. A structured video audit plus a sample corner and a lab check takes about two weeks and costs far less than one rejected container.
Manufacturer or trading company?
Trading companies are not inherently bad — some add real value in consolidation — but they typically add an 18–35% margin, cannot commit to production slots and often show test reports belonging to someone else. Lead times quoted by traders are commonly 45–70 days versus 25–35 days direct. The first job of an audit is to establish which one you are talking to.
- Business licence: every Chinese company has an 18-character Unified Social Credit Code. Look it up on the National Enterprise Credit Information Publicity System and check the registered name, capital, address and business scope.
- Scope wording: a manufacturer's scope includes production or processing (生产 / 加工) of aluminium profiles, doors and windows or curtain wall; a pure trader lists sales (销售) and import-export only.
- Address match: the registered address, the factory you see on video and the shipper on previous B/Ls should match or be explained by a documented group structure.
- Bank account: the beneficiary on the proforma invoice must be the same legal entity that signs the contract and appears on test reports.
What to see on the shop floor
A vertically integrated window maker runs extrusion presses, thermal-break rolling, a coating line and CNC fabrication. Many good fabricators buy profiles instead of extruding; that is acceptable if they name the extruder, the alloy (normally 6063-T5 or T6) and can show mill certificates. ARCVIEW, for reference, runs six presses from 880 to 3,600 t, a vertical Qualicoat-approved powder line and 28 CNC centres — the about page shows the plant.
| Area | What to ask to see | Evidence of control | Red flag |
|---|---|---|---|
| Extrusion | Press running, die store, billet stock | Billet certificates, ageing oven logs, wall-thickness checks | No presses and no named profile supplier |
| Thermal break | Rolling / knurling machine | Shear-strength test records per batch | Strips pushed in by hand, no test records |
| Coating | Pre-treatment tanks, booths, curing oven | Qualicoat or equivalent licence; film thickness 60–80 µm logged | Coating outsourced with no supplier named |
| CNC and cutting | Double-head saws, machining centres | Cut tolerance checks (e.g. ±0.3 mm), calibrated tapes | Manual saws only for large-volume claims |
| Assembly | Corner crimping, gasket insertion, glazing | Corner glue injection, glazing blocks, unit labels | Unlabelled stock, no shop drawings on benches |
| Testing | Water-spray rig, in-house test chamber | Test records by unit tag or batch | No testing equipment at all |
| Packing | Crates, film, corner guards | ISPM-15 compliant packing, crate labels per drawing | Loose units wrapped only in film |
| Engineering | Drawing office, software in use | Named engineers, sample shop drawing, structural calcs | Drawings prepared by the client only |
Test reports that trace to a lab
Ask for full reports, not certificates or logos. Check that the report names the applicant (ideally the factory itself), the tested system and series, specimen size, glass and hardware, the test standard and the results by class. Then email the lab with the report number and ask it to confirm authenticity. For product certifications such as NFRC, the listing can often be checked in the certifying body's public directory; ISO 9001 certificates can be checked with the issuing body or via the IAF CertSearch database. Our guides to CE marking and NFRC and NAFS explain what each report should contain, and the certifications page lists ARCVIEW's report numbers.
Sample corner sections
A 300 × 300 mm corner sample is the cheapest audit tool. Cut it with a saw on arrival and measure wall thickness with a calliper — structural walls of 1.4 mm or less on a heavy door system are a warning; quality systems commonly use 1.8–2.2 mm. Check the polyamide strip is PA66 GF25 and firmly knurled, gaskets are EPDM rather than PVC, corners are crimped and glued, and the coating has even thickness on hidden faces. Compare the sample with the profile drawings in the quotation.
Red flags
- Test reports issued to a different company, or results for a system the factory does not list in its catalogue.
- Refusal of short-notice video calls, or calls that only show offices and showrooms.
- Prices more than 25% below comparable manufacturers for the same glass and hardware.
- Payment requested to a personal account or an entity different from the contract party.
