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EN 324-1

EN 324 -1: 1993

Wood-based Panels – Determination of thickness, width and length

Part 1 gives methods for measuring the thickness, width and length of wood-based panels.  It applies to whole flat boards.


  • A micrometer or similar measuring instrument having flat, parallel measuring surfaces of 16mm (± 1) diameter and an operating force of 4N (± 1) and graduated to allow readings to 0.05mm.  Measurements are taken at approximately 50mm from the panel edges at points in each corner and in the middle of each side – 8 no. points in total per panel.  Readings must be within 1% of the thickness but to be not less than 0.1mm.  Average the 8 no. readings and express this figure to the nearest 0.1mm.

Length and width

  • Measure both the length and width of each panel along two lines parallel to and at a distance of 100mm from the edges to an accuracy of 0.1% but not less than 1mm.  Average the two readings each for length and width and express the results to the nearest 1mm.

In comparison – APA’s method for calculating the thickness, length and width:


  • Measure using a micrometer having anvils of diameter 19.1mm (+1.3mm/ – 0) or 3/4” (+ 0.05”/ -0) and an anvil pressure of not less than 34 kPa (5 psi) and not more than 69 kPa (10psi).
  • Measure mid-width on one end of a panel.  If the measurement is below minimum or above maximum requirements, then three additional measurements shall be taken – one at approximately mid-width on the opposite end and one at approximately mid-length on each side of the panel.
  • Calculate the average of these 4 readings. If the average lies between the minimum and maximum thickness for that specific performance category, then the panel is acceptable; if it is outside the minimum or maximum tolerance, then the panel is below/above thickness.

Performance Category thickness and tolerance for APA plywood panels

This is in line with US PS 1-19 Structural Plywood and US PS 2-18 Performance Rated OSB.

APA Plywood










±0.016 (1/64)




Touch sanded




±0.031 (1/32)




Length and width

  • A tolerance of + 0mm, – 1.6mm (1/16”) should be allowed on the specified length and width.