(BS) EN 300 : 2019
Oriented Strand Boards (OSB) – Definitions, classification and specifications
This defines the terms, establishes a classification and specifies requirements for OSB. The values appearing in this standard relate to the products properties but they are not characteristic values to be used in design calculations.
See OSB Use Classes and durability issues – this was retained from the now withdrawn EN 335-3:1995 for OSB.
The methods for determining the mechanical properties for structural purposes are given in EN 789. The method of determining the characteristic values of these mechanical properties and the density for the use of OSB in structural applications is given in EN 1058. Design characteristics for OSB can also be taken from EN 12369-1. For thicknesses up to 25mm, tests have to be performed to EN 789 & EN 1058.
The four types of panel classification used in this standard are:
| OSB Type | Definition |
|---|---|
| OSB/1 | General purpose, non load-bearing panels, and panels for interior fitments for use in dry conditions |
| OSB/2 | Load-bearing panels for use in dry conditions |
| OSB/3 | Load-bearing panels for use in humid conditions |
| OSB/4 | Heavy duty load-bearing panels for use in humid conditions |
This standard gives the general requirements for all types of OSB as well as appropriate test methods.
The values given in Tables 2 to 7 of this standard are for use in factory production control and must not be used for design calculations. The test methods by which these values for specified mechanical and swelling properties are determined are also listed in these tables.
The requirements in Tables 2 to 7 are 5 percentile values (95 percentile values in the case of swelling in thickness) based on the mean value for individual panels and calculated according with EN 326-1, or for continuous factory production control, EN 326-2.
How factory production control is to be carried out is given along with details of marking requirements. This references the harmonised European standard for wood-based panels, EN 13986.
Supplementary properties for use of OSB and the appropriate test methods are given in Annex C (normative). These cover dimensional changes, mechanical properties and performance properties.
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. |
