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Blockboard and Flush Doors - Similarities and differences

In this article we will take a look at the similarities and differences between Blockboard and Flush Doors.


Blocks inside a blockboard
The damaged backrest of a wooden bench revealing the blocks inside the blockboard. Photographed at a small tea shop in Navi Mumbai, India.

The core of blockboard is made from solid blocks of softwood (e.g. strips of pine wood are used). This core is sandwiched between veneers on either side. Usually a single layer of ply is used for both the front and back faces of the board.

Blockboards are light in weight compared to hardwood plywood or solid wood, and often used for making furniture such as long bookshelves, tables and benches, and doors.

Blockboards are manufactured in interior as well as exterior grade, and are suitable for all furniture applications that require longer pieces of wood that can take some weight and which will not bend in the middle.

The image alongside shows the blocks inside a blockboard.

Flush Doors

Flush doors, as the name implies, is a popular material used for making interior and exterior doors. Flush doors are of two types:

1. Solid core flush door and

2. Hollow core flush door.

Flush Door edge
An unfinished solid core flush door photographed at a carpenters shop in Navi Mumbai. Notice the solid blocks that line the edge of the door.

The solid core flush doors are very similar to blockboards, that have solid blocks of softwood covered on both sides by thin layers of plywood. The doors are not too heavy (so transportation during installation becomes easier), are of decent strength, and do not sag or bend easily. Most of the doors that we use for our homes are actually flush doors.

There is some slight difference between blockboard doors and flush doors though. Blockboards have a slightly thicker layer of ply on the surface (3 to 4 mm), while flush door surfaces have ply (veneer) of just about 2.5 mm. My understanding is that this is because the density of blockboards needs to be increased compared to doors, as these boards will have to bear some weight when used in furniture and hence need to be a bit stronger.

The second type, hollow core flush doors are not blockboards. They do not have a solid block core and are hollow on the inside, having just a bit of supporting structure (honeycomb shaped) or having paper or particle board material on the inside. The outer layers are as usual made up of regular ply/veneer. These hollow types of flush doors are commonly used to make partitions.

The advantage of using blockboard doors (solid core flush doors) is that the material has good dimensional stability and stiffness, but still is lighter in weight and is cost-effective. Plywood is rarely used for doors (since it has the tendency to bend). The other option is using good quality solid wood doors, such as teak wood doors which are much better and stronger then blockboards, but these are quite expensive.