Tongue and Groove Flooring Is Standard. But What Is It?

Hardwood Floor Installation
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Some unknown genius, many years ago, invented it and we are still using it today.  Even as the range of flooring materials has expanded beyond classic solid hardwood into other areas--laminate and engineered, notably--this ancient technique is still in use today.

What did this insanely smart genius invent?  A simple process of joining materials called tongue and groove.

Defined:

Tongue and groove is used in conjunction with wood floorboards, sheet paneling, wainscot, and any number of other materials where a tight, solid seam is required between separate pieces.

Tongue and groove means that each piece has a tongue side and a groove side.

The tongue and the groove each run the entire length of the piece. One tongue fits snugly into the groove of the adjoining board.

Tongue and Groove's Floating Off-Shoot:  Lock and Fold

Basic tongue and groove joinery is a straight tongue that horizontally slides into a straight groove.

To prevent the boards from moving, nails or flooring staples are driven into the tongues.  These fasteners attach directly to the sub-floor.

As laminate flooring manufacturers developed new ways of joining boards, a slightly different technique came about--floating floors.  Floating floors attach only to themselves, from one board to the next, not the sub-floor.

At first, glue was used to join tongues to grooves.  But an easier method, lock and fold, was developed to allow tongues to fit into grooves with no glue, no fasteners.  

Advantages

  1. Tight join, requiring minimal amount of nailing or gluing to hold together.
  1. Provides microscopic seams.
  2. With proper coating, tongue and groove can even be water-tight.

Disadvantages

  1. Can be difficult to fit the tongue into grooves, especially with boards have become swollen due to humidity.
  2. Tongues can easily break off, unless special care is taken.
  3. Difficult, if not impossible, to disassemble pieces that have been joined with tongue and groove. Tongue and groove wood floors usually cannot be disassembled without significant breakage.