Section Contents

Guide to OSB Use Classes

This guide looks at five key User Classes for OSB.  This information was part of EN 335-3:1995 but is no longer included in a European standard following a recent revision (EN 335:2013).

OSB Use Class definitions

 Use Class
                                               Definitions

 

1

 In this environment, OSB will have a moisture content no higher than that which would result from exposure to an air temperature of 20°C and a relative humidity of 65% for practically the whole of its service life.  They may be regarded as being dry with little risk of attack by surface moulds, staining moulds or wood-destroying fungi.  There is no risk of attack by wood-destroying insects except termites.

 

2

 In this environment, the moisture content of an OSB panel, either in the whole or only in part, can occasionally attain or exceed that which would result from exposure to an air temperature of 20°C and a relative humidity of 90%. The moisture content can occasionally increase to a level which can allow the growth of wood-destroying fungi.  Disfigurement can also occur as a result of the growth of surface moulds and staining fungi. Risk of insect attack is similar to that for Use Class 1.

 

3

 In this environment, OSB can frequently have a moisture content above 20% and thus will often be liable to attack by wood-destroying fungi. Disfigurement can also occur as a result of the growth of surface moulds and staining fungi. Risk of insect attack is similar to that of Use Class 1.

 

4

 In this environment OSB has a moisture content permanently above 20% and is, therefore, liable to attack by wood-destroying fungi. The risk of insect attack to that portion of the panel situated above ground or water is similar to that for Use Class 1. Termites can be an additional problem in certain geographical regions.

 

5

 In this environment, OSB panels are permanently above 20% moisture content and are wholly or partially submerged in salt water. Attack by invertebrate marine organisms is the principal problem. Limnoria spp. and Teredo spp. are problematic in warm waters. Also, the OSB is liable to attack by wood destroying fungi. Risk of insect attack to that portion of the OSB which is above the water level is similar to that for Use Class 1. Termites can be an additional problem in certain geographical areas.

 

APA in Europe Wizard

Close
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