How to Check Plywood Quality at Delivery: 10 On-Site Tests

The 10 Checks

1. Count and sizes

Confirm the quantity, grade and sheet size on the delivery note against your order. Standard sheets are 8 × 4 ft.

2. Thickness at several points

With a caliper or vernier, measure each sampled sheet at four edges and the middle. Take sheets from the top, middle and bottom of the stack. Variation within a sheet or across the lot is a sign of poor calibration. ZIPCO® calibrated products are checked to a ±0.15mm tolerance, so differences well beyond that are worth raising.

3. Sheet weight

Weigh a few sheets. For reference, an 8 × 4 ft ZIPCO® Calibrated Shuttering Plywood sheet weighs about 24 kg at 12mm and about 35 kg at 18mm. A sheet much lighter than the stated weight may have a thinner or less dense core.

4. Squareness

Measure both diagonals of a sheet. They should be equal within a few millimetres. Unequal diagonals mean the sheet is out of square and will not fit panels cleanly.

5. Flatness

Lay a sheet on a flat floor and look for twist, bow or lifted corners. Sheets stacked badly or taken from poorly dried stock will not lie flat.

6. Edges and core

Look at the edge of a sheet. Core veneers should be continuous and tightly bonded with no visible gaps, overlaps or open layers.

7. Tap test for voids

Tap across the face with a knuckle or a small hammer. A uniform, solid sound is good. A hollow or dull change in sound points to a void or poorly bonded area.

8. Surface and film

On film faced boards the film should be continuous, with no bubbles, torn spots or colour patches. On interior plywood the face veneer should be clean, with no open splits.

9. Moisture and smell

Boards should feel dry. If you have a moisture meter, check a few sheets; ZIPCO® boards are finished within an 8% to 12% moisture range. A damp board or a musty smell suggests poor storage or transit.

10. Batch documents and markings

Match the batch reference on the sheets or packing with the documents. We provide lab test reports, including boiling water test results and density logs, with every batch. Keep one sample sheet from each lot for later comparison.

An Optional Soak Check (Indicative Only)

For waterproof grades, cut a small offcut, soak it in water for 24 hours, then dry and check the edges and glue lines for separation or heavy swelling. This is an indication only. It is not equivalent to the 72-hour boiling water test, which is done in a laboratory. If a soaked offcut falls apart, do not use the lot and ask for the batch report.

When to Hold or Reject a Lot

• Thickness varies well outside the stated tolerance within a sheet or across the lot.
• Weight is clearly below the stated weight for that thickness.
• Visible voids, open core layers, or hollow sounds across many sheets.
• Film that is torn, bubbled or patchy on film faced boards.
• No batch documents, or documents that do not match the delivered grade.

Photograph the problem sheets, note the batch reference, and hold the lot before any cutting. Understanding the grade you ordered helps: see MR vs BWP plywood and how ZIPCO® products are tested.

Frequently Asked Questions