Section Contents

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 1-09 Structural Plywood and US PS 2-10 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.

APA in Europe Wizard

All Questions OSBPlywood

What is a ‘life cycle stage’ and how do these link to the environmental assessment of whole buildings?

How do core category rules link with environmental product declarations?

Whose responsibility is it to check that wood products being imported into the EU do not originate from illegally sourced timber supplies?

Does the EUTR require mills to provide any extra documentation for customs entry into the European Union?

Must all plywood and OSB panels carry a CE marking?

What is the definition of a construction product under the CPR?

What is a Declaration of Performance referred to under the Construction Products Regulation?

What is the difference between Structural 1 and Exposure 1?

Does structural panel siding have shear values?

What are mould and mildew, and do they compromise the integrity of engineered wood?

The CE-mark on an APA plywood panel means it conforms to European Standards – but which ones?

I want to use a Rated Sheathing panel for flooring/ roofing application, what info do I need to know?

Plywood: Span rating
OSB: Span rating

What extra strength benefits do Structural 1 OSB panels provide over standard Rated Sheathing panels?

Do APA panels give off formaldehyde?

Plywood: Formaldehyde
OSB: Formaldehyde

What is the difference between a touch-sanded panel and sanded panel?

I’d like to know how APA veneer grades match those given in the European standards

How do I correctly gauge the face appearance a plywood Siding panel?

I want to specify an APA panel for concrete formwork – what do I need to know?

Are APA panels tongue and grooved on all four edges?

I am not familiar with the term ‘Sized for Spacing’ – what is its significance?

How are Performance Category and thickness related?

I’d like to know more about a panel’s Span Rating and how it links to thickness.

Plywood: Span rating
OSB: Span rating

What is Span Rating on the APA trademark and why is it important?

Plywood: Span rating
OSB: Span rating

What is the difference between Exposure 1 and Exterior plywood panels? What are their appropriate uses?

What are the main OSB panels likely to be available in Europe?

What are the main plywood panels likely to be available in Europe?

What are the main European standards that I would need to be aware of for OSB panels?

The main standards are: EN 13986 and EN 300

What are the main European standards that I would need to be aware of for plywood panels?

The main standards are: EN 13986, EN 636, EN 314, EN 635-3