- No shop drawings offered before deposit, or reluctance to put sizes and specifications in the contract.
Third-party inspection and AQL
For the first order, book an independent inspection by a firm such as SGS, Bureau Veritas or Intertek, or a qualified local inspector. A factory audit checks capability; a pre-shipment inspection checks your goods. Sampling is normally to ISO 2859-1 at general inspection level II. A typical window plan is AQL 0 for critical defects (glass breakage, missing safety labels, wrong glass type), 2.5 for major defects (size out of tolerance, hardware malfunction, coating damage on visible faces) and 4.0 for minor defects.
| Lot size (units) | Sample size | Accept / reject at AQL 2.5 major | Accept / reject at AQL 4.0 minor |
|---|---|---|---|
| 91–150 | 20 | 1 / 2 | 2 / 3 |
| 151–280 | 32 | 2 / 3 | 3 / 4 |
| 281–500 | 50 | 3 / 4 | 5 / 6 |
| 501–1,200 | 80 | 5 / 6 | 7 / 8 |
Write the inspection into the contract: who pays, which defects are critical, and that the balance or L/C presentation requires a passed report. Budget roughly USD 300–500 per person-day in South China; a 40HQ of windows usually needs one to two person-days.
What to inspect on windows specifically
Generic consumer-goods checklists miss most window defects. Give the inspector your signed shop drawings and a product-specific list so that the report is measured against your order, not against the factory's catalogue.
- Dimensions and squareness: overall width and height against the shop drawing, and diagonals within the agreed tolerance, typically 2 mm on units up to 2 m.
- Glass: build-up, Low-E position, safety marking on toughened or laminated panes, and no scratches or seal failures in the IGU.
- Coating: RAL colour against the approved sample, dry film thickness with a gauge (60–80 µm is typical for powder), and no damage on visible faces.
- Hardware: brand and model as specified, smooth operation, locking points engaging, and correct handing.
- Labels and packing: unit tag matching the drawing, CE, NFRC or other labels where required, and crates marked and protected for the voyage.
Frequently asked questions
- How can I tell if a Chinese window supplier is a factory or a trading company?
- Look up its Unified Social Credit Code on China's national enterprise credit system and read the business scope: manufacturers list production or processing of aluminium products, doors and windows; traders list sales and import-export. Then confirm the registered address matches the plant shown in a live video audit and that test reports and the bank account belong to the same legal entity.
- How do I verify a window test report from China?
- Check that the report shows the lab name, report number, issue date, applicant, tested system, specimen size and results by class. Email the lab directly, using contact details from its own website rather than the report, and ask it to confirm the report number and applicant. Reports issued to another company or for a different system should not be accepted.
- Is a video factory audit enough?
- For many first orders a well-run live video audit is sufficient if combined with a cut corner sample, verified test reports and a third-party pre-shipment inspection. The call should be scheduled at short notice, last at least 60 minutes and walk continuously through extrusion or profile store, coating, CNC, assembly, testing and packing. Large projects justify an on-site visit.
- What AQL should I use for window inspections?
- A common plan is ISO 2859-1 general inspection level II with AQL 0 for critical defects, 2.5 for major defects and 4.0 for minor defects. Define each category in writing before production: for example wrong glass type is critical, a size outside tolerance is major, and a small scratch on a hidden face is minor. Agree that the balance payment depends on passing.
- How much does a third-party inspection cost in China?
- Pre-shipment inspections by firms such as SGS, Bureau Veritas or Intertek in South China typically cost around USD 300–500 per person-day, plus travel in some cases. A 40HQ container of windows usually needs one to two person-days. Full factory audits against a structured checklist cost more because they take longer and produce a scored report.
Sources & standards
- 01Inspection, audit and testing services — SGS
- 02Supplier audits and pre-shipment inspection — Bureau Veritas
- 03Supplier assurance and product inspection — Intertek
- 04ISO 2859-1 sampling procedures for inspection by attributes — International Organization for Standardization
- 05Qualicoat licensees and specifications — Qualicoat
