Plywood
Plywood and multiplex boards: veneer layers, bonding classes, density, common thicknesses, standards and uses for bracing.
from 5 layers and above 12 mm also called multiplex
A board glued from thin veneers, with the grain of each layer crossing the next. The crossing prevents the timber from moving and gives strength in all directions – which makes plywood an excellent bracing material.
How is it made?
Rotary-cut veneers about 3 mm thick are dried, coated with adhesive, stacked with each layer turned by 90° and hot-pressed. The number of layers is odd (3, 5, 7 or 9) so that the board is symmetrical. The adhesive is MUF or PF, about 3% by volume.
Boards are also classified by their bonding: there are versions for dry interior conditions, for occasional moisture and for permanent moisture.
Technical data
- Build-up
- 3, 5, 7 or 9 layers of rotary-cut veneer approx. 3 mm thick, crossed layer by layer
- Raw material
- spruce, pine and maritime pine, Douglas fir, hemlock; beech
- Strength
- depends on the class according to EN 636, 5–120 N/mm²
- Density
- 450–580 kg/m³ (softwood), 720–780 kg/m³ (beech)
- Adhesive
- MUF or PF (approx. 3% by volume)
- Common sizes
- thickness 8–33 mm; boards usually 125 cm wide
- Standard
- EN 636, EN 13986
- What is it for?
- load-bearing and bracing sheathing for walls, floors and roofs
| Format (mm) | Thickness (mm) | Layers |
|---|---|---|
| 2500 × 1250 (common), 2440 × 1220 | approx. 8–40 | 3, 5, 7, 9 … (multiplex: from 5 layers, above 12 mm) |
Based on retailer ranges; exact sizes are given by the manufacturer.
Applications
- load-bearing and bracing sheathing on walls, floors and roofs
- load-bearing floor and wall elements; beech plywood has particularly high strength
- weather-resistant cladding, formwork, scaffolding, interior design
What to watch out for
- Outdoors, only boards with suitable bonding may be used, and even then their edges are sensitive to moisture – they must be covered or sealed.
- The bonding class must be chosen for the location (dry interior, occasional or permanent moisture).