Plywood is a widely used and well proven construction material made from a combination of wood veneers and resins. Orientated Strand Board (OSB) is an alternative to plywood in a variety of structural and non-structural applications. Both products are available with full structural data and sustainable credentials.
Specifying Constructional Plywood
Structural Plywood has proof of strength performance provided by the supplier in addition to other product performance
General Plywood has product performance information provided by the supplier but this will not include strength performance data and so should not be used in a structural application.
Both types of constructional plywood can be used in the following uses as defined by the European Standard EN636;
Exterior Use – Permanent outside exposed to the weather – EN 636-3 S (Structural), EN 636-3G (General).
Humid Use – Most construction uses fall into this cateogry as they are covered or rarely exposed to weather, but still at risk of wetting – EN 636-2 S (Structural), EN 636-2G (General).
Dry Use – Interior with no risk of wetting – EN 636-1 S (Structural), EN 636-1G (General).
The most common types of plywood available for use in UK construction are structural plywood for humid uses and general plywood for humid uses. These types of plywood are made from durable resins which are suitable for most construction uses.Please note that no plywood is waterproof! It must always be protected from rain/snow/moisture, by some form of coating or covering, even if only temporarily.
Specifying Constructional OSB
Constructional OSB comes in four grades (technical classes) as defined in the Eurpoean Standard EN 300 and shown in the list below. The standard specifies the requirements for OSB for general purposes or structural applications in dry and humid conditions. Selection of a grade of load-bearing panel is dependent upon the ambient climatic conditions together with the level of loading that is anticipated:
OSB/1 – General purpose boards and boards for interior fitments (including furniture) for use in dry conditions. Should not be used in a structural condition.
OSB/2 – Load-bearing boards for use in dry conditions.
OSB/3 – Load-bearing for use in humid conditions.
OSB/4 – Heavy-duty load-bearing boards for use in humid conditions.As with structural plywood, Structural OSB (OSB 2/3/4) has proof of strength of performance provided by the supplier in addition to other product performance information. As with plywood OSB that is used in construction must comply (by law) with the Construction Products Directive (CPD) and the recommended way to achieve this is by compliance with the Harmonised Standard for wood based panels (EN13986); the standard calls up EN 300 for OSB. A ‘CE’ logo may be present as an indication that the OSB meets the requirements of the European Standard EN 13986.