Plywood is made by glueing together thin sheets of wood veneer. The thickness of an individual sheet is 1.4 – 3.2 mm. The sheets are composed so that the directions of the grain of the superimposed sheets are usually perpendicular to each other. In birch plywood board, there is usually an odd number of sheers (at least three), so the direction of grain of the surface sheets is always the same. In conifer plywood sheets, the number may also be even. In glueing, weather-resistant phenolic resin adhesive is normally used. In terms of colour, it is considerably darker than veneering wood.
In terms of its basic properties, plywood is comparable to wood. It also has the following benefits, owing to its method of manufacture:
- strength, good at providing rigidity for structures
- dense and shock-resistant
Some plywood products are classified in surface material emissions class M1. Material classification includes the limit values for the emissions of building materials meant for interiors, as well as their classification. Class M1 contains emissions-tested materials, whose emissions of impurities are within the most stringent requirements.