A pre-shipment inspection checklist for wall panels sets the sampling plan (usually AQL-based under ISO 2859-1 or ANSI/ASQ Z1.4), then checks quantity, dimensions, colour against the signed master sample, slat bonding, surface defects, packaging, labels and documents. It is done when production is finished and most goods are packed, before the balance is paid.
Key takeaways
- Agree the checklist, tolerances, defect classes and AQL levels with the factory before production starts, not on inspection day.
- The signed master sample is the reference for colour, sheen and finish. Without one, colour disputes have no objective answer.
- For slat panels, the high-risk checks are slat straightness and spacing, slat-to-felt bonding, colour consistency across batches, and corner protection in the cartons.
- A good report has photos for every check, measured values (not just pass/fail) and a clear list of defects found.
- A third-party inspector gives an independent result; tie the balance payment to it.
Last reviewed: October 2026 by the Linegrain specification team.
What is a pre-shipment inspection?
A pre-shipment inspection (PSI) is an on-site check of finished goods before they leave the factory. Inspection company QIMA describes it as usually taking place when at least 80% of the order is complete and packing has begun, which leaves time to correct problems before loading (QIMA, Pre-shipment inspection). The inspector draws a random sample, checks it against the agreed specification and issues a report with photos and a pass, fail or pending result.
For wall panels, a PSI matters more than for many products, because defects such as colour drift, bowed slats or weak bonding are expensive to put right once panels reach a site in another country.
How does AQL sampling work?
Inspectors do not check every panel. They use acceptance sampling: a sample size is chosen from the lot size, and the lot is accepted or rejected depending on how many defective units are found in the sample.
The standards
The international standard is ISO 2859-1, Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection. Its third edition was published in January 2026, replacing the 1999 edition and its amendments, and adds skip-lot sampling procedures alongside switching rules for tightened and reduced inspection (ISO 2859-1:2026). Many inspection companies, including QIMA, sample to ANSI/ASQ Z1.4, an AQL-indexed attribute sampling standard with normal, tightened and reduced plans (ASQ, Z1.4 and Z1.9). Name the standard and edition in your purchase order so both sides use the same tables.
Reading a sampling plan
A plan has three parts: the inspection level (for example General Inspection Level II, used in the example below), the sample size code letter that follows from the lot size, and the accept/reject numbers for each AQL. QIMA gives a worked example: a 4,000-unit shipment at General Inspection Level II gives code letter L, which at AQL 2.5 means inspecting 200 units, accepting the lot with 10 or fewer defective units and rejecting it with 11 or more (QIMA, AQL). Your inspector will look up the plan for your actual lot size.
Defect classes
Defects are classed as critical (safety or compliance failures), major (likely to cause a return or rejection) and minor (small cosmetic issues). According to QIMA, the AQL for critical defects is typically zero, AQL 2.5 is common for major defects on general consumer goods, and AQL 4.0 is used where minor cosmetic defects are acceptable. For slat panels, agree with your supplier which defects fall in each class; the table below is a starting point.
| Check | Method | Typical defect class if failed |
|---|---|---|
| Wrong finish, board grade or missing compliance label | Compare against PO and master sample; check labels | Critical |
| Panel length, width, thickness outside tolerance | Tape, steel rule and caliper on each sampled panel | Major |
| Slat spacing uneven or slats not parallel | Measure gap at both ends and centre; straight edge | Major |
| Slat lifting or loose from felt | Hand pressure along each slat; flex test at panel ends | Major |
| Colour or sheen visibly different from master | Side-by-side under daylight-equivalent light; optional spectrophotometer | Major |
| Bowing or twist | Panel on flat table; measure gap at worst point | Major |
| Chipped slat end, scratch, glue mark | Visual at arm’s length under good light | Minor or major, by size and position |
| Carton damage, missing corner protection | Inspect sampled cartons before opening | Major |
| Wrong carton marks or barcode | Check against artwork and packing list; scan barcodes | Major |
What should the checklist cover for slat panels?
1. Quantity and packing list
- Count cartons and pallets against the packing list, by finish and size.
- Check how much is finished, packed and still in production.
- Confirm each pallet’s label matches its contents.
2. Dimensions and geometry
- Measure length, width and total thickness on every sampled panel. For a Linegrain standard acoustic slat panel the nominal size is 2400 × 600 × about 21 mm; use the tolerances in your specification.
