Plywood is a sheet material made from multiple thin layers of wood (veneer) glued together in alternating grain directions. Thanks to this cross-laminated construction, plywood is strong in all directions, barely warps, and is more stable than solid wood. It is widely used as roof decking, flooring, furniture panels, and structural sheathing.
How is plywood made?
1. A log is rotary-peeled on a lathe into thin sheets (veneer, 1-3 mm thick)
2. The sheets are dried
3. They are glued together in alternating grain directions (rotated 90°) under high pressure
4. The result is a stable panel with an odd number of layers (3, 5, 7, 9…)
The cross-laminated grain is the secret: where solid wood normally moves in one direction (shrinks/swells), plywood counteracts this because the layers restrain each other’s movement.
Types of plywood
| Type | Wood species | Waterproof | Application |
|---|---|---|---|
| Interior plywood | Poplar, beech | No | Furniture, interior walls |
| Structural plywood | Spruce, poplar | Limited | Roof decking, flooring, formwork |
| Marine plywood (WBP) | Okoumé, meranti | Yes (waterproof bonded) | Exterior use, boat building |
| Birch plywood (Finnish) | Birch | Limited | Furniture, exposed surfaces, worktops |
| Film-faced plywood | Various + film coating | Yes | Formwork (reusable) |
Standard dimensions
| Sheet | Thicknesses (mm) |
|---|---|
| 122 x 244 cm (standard) | 4, 6, 9, 12, 15, 18, 24 mm |
| 125 x 250 cm | Same |
Plywood for DIY projects
Roof decking
18 mm structural plywood on the rafters as a base for EPDM or bitumen. The sheets are screwed to the rafters, with 2-3 mm gaps for expansion.
Flooring
18-24 mm plywood as subfloor or as a visible floor (sanded + lacquered). Birch plywood looks best as an exposed finish.
Furniture
- Cabinets — 18 mm birch or poplar plywood
- Worktops — 24 mm birch plywood (strong and flat)
- Shelves — 18 mm, depending on span
Wall and ceiling cladding
9-12 mm plywood as panelling, optionally with a visible veneer face.
Plywood vs. OSB vs. MDF
| Plywood | OSB | MDF | |
|---|---|---|---|
| Construction | Cross-laminated veneer | Oriented strands | Fine wood fibres |
| Strength | High | Good | Moderate |
| Moisture resistance | Good (WBP variant) | Moderate | Poor |
| Exposed use | Yes (attractive veneer) | No (rough) | Yes (smooth, paintable) |
| Price | Higher | Lower | Lower |
| Weight | Medium | Medium | Heavy |
Related terms
- OSB board
- Roof decking
- Timber frame construction