Plywood and Blockboard are two distinct and separate things. In this article we will have a look at the differences between these two types of engineered woods.
The major differences between the two are listed below.
Difference in composition, and the way they are made.
The Plywood sheets that are commonly used in the making of wooden furniture are made from several thin sheets of individual wood veneers (layers/slices of wood). All these layers are firmly pressed and joined with each other to make a plywood sheet. If all these individual layers of wood have been obtained from a hardwood tree, as is usually the case, then the final finished plywood sheet is called a 100% hardwood plywood.
On the other hand, the core of the blockboard is made from solid blocks of wood (These blocks are rectangular elongated blocks/strips obtained from a softwood tree). All these small blocks are of almost the same size, and are arranged end to end to form the entire blockboard core. Then as in the case of plywood, a top and bottom veneer (layer of wooden ply) is bonded/glued over these blocks to form the faces/surfaces.
Externally both plywood and blockboards look similar (especially if you don't look at the board edges), however as the images above amply demonstrate, the composition of block boards is entirely different.
Difference in the way they are used.
While plywood is suitable for most furniture making requirements, it has a tendency to sag or bend when very lengthy pieces are used. In such cases using blockboards is preferred over using plywood.
For example, when longer pieces of wood is required in furniture such as for long tables, or settees (diwan) and for benches which will have to bear some load, blockboards are preferred over plywood. Other common uses of blockboard include making of doors, panels, and partitions.
Difference in material.
Good quality commercial and marine plywood is made using hardwood veneers which is denser and heavier than softwood. Hardwood is considered to be a stronger and more durable material than softwood. An example of hardwood is teak wood, or Gurjan wood.
Blockboards usually have a core made of softwood blocks (for example the wood of a mango tree) sandwiched between hardwood veneers. Sometimes two veneers are used on either side to make the blockboard stronger. The softwood core makes the board lighter in weight, and still the use of solid wooden blocks ensures that the board is strong enough to withstand a substantial amount of load.
Differences in workmanship
Unlike plywood which is uniform throughout its length and breadth, the blocks of a blockboard may have minor gaps between them, that cannot be seen from the outside. Because of this nails that are hammered in the boards (for example for attaching a frame to the board) can sometimes go into these gaps instead of the solid wood. However this is not usually a major drawback.