- Measure slat width and gap width at both ends and the middle. Standard slats are about 27 mm wide with about 13 mm gaps.
- Check squareness (diagonals) and bowing on a flat table.
- For 2700 and 3000 mm panels, such as the extended-height slat panel, check bowing along the full length.
3. Colour, sheen and finish against the master
- Lay sampled panels beside the signed master sample under daylight-equivalent lighting. Check colour, grain direction, sheen and texture.
- Compare panels from different production days or veneer bundles, not only against the master. Batch-to-batch variation shows up on the wall.
- If you use instrument measurement, agree the formula and the limit in advance. ISO/CIE 11664-6 specifies the CIEDE2000 colour-difference formula (ISO/CIE 11664-6:2022); the acceptance limit itself is a commercial agreement between buyer and supplier, and natural veneer will vary more than laminate. Our veneer vs laminate guide explains why.
4. Bonding and construction
- Press along each slat to check it is fully bonded to the felt. Lift the panel by one end and flex it slightly: slats should not move.
- Check for glue squeeze-out in the gaps and on the felt.
- Confirm the board core matches the order (for example E1, CARB P2 or fire-retardant MDF) using the factory’s material records and board labels. A cut sample can show a fire-retardant core’s colour where relevant.
- Check felt colour and thickness.
5. Surface defects
- Inspect at a set distance and under set lighting, as agreed in the checklist, so “visible” means the same thing to both sides.
- Record chips, scratches, dents, lacquer runs, dust inclusions, veneer splits and open joints, with location and size.
6. Packaging and labelling
- Check carton strength, corner and end protectors, and protective sheets between faces.
- Check carton marks, barcodes, batch codes and private label artwork against approved files.
- For the US, confirm country-of-origin marking on articles or containers, as required under 19 CFR Part 134, and TSCA Title VI labels for MDF-based products.
- Check solid wood pallets carry an ISPM 15 mark.
- Do a drop or handling check on a sampled carton if your route includes parcel or LTL delivery.
7. Documents
- Commercial invoice and packing list match the goods inspected.
- Formaldehyde certificates, fire and acoustic test reports relate to this build. Check that the product described in each report matches the board, finish and felt you ordered.
- Material records for board, finish and felt batches.
What should the photo report include?
A useful report lets you decide without travelling to the factory:
- Summary: result, sampling plan used, lot size, sample size, and defects found by class.
- Measured values for each sampled panel, not only “conform”.
- Photos of every check: overview of the goods, cartons and labels, measurements with the tool reading visible, master sample comparison, and close-ups of each defect with a scale reference.
- Pallet and carton photos as packed, and the loading count if loading supervision is booked.
- Inspector’s notes on anything outside the checklist.
Should you use a third-party inspector?
A factory’s own QC team checks continuously during production, and that remains essential. A third-party inspector adds independence: they report to you, follow your checklist and have no stake in the shipment leaving on time. Many buyers use both, with the factory’s in-line checks during production and a third-party PSI at the end. If the result is a fail, agree in advance whether the factory sorts and reworks the lot, followed by a re-inspection, and who pays for it.
Linegrain works through audited partner factories; our quality and testing page sets out how we approach quality. For the sourcing steps before inspection, see how to import acoustic panels from China, and for timing, the MOQ, lead time and shipping guide.
FAQ
When should a pre-shipment inspection be done?
When production is complete and most goods are packed. QIMA describes the usual point as at least 80% complete with packing started, which leaves time for rework before loading.
Which AQL should I use for wall panels?
A common starting point is zero for critical defects, 2.5 for major defects and 4.0 for minor defects. Agree the levels, the inspection level and the defect classes with the supplier before production.
How do I check colour consistency?
Compare sampled panels with the signed master sample and with each other under daylight-equivalent lighting. For instrument checks, agree the colour-difference formula (such as CIEDE2000) and the limit in advance.
Is ISO 2859-1 the same as ANSI/ASQ Z1.4?
Both are AQL-indexed attribute sampling standards for lot-by-lot inspection. Name the standard and edition you want used in the purchase order so the inspector applies the right tables.
Want an inspection checklist written into your order? Request a quote and we will include the tolerances, master sample process and packaging specification for your panels.