OSB Wood Panel
What is OSB?
Oriented Strand Board (OSB) is a widely used, versatile engineered wood panel made using waterproof heat-cured adhesives and rectangular shaped wood strands that are arranged in cross-oriented layers. It is similar in strength and performance as plywood, resisting deflection, warping and distortion.
How is OSB made?
OSB is made from wood strands 8 to 15 centimeters long. It uses the whole tree and makes use of crooked, knotty and deformed trees that would otherwise go unused. In BC, OSB is made from abundant, small diameter poplar and aspen trees. As strands, they are mixed with waterproof resin and interleaved together in thick mats, which are then bonded together under heat and pressure. BC manufacturers use a variety of different fabrication processes to deliver a spectrum of OSB products. The result is solid, uniform building panels, with enhanced features, and high strength and water resistance.
Oriented Strand Board Physical Property
a) Climate
Like other wood-based panel products, OSB is hygroscopic and its dimensions change in response to a change in humidity. A 1% change in moisture content increases or decreases the length, width and thickness of the different grades of OSB by the amounts set out in the table below.
Type of panel |
Specification |
Dimensional change at 1% change in panel moisture content |
||
Length %
|
Width %
|
Thickness %
|
||
OSB
|
EN 300, OSB/2
|
0.03
|
0.04
|
0.7
|
EN 300, OSB/3
|
0.02
|
0.03
|
0.5
|
|
EN 300, OSB/4
|
0.02
|
0.03
|
0.5
|
Relative humidityat 20° C |
Approximate equilibrium moisture content |
30%
|
5%
|
65%
|
10%
|
85%
|
15%
|
OSB must be conditioned to bring it into equilibrium with its environment before it is fixed. This is usually achieved by loose stacking of the panels in the room where they will be used prior to fixing them. The time required for the panels to achieve equilibrium moisture content will vary depending upon the temperature and relative humidity in the building. The likely equilibrium moisture content levels of OSB in various conditions are as follows:
In a building with intermittent central heating: 8-10%
In an unheated building: up to 15%
b) Biological attack
Typically OSB will not be attacked by wood-boring insects common in temperate climates. It can be used in hazard classes 1, 2 and 3 as defined in EN 335-1 “Durability of wood and wood-based products — Part 1: Definition of hazard classes of biological attack”. For these three hazard classes, the respective moisture content of OSB and the organisms that may attack OSB under the specified conditions are given in EN 335-3 “Durability of wood and wood-based products — Part 3: Application to wood-based panels”.
c) Water vapour permeability
d) Thermal conductivity
The thermal conductivity (l ) of OSB is 0.13 W/m.K for a mean density of 650 kg/m_.